OUTLINE
OF THE INTRODUCTION TO THE DIGITAL DIFFERENTIAL AND INTEGRAL CALCULUS
Konstantinos E.
Kyritsis*
ABSTRACT
In this paper I go
further from the digital continuous axiomatic Euclidean geometry ( [8]) and introduce the basic definitions and derive the
basic familiar properties of the differential and integral calculus without the
use of the infinite, within finite sets only. No axioms are required in this
only successfully chosen definitions. I call it the digital differential and
integral calculus. Such mathematics is probably the old unfulfilled hitherto
dream of the mathematicians since many centuries. Strictly speaking it is not
equivalent to the classical differential and integral calculus which makes use
of the infinite (countable and uncountable) and limits. Nevertheless for all
practical reasons in the physical and social sciences it gives all the well
known applications with a finite ontology which is directly realizable both in
the physical ontology of atomic matter or digital ontology of operating systems
of computers. Such a digital calculus has aspects simpler than the classical
“analogue” calculus which often has a complexity irrelevant to the physical
reality. It can become also more complicated
than the classical calculus when more than 2 resolutions are utilized, but this
complexity is directly relevant to the physical reality. The digital
differential and integral calculus is of great value for the applied physical
and social sciences as its ontology is directly corresponding to the ontology
of computers. It is also a new method of teaching mathematics where there is
integrity with what we say, write, see, and think. In this short outline of the
basic digital differential and integral calculus, we include on purpose almost only
the basic propositions that are almost identical with the corresponding of the
classical calculus for reasons of familiarity with their proofs.
Key
words: Digital mathematics, Calculus
MSC
: 00A05
0.
INTRODUCTION
Changing our concept of
physical material, space and time continuum so as to utilize only finite
points, numbers and sets, means that we change also our perception our usual
mental images and beliefs about the reality. This project is under the next
philosophical principles
1) In the human consciousness we
have the experience of the infinite.
2) But the ontology of the physical
material world is finite.
3) Therefore mathematical
models in their ontology should contain only finite entities and should not
involve the infinite.
4) Strange as it may seem, the digital mathematics are the really
deep mathematics of the physical world, while the classical mathematics of the
infinite ("analogue" mathematics) are a “distant” phenomenology,
convenient in older centuries, but not the true ontology.
This paper is part of larger
project which is creating again the basics of mathematics and its ontology with
new definitions that do not involve the infinite at all.
Our perception and experience
of the reality, depends on the system of beliefs that we have. In mathematics,
the system of spiritual beliefs is nothing else than the axioms of the
axiomatic systems that we accept. The rest is the work of reasoning and
acting.
Quote: "It is not the
world we experience but our perception of the world"
Nevertheless it is not wise to
include in our perception of the material world and its ontology anything else than the finite,
otherwise we will be lead in trying to prove basic facts with unsurpassed
difficulties as the classical mathematics has already encounter , The abstraction of the infinite is
phenomenological and it seems sweet at the beginning as it
reduces some complexity, in the definitions, but later on it turns out to
be bitter, as it traps the mathematical minds in to a vast
complexity irrelevant to real life applications. Or to put it a more easy
way, we already know the advantages of using the infinite but let us learn more
about the advantages of using only the finite, for our perception, modelling
and reasoning about empty space and physical reality. This is not only valuable
for the applied sciences, through the computers but is also very valuable in
creating a more perfect and realistic education of mathematics for the young
people. H. Poincare used to say that mathematics and geometry is the art of
correct reasoning over not-corresponding and incorrect figures. With the digital mathematics this is corrected.
The new digital continuums create a new
integrity between what we see with our senses, what we think and write and what
we act in scientific applications.
The continuum with infinite many points creates an
overwhelming complexity which is very often irrelevant to the complexity of
physical matter. The emergence of the irrational numbers is an elementary
example that all are familiar But there are less known difficult problems like
the 3rd Hilbert problem (see [3] Boltianskii V. (1978)“).
In the 3rd Hilbert problem it has been proved that two solid
figures that are of equal volume are not always decomposable in to an in equal
finite number of congruent sub-solids! Given that equal material solids
consists essentially from the physical point of view from an equal number of
sub-solids (atoms) that are congruent, this is highly non-intuitive! There are
also more complications with the infinite like the Banach-Tarski paradox (see [2]
Banach, Stefan; Tarski,
Alfred (1924)) which is essentially pure magic or miracles making! In other words it has
been proved that starting from a solid sphere S of radius r, we can decompose
it to a finite number n of pieces, and then re-arrange some of them with
isometric motions create an equal sphere S1 of radius again r and by
rearranging the rest with isometric motions create a second solid Sphere
S2 again of radius r! In other words like magician and with seemingly
elementary operations we may produce from a ball two equal balls without tricks
or “cheating”. Thus no conservation of mass or energy!. Obviously such a model
of the physical 3-dmensional space of physical matter like the classical
Euclidean geometry is far away from the usual physical material reality! I have
nothing against miracles, but it is challenging to define a space , time and
motion that behaves as we are used to know. In the model of the digital
3-dimesional space, where such balls have only finite many points such
“miracles” are not possible!
The
current digital version of the differential and integral calculus is based on
the atomic structure of matter as hypothesized 2,000 years ago by the ancient
Greek philosopher Democritus and which has developed in the modern the atomic
physics. Also the role of computers and their digital world is important as it
shows that space, time, motion, images, sound etc can have finite digital
ontology and still can create the continuum as a phenomenology of perception.
The
famous physicist E. Schrodinger I his book ([12] E. Schroedinger. Science and Humanism Cambridge University
press 1961) mentions that the continuum as we define it with the
“analogue” mathematics involving the infinite is problematic and paradoxical,
therefore needs re-creation and re-definition. It is exactly what we do here
with the digital differential and integral calculus.
We
enumerate some great advantages of the digital differential and integral
calculus compared to the classical calculus with the infinite.
1)
The digital continuity
and smoothness (derivative) allows for a variable in scale of magnitude and
resolution such concept and not absolute as in analogue classical mathematics.
A curve may be smooth (differentiable) at the visible scale but non-smooth at
finer scales and vice versa. This is not possible with classical definitions.
2)
Corresponding to the
concept of infinite of classical mathematics in digital mathematics there is
the concept seemingly infinite and seemingly infinitesimal at its various
orders, which is still finite. Thus many unprovable results in classical
mathematics become provable in digital mathematics. This also resurrects the 17th
and 18th century mathematical
arguments in Calculus and mathematical physics that treated the
“infinitesimals” as separate entities in the derivatives.
3)
Many unsurpassed
difficulties in proving desirable results in the infinite dimensional
functional spaces of mathematical analysis disappear and allow for new powerful
theorems because the seemingly infinite is still finite.
4)
Integration is defined as
finite (although seemingly infinite) weighted sum of the volumes of the points
at some precision level, exactly as Archimedes was measuring and integrating
volumes with water or sand. Contrary to classical mathematics any computably
bounded function is integrable (see proposition 3.6 )
5)
Therefore, there are vast
advantages compared to classical analogue calculus. The digital differential and integral calculus is a
global revolution in the ontology of mathematics in teaching and applying them
comparable with the revolution of digital technology of sounds, images .
motion, etc compared to the classical analogue such technologies.
6)
There
are although “disadvantages” too , in the sense that if we do not restrict to a
digital calculus relative 4 precision
levels but include many more and grades of differentiability and integrability
then the overall calculus will become much more complicated than the classical
calculus.
In
this short outline of the basic digital differential and integral calculus, we
include on purpose only the basic propositions that are almost identical with
the corresponding of the classical calculus for reasons of familiarity with
their proofs. An exception is the proposition 3.6 which has an almost obvious
proof.
1.
THE
DEFINITION OF THE DIGITAL REAL NUMBERS
THE MULTI-PRECISION DECIMAL DIGITAL REAL NUMBERS R(m,n,p,q)
Creating 3D mental images with the imagination
The physiscists andd nobel prize winner R Feynamnn often was explaining that he was training his imagination imagining in 3D mental images the moving molecules of a gas in box, and perceiving that temperature as their avearge velocity, the ressure as the average moemntum of the walls of the box, and the density as the average number of particles per unit of volume, He was explaing that he was getting much pleasure from this spiritual excerise of craeting 3D mental images and simulating the reality.
Excatly this 3D VISUAL MENTAL IMAGES LANGUAGE parctice is UTILIZED BY ME AND is required by someone to understand and develop the digital or natural mathematics, in geometry, real numbers and analysis.
Rules for phantasy and drawing of figures.
As initially we considered a system of digital real numbers R(m,n,p,q) we consider the points of P(m), P(n) as visible in the figures while the points of P(p) as invisble pixels , and those of P(q) as invisible atoms. Therefore, even the points and seemingly infinitesimals that will be defined below, of P(n) relative to P(m) are considered as visible. This is in accordance with the habit in classical mathematics to make the points visible, although they claim that they have zero size.
a) The rational
numbers Q, as we known them, do involve the infinite, as they are
infinite many, and are created with the goal in mind that proportions k/l
of natural numbers k,l exist as numbers and are unique. The cost of course is
that when we represent them with decimal representation they may have infinite
many but with finite period of repetition decimal digits.
b) The classical
real numbers R, as we know them, do involve the infinite, as they are
infinite many, and are created with the goal in mind that proportions of
linear segments of Euclidean geometry, exist as numbers and are unique (Eudoxus theory
of proportions). The cost of course finally is that when we represent them with
decimal representation they may have infinite many arbitrary different decimal
digits without any repetition.
c) But
in the physical or digital mathematical world, such costs are not acceptable.
The infinite is not accepted in the ontology of digital mathematics (only in
the subjective experience of the consciousness of the scientist). Therefore in
the multi-precision digital real numbers, proportions are handled
in different way, with priority in the Pythagorean-Democritus idea of the creation
of all numbers from an integral number of elementary units, almost exactly
as in the physical world matter is made from atoms (here the precision level of
numbers in decimal representation) and the definitions are different and more
economic in the ontological complexity.
We will choose for all practical applications of the digital real numbers
to the digital Euclidean geometry and digital differential and integral
calculus, the concept of a system of digital decimal real numbers with three
precision levels, lower, low and a high.
Definition 1.1 The definition of a
PRECISION LEVEL P(n,m) where n, m are natural numbers , is that it
is the set of all real numbers that in the decimal representation have
not more than n decimal digits for the integer part and not more than m digits
for the decimal part. Usually we take m=n. In other words as sets of real
numbers it is a nested system of lattices each one based on units of power
of 10, and as union a lattice of rational numbers with finite many decimal digits.
We could utilize other bases than 10 e.g. 2 or 3 etc, but for the sake of
familiarity with the base 10 and the 10 fingers of our hands we leave it
as it is.
THE DEFINITION 1.2 OF THE
DIGITAL REAL NUMBERS R(m,n,p,q)
Creating 3D mental images with the imagination
The physiscists andd nobel prize winner R Feynamnn often was explaining that he was training his imagination imagining in 3D mental images the moving molecules of a gas in box, and perceiving that temperature as their avearge velocity, the ressure as the average moemntum of the walls of the box, and the density as the average number of particles per unit of volume, He was explaing that he was getting much pleasure from this spiritual excerise of craeting 3D mental images and simulating the reality. Excatly this 3D VISUAL MENTAL IMAGES LANGUAGE parctice is UTILIZED BY ME AND is required by someone to understand and develop the digital or natural mathematics, in geometry, real numbers and analysis.
Rules for phantasy and drawing of figures.
As initially we considered a system of digital real numbers R(m,n,p,q) we consider the points of P(m), P(n) as visible in the figures while the points of P(p) as invisble pixels , and those of P(q) as invisible atoms. Therefore, even the points and seemingly infinitesimals that will be defined below, of P(n) relative to P(m) are considered as visible. This is in accordance with the habit in classical mathematics to make the points visible, although they claim that they have zero size.
We assume at least four precision levels
for an axiomatic decimal system of digital real numbers
Whenever we refer to a real number x of a (minimal in precision
levels) system of real numbers R(m,n,p,q) , we will always mean that x belongs
to the precision level P(m) and that the
system R(m,n,p,q) has at least four precision levels with the current axioms.
Whenever we write an equality
relation =m we must specify in what precision level it is
considered. The default precision level that a equality of numbers is
considered to hold, is the precision level P(m).
Some of the Linearly ordered Field operations
The field operations in a precision level
are defined in the usual way, from the decimal representation of the numbers.
This would be an independent definition, not involving the
infinite. Also equality of two numbers with finite decimal digits
should be always specified to what precision level. E.g. if we are talking about
equality in P(m) we should symbolize it my =m , while if
talking about equality in P(q) we should symbolize it by =q .If
we want to define these operation from those of the real numbers with
infinite many decimal digits, then we will need the
truncation function [a]x of a real number a , in the Precision level
P(x).
Then the operations e.g. in P(m) with values in
P(n) m<<n would be
[a]m+[b]m=n[a+b]n (eq.
3)
[a]m* [b]m=n[a*b]n (eq.
4)
([a]m)^(-1)=n[a^(-1)]n (eq.
5)
(Although, the latter
definition of inverse seems to give a unique number in P(n), there may not be
any number in P(n) or not only one number in P(n), so that if multiplied
with [a]m it will give 1. E.g. for m=2 , and n=5 , the inverse
of 3, as ([3]m )^(-1)=n [1/3]n =0.33333
is such that still 0.33333*3≠n1 ).
Nevertheless here we will not involve the infinite and the classical real numbers, and we take the operation of
digital real numbers from the standard operations of them as numbers with
finite digital decimal representation and truncation by rounding.
Such a system of double or triple precision
digital real numbers, has closure of the linearly ordered field operations only
in a specific local way.
That is If a, b belong to the Local Lower precision, then a+b, a*b , -a, a^(-1)
belong to the Low precision level, and the properties of the linearly ordered commutative field hold:
(here the equality is always in P(n), this it is mean the =n).
1) if a, b, c belong to P(m) then (a+b), (b+c), (a+b)+c,
a+(b+c) belong in P(n) and
(a+b)+c=a+(b+c) for all a, b and c in P(n).
2) There is a digital number 0 in P(n) such
that
2.1) a+0=a, for all a in P(n).
2.2) For every a in P(m) there
is some b in P(n) such that
a+b=0. Such a, b is symbolized also
by -a , and it is unique in P(n).
3) if a, b, belong to P(m) then (a+b),
(b+a), belong in P(n) and
a+b=b+a
4) if a, b, c belong to P(m) then (a*b),
(b*c), (a*b)*c, a*(b*c) belong in P(n) and
(a*b)*c=a*(b*c).
5) There is a digital number 1 in P(n) not
equal to 0 in P(n), such that
5.1) a*1=a, for all a in P(n).
5.2) For every a in P(m) not equal to
0, there may be one or none or not only one b in P(n) such
that a*b=1 . Such b is symbolized also by 1/a, and it may not
exist or it may not be unique in P(n).
6) if a, b, belong to P(m) then (a*b),
(b*a), belong in P(n) and
a*b=b*a
7) if a, b, c belong to P(n) then
(b+c) , (a*b), (a*c), a*(b+c), a*b+a*c, belong in P(n)
and
a*(b+c)=a*b+a*c
Which numbers are positive and
which negative and
the linear order of
digital numbers is precision levels P(m), P(n), etc is something known
from the definition of precision levels in the theory of classical real
numbers in digital representation.
If we denote by PP(m) the positive numbers of
P(m) and PP(n) the positive numbers of P(n) then
8) For all a in PP(m), one and only one of
the following 3 is true
8.1) a=0
8.2) a is in PP(m)
8.3) -a is in PP(m) (-a is the
element such that a+(-a)=0 )
9) If a, b are in PP(m), then a+b is in PP(n)
10) If a, b are in PP(m), then a*b is
in PP(n)
It holds for the inequality a>b if and only if a-b is in PP(n)
a<b if b>a
a<=b if a<b or a=b
a>= b if a> b or a=b
and similar for PP(n).
Similar properties as the ones from P(m) to P(n) hold if we substitute n
with m, and m with p, q.
For the R(m,n) the integers of
P(m) are also called computable finite or countable finite, while those of P(n)
are unaccountable finite or non-computable finite or also seemingly infinite
relative to P(m).
Also, the Archimedean property holds only recursively
in respect e.g. to the local lower precision level P(m).
In other words, if a, b,
a<b belong to the precision level P(m) then there is k integer in the
precision level P(n) such that a*k>b. And similarly for the precision levels
P(n) and P(p),P(q).
The corresponding to the Eudoxus-Dedekind completeness in
the digital real numbers also is relative to the three precision levels is
simply that in the precision levels all possible combination of digits are
included and not any decimal number of P(m) or P(n) is missing. Still this
gives
THE SUPREMUM COMPLETENESS
PROPERTY OF THE DIGITAL REAL NUMBERS.
From this completeness we deduce the supremum
property of upper bounded sets (and infimum property of lower bounded sets) in
the P(m) (but also P(n)) precision
levels. This is because in well ordered sets holds the supremum property of
upper bounded sets. Here lower bounded sets have also the infimum property and
this holds for any resolution of the digital real numbers
Mutual inequalities of the
precision levels (AXIOMS OF SEEMINGLY (m,n) -INFINITE OR (m,n)-UNCOUNTABLE
OR NONO-COMPUTABLE FINITE AMONG RESOLUTIONS and seemingly finite or visibly
finite or bounded or computable
finite numbers. )
We impose also axioms for the
sufficiently large size of the high precision level relative to the other two,
and the sufficient large size of the low precision level relative to the local
lower precision level. That is for the mutual relations of the integers m, n, p,
q.
It may seem that these
differences of the resolution or the precision levels are very severe and of
large in between distance, and not really necessary. It may be so, as the
future may show. But for the time being we fell safe to postulate such big
differences.
There are definitions modeled after the definitions of inaccessible cardinals in classical
mathematics. Here we give a weaker alternative definitions with weaker concepts of seemingly infinite that would
correspond to that of inaccessible cardinals. In other words we do not include the operation of power.
We may conceive the countable finite as a finite computable by a
computational power of some computer, and unaccountable finite as the finite
not computable by a type of a computer
Transcendental Orders of (m,n) seemingly infinite, as in classical
mathematics transcendental orders of ordinal numbers are also definable. E.g.
if a, b are (m,n)=seemingly infinite then a is transcendental larger than b, in
symbols a>>b iff b/a=m0
in P(m).
And similarly transcendental orders of seemingly infinitesimals. E.g. if a,
b are (m,n)=seemingly infinitesimals then a is transcendental smaller than b,
in symbols a<<b iff a/b=m0
in P(m).
We may compare them with the small o() and big O() definitions of the
classical mathematics, but they are different as the latter involve the
countable infinite, while former here involve only finite sets of numbers.
9) REQUIREMENTS OF THE
SEEMINGLY INFINITE If we repeat the operations of addition and multiplication of the
linearly ordered commutative field starting from numbers of the precision level P(m), so many times as the
numbers of the local lower precision level P(m), then the results are still inside
the low precision level P(n). In symbols if by |P(m)| we denote
the cardinality of P(m), then
|P(m)|*(10^m), and
(10^m)^|P(m)|<=10^n . Similarly for the pair (m,q). We may express it by
saying that the 10^n is seemingly infinite or unaccountable finite
compared to 10^m, or that the numbers less than 10^n are countable or
computable finite. If we include
besides the addition and multiplication the power operation too, then 10^m is inaccessible
seemingly infinite compared to 10^m (a concept similar to inaccessible
cardinal numbers in classical mathematics). Similarly for the precision levels
P(p), P(q).
10) REQUIREMENTS
OF THE SEEMINGLY INFINITESIMALS The smallest magnitude in
the low precision level P(n) in other words the 10^(-n), will appear as zero
error in the low precision level P(m), even after additive
repetitions that are as large as
the cardinal number of points of the lower precision level P(m) and
multiplied also by any large number of P(m). In symbols
10^(-n)*|P(m)|*10^m<=10^(-m).
Similarly for the pairs (n,p), (p,q).
This may also be expressed
by saying that the 10^(-n) is seemingly infinitesimal compared
to the 10^(-m) . Other elements of P(n) symbolized by dx with |dx|<10^-m
with the same inequalities, that is |dx|*|P(m)|*10^m<=10^(-m) are also
seemingly infinitesimals, provided the next requirements are also met:
The seemingly infinitesimals dx of P(p) relative to P(m) (thus
|dx|<=10^(-m) ) are by definition required to have properties that resemble
the ideals in ring theory (see e.g. [15] VAN DER WAERDEN ALGEBRA Vol I, chapter 3,
Springer 1970 ). More
precisely what it is required to hold is that
If a, b are elements of P(m)
, and dx dy seemingly infinitesimals of P(p) relative to P(n) (thus |dx|, |dy|
<=10^(-n) ,thus relative to P(m) too) then the linear combination and
product are still seemingly infinitesimals. In symbols adx+bdy , are seemingly
infinitesimals of P(n) relative to P(m) and dx*dy is seemingly infinitesimal of
P(q) relative to P(p) and thus relative to P(m) too.
We call this the
ideal-like property of the seemingly infinitesimals.
.
One very important equation is
of course that the digital real numbers is the union of the four precision
levels.
R(m, n, p, q)= P(m)ᴗP(n)ᴗP(p) ᴗP(q)
Two digital systems of Real
numbers R(m,n,p,q) , R(m’,n’,p’,q’) with m=m’, n=n’, p=p’,q=q’ and the above
axioms are considered isomorphic.
SEEMINGLY IRRATIONAL NUMBERS WITHIN THE DIGITAL REAL NUMBERS
The seemingly irrational numbers can be defined as the digital real numbers that have a seemingly infinite number of digits in their decimal representation and cannot be written as quotients of two computable integers (or non-seemingly infinite integers). It is interesting to investigate the the digital real numbers that have a seemingly infinite number of digits in their decimal representation and if there is a period in their decimal representation this period is of a non-computable integer (or non-seemingly infinite integer).
We should point out that in the next considerations, the digital rational numbers, are different from the classical rational numbers, as they do not include classical rational numbers with decimal represation which is of infinite periodic decimal digits. Therefore not only the classical irrational numbers but also some classical rational numbers, may be in the digital real numbers semingly irrational numbers.
Creating 3D mental images with the imagination
The physiscists andd nobel prize winner R Feynamnn often was explaining that he was training his imagination imagining in 3D mental images the moving molecules of a gas in box, and perceiving that temperature as their avearge velocity, the ressure as the average moemntum of the walls of the box, and the density as the average number of particles per unit of volume, He was explaing that he was getting much pleasure from this spiritual excerise of craeting 3D mental images and simulating the reality. Excatly this 3D VISUAL MENTAL IMAGES LANGUAGE parctice is UTILIZED BY ME AND is required by someone to understand and develop the digital or natural mathematics, in geometry, real numbers and analysis.
Rules for phantasy and drawing of figures.
As initially we considered a system of digital real numbers R(m,n,p,q) we consider the points of P(m), P(n) as visible in the figures while the points of P(p) as invisble pixels , and those of P(q) as invisible atoms. Therefore, even the points and seemingly infinitesimals that will be defined below, of P(n) relative to P(m) are considered as visible. This is in accordance with the habit in classical mathematics to make the points visible, although they claim that they have zero size.
2.
THE
DEFINITION OF THE DIGITAL FUNCTIONS, DIGITAL CONTINUITY AND DIGITAL DIFFERENTIABILITY.
A digital
real function at 2 precision levels is a function in the ordinary
set-theoretic sense, that sends elements of the digital real numbers to elements of the digital real umbers. It has
to be defined so that it respects the
precision levels. This is defined so that a parallelogram diagram, of the two functions, the restriction
function and the rounding function commute
in the sense of the theory of categories. Usually the standard way is to define it for the highest resolution
and then extend the definition for the lower resolutions by the rounding function (left for positive
numbers and right for negative numbers). This process is called natural rounding extension on lower
resolutions, and defines the rounded
functions on the lower resolutions so
that the arrow diagrams commute that [f(a)]n =fn([a]n)
if a, f(a) in P(q) and we define f on
P(n) (The rounding of the image is the value of the rounded function on the
rounded argument, so that rounding function and functions commute ). We only need to define the rounding for a
pair of precision levels for differentiation and integration. Here for
P(m)/P(n). The fm is the
rounded function, and it is for all practical purposes the one only function
observed. But it starts from a function f on P(n). So for all digital function
that we will consider, we will conceive them as double functions the finest
of:
P(n)->P(n) and the rounded , f: P(m)->P(m) , and r is the restriction from P(n) to P(m)
then a commutation of diagrams is the [(of([x]m)]m=mf
In
some situations (e.g. definition of continuity) we will assume that the digital
function is defined in 3 precision levels
oof: P(p)->P(p) of: P(n)->P(n) and the rounded ,
f: P(m)->P(m) , and by the restriction from P(n) to P(m)
and from P(n) to P(p) a commutation of
diagrams holds :[(of([x]m)]m=mf and [(oof([x]n)]n=n
of.
And
in some cases we will need all 4-precision levels
For those that feel convenient to start
with the classical mathematics with the infinite, and their functions, digital
functions as above can be obtained by the rounding functions []m []n in the precision levels P(m), P(n). E.g.
starting with the classical exponential function g(x)=ex to obtain a digital function in P(m),
P(n), we use the formulae oof(x)=[e[x]p]p , of(x)=[e[x]n]n and f(x)= [e[x]m]m
DEFINITION 2.1
A digital real function defined on a closed interval f
:[a,b]m ->P(m), of: :[a,b]n ->P(n), oof: :[a,b]p ->P(p) is (digitally)P(m)/P(n)/P(n) continuous at a point x of its domain of
definition [a,b]m in P(m), if and only if for every other point x’
of the domain of definition [a,b]n in P(n), such that x,x’ are of seemingly
infinitesimally distance dx=x’-x
(belongs to P(n)) ,relative to P(m) , then also the dy=of(x’)-of(x) is seemingly infinitesimal of P(n) relative to P(m). It holds in particular:
dy=ndof(x)=mdx=m0
Similar definitions hold for P(m)/P(p), P(n)/P(p) and P(m)/P(q) continuity.
We
concentrate on functions of P(n) of R(m,n,p.q) but we may we not leave unused the precision levels P(p),
P(q). We mention also that the definitions can be also for the triples of
precision levels P(m)-P(n)-P(p), P(n)-P(p)-P(q) as finer forms of continuity. If
it is for all precision levels then it seems equivalent to the classical
definitions.
If digital real function is digitally
continuous at all points of its domain of definition it is called a (digitally) P(m)/P(n) continuous digital
real function.
DEFINITION 2.2
A digital real function defined on a closed interval f
:[a,b]m ->P(m), of: :[a,b]n ->P(n), oof: :[a,b]p ->P(p) is (digitally)P(m)/P(n)/P(p) continuous at a point x of its domain of
definition [a,b]m in P(m), if and only if for every other point x’
of the domain of definition [a,b]p in P(p), such that x,x’ are of seemingly
infinitesimally distance dx=x’-x
(belongs to P(p)) ,relative to P(m) , then also the dy=of(x’)-of(x) is seemingly infinitesimal of P(n) relative to P(m). It holds in particular:
0=mdy=ndof(x)=mdx=m0
Similar definitions hold for P(n)/P(p)/P(q), P(m)/P(p)/P(q) continuity etc.
It
would be nice if it is possible to derive also the digital P(m)/P(n) continuity
as the standard continuity of topological space.
The next definition gives the best idea for such a topological space. A
topological space is defined by its open sets (see e.g. [9] J.Munkress) . But
the open sets can also be definite by the limit points of sets too.
We
consider the Cartesian product set P(m)xP(n) =P(m)xP(n), where we define the
disjoint union space P(m)+P(n) and we do not consider that a coarse
point of P(m) contains fine points of P(n) but we treat them separately. Our topological
space will be the Y=X+oX= P(m)+P(n) . Subsets A of Y can be split to A=oA+cA ,
where oA are the fine points of A in P(n) and cA are the coarse points of A in
P(m) .
DEFINITION 2.3
A point x of X=P(low)=P(m) or of oX=P(high)=P(n)
is a limit point of a subset
A of Y= P(low)+P(high) (and oA is a subset of oX) , iff there is a positive seemingly
infinitesimal de of P(high) such that
for any positive seemingly infinitesimal da of P(high) less that de ,
there is a fine point y of oA such that |x-y|=da. We denote the set of fine points
of P(high) limit points of A by oL(A) and all coarse points of P(low)=P(m) by
L(A). We define as closure cl(A) of a subset A of Y , the cl(A)=A union Cl(A). A
set is open if its complement in Y is the closure of a set.
Notice
that with the closure we add only coarse visible points not fine (possibly
invisible) points. For this reason the closure operator has the idempotent
low Cl(Cl(A))=Cl(A). For the relations of limit points, closure, boundary,
open sets etc see [9] J. Munkress. In addition Cl(A union B)= Cl(A) union Cl(B)
and Cl(A intersection B) =Cl(A) intersection Cl(B). We define that a x point of
Y is seemingly in contact with the subset A of Y iff x belongs to A union Cl(A). In other
words either it belongs to the set or it is a limit point of it.
The
concepts of boundary points and interior points are defined so as
to have the usual properties as well as the concept of open set, base of open sets and base of neighbourhoods
in Y. Similarly for connectedness. (See
e.g. [9] J.Munkres)
The
concept of topological lowest visible or
accountable or computable compactness is defined in the usual way , where
far the existence of finite sub-cover for any cover, we require , existence of lowest visibly finite cardinality of a sub
cover. Similarly for the concept of lower
visible or computable or accountable compactness or simply visibly compactness of a set of
points. For a first outline of the Digital
Calculus we will not proceed in these details.
The basic properties of continuity are:
1)
Continuity is invariant
by linear combinations
2)
Continuity and product
3)
Continuity and quotient
4)
Composition of digital
continuous functions are digital continuous
5)
Bolzano theorem (after
the supremum property of digital real numbers)
6)
Mean value theorem.
PROPOSITION 2.1 (CONTINUOUS
COMPOSITE)
Let
two digital functions f:[α,β]m->R(m,n) , with oof: [α,β]p->P(p)
, of=[oof]n , f=[of]m and h:[f(a),f(b)]m->R(m,n) , with ooh: [f(a),f(b)]p->P(p) ,
oh=[ooh]n , h=[oh] , that the
first is (digitally) P(m)/P(n)/P(p) continuous and the second P(m)/P(p)/P(q) continuous such that their composition f(h)(x): [α,β]m->R(m,n)
defined by oor=[oof(ooh([x]p ))]m (and or ,r defined in the obvious way), is also a digital function with values in P(m) (in other words
its diagram commutes) . Then this
composition function is also a (digitally) P(m)/P(n)/P(q) continuous function
in [a,b]m.
Hint
for a proof: From the definition of the
composite digital function oor on x of [a,b]p
if dx is a seemingly infinitesimal at x of
P(p) , then from the P(m)/P(n)/P(p) continuity of ooh at x we get that the dy=nooh(dx) is a seemingly infinitesimal of P(n) relative
to P(m) , and from the P(m)/P(n) continuity of the of we get that the of(dy) is
a seemingly infinitesimal of P(n) , relative to
P(m). Thus the composite r is digitally P(m)/P(p) continuous. QED
PROPOSITION
2.2 (CONTINUOUS LINEAR COMBINATIONS)
Let two digital functions f:[a,b]m->R(m,n)
, with of: [a,b]n->P(n) , f=[of]
, and h:[a,b]m->R(m,n) , with oh: [a,b]n->P(n)
, h=[oh] , that are (digitally) P(m)/P(p)/P(q) continuous such that for any
digital scalars a, b of P(m), the
functions af+bh, f*h, 1/f are also digital functions on [a,b]m with
values in P(m), then they are also (digitally) P(m)/P(n)/P(q) continuous
functions.
Hint
for a proof: From the P(m)/P(p)/P(q) continuity of the f and h we get that for
dx seemingly infinitesimals of P(q), the df(x), dh(x) are seemingly
infinitesimals of P(p) and from the ideal-like property of the P(p) seemingly
infinitesimals (see definition of digital real numbers 10) ) the adf(x)+bdh(x)
is a seemingly infinitesimal of P(n) relative to P(m), thus the linear combination
is P(m)/P(n)/P(q) digital continuous . QED
PROPOSITION
2.3 (CONTINUOUS PRODUCT)
Let two digital functions f:[a,b]m->R(m,n)
, with of: [a,b]n->P(n) , f=[of]
, and h:[a,b]m->R(m,n) , with oh: [a,b]n->P(n)
, h=[oh] , that are (digitally) P(m)/P(p)/P(q) continuous such that for any
digital scalars a, b of P(m), the
functions f*h, is also digital functions on [a,b]m
with values in P(m), then they are also (digitally) P(m)/P(n)/P(q) continuous
functions.
Hint
for a proof: From the P(m)/P(p)/P(q) continuity
of the f and h we get that for dx seemingly infinitesimals of P(q), the df(x),
dh(x) are seemingly infinitesimals of P(p) and from the ideal-like property of
the P(p) seemingly infinitesimals (see definition of digital real numbers 10) )
the df(x)*dh(x) is a seemingly infinitesimal of P(q) relative to P(m). Then the
df(x)h(x) =pf(x+dx)h(x+dx)-f(x)h(x)=p (f(x)+df(x))(h(x)+dh(x))-f(x)h(x)=p
by multiplying out we get a linear combination of seemingly
infinitesimals of P(p) and P(q) that by the ideal-like property of the
seemingly infinitesimals are also seemingly infinitesimals of P(n) relative to
P(m) . Thus the product is P(m)/P(n)/P(q) digital continuous. QED
PROPOSITION
2.4 (CONTINUOUS INVERSE)
Let a digital functions f:[a,b]m->R(m,n)
, with of: [a,b]n->P(n) , f=[of]
, that is (digitally) P(m)/P(p)/P(q) continuous such that
the functions 1/f is also definable digital functions on [a,b]m with
values in P(m), then it is also
(digitally) P(m)/P(n)/P(q) continuous function.
Hint
for a proof: From the P(m)/P(p)/P(q) continuity
of the f we get that for dx seemingly infinitesimals of P(q), the df(x), is
seemingly infinitesimals of P(p). The d(1/f(x)) =p(f(x+dx)-f(x))/f(x)*(f(x+dx)=p
(df(x))/f(x)*(df(x)+f(x)). The denominator is a computable finite number and
non-seemingly infinitesimal of P(m), while the numerator is a seemingly
infinitesimals of P(p). From the
ideal-like properties of the seemingly infinitesimals we deduce that the ratio
is a seemingly infinitesimal of P(n). Thus
the inverse is P(m)/P(n)/P(q) digital
continuous. QED
PROPOSITION
2.5 (BOLZANO)
Let a digital (digitally) continuous functions f:[a,b]m->R(m,n)
, with of: [a,b]n->P(n) , f=[of]
f:P(m)->P(m), defined in a finite interval [a,b]m of P(m) such
that , f(a), f(b) have opposite signs, that is f(a)f(b)<m0, (e.g.
assume f(a)<=m0 ) then there is at least one point c in the open
interval (a,b)m, such that for its next higher point c’ in [a,b]m
holds f(c)<=m0 and f(c’)>=m0
Hint
for a proof: We apply the supremum completeness property for upper bounded sets of
the digital real numbers at the P(m) precision level for the set A={x/ a<=mx<=b that the f is negative in the [a,x] }. QED
PROPOSITION
2.6 (MAXIMUM)
Let a digital (digitally) continuous functions f:[a,b]m->R(m,n)
, with of: [a,b]n->P(n) , f=[of]
f:P(m)->P(m), defined in a finite interval [a,b]m of P(m)
, then it attains its maximum in [a,b]m, in other words there is a
number y in [a,b]m in P(m), such that f(x)<=mf(y) for
all x in [a,b]m in P(m).
Hint
for a proof: We apply the supremum property of the
digital real numbers at the P(m) precision level for the set A=f([a,b]) in P(m) . As A is a finite set it
has a maximum element.
DEFINITION
2.3
A digital real function defined on a closed interval f
:[a,b]m ->P(m), of: :[a,b]n ->P(n), is (digitally) is P(m)/P(n)/P(n) differentiable
at a point a of its domain of definition [a,b]m in P(m)
, if for every other point x’ of its domain of definition [a,b]n
in P(n) , such that the distance of a and x’
is seemingly infinitesimal belonging in P(n)
and relative to P(m)) with dx=n x’-a, then dy=nf(x’)-f(a)is
a seemingly infinitesimal relative to P(m) , belonging to P(n) and the
ratio dy/dx=m(f(x’)-f(a))/(x’-a) is always
the same as number c of P(m) , independent
from the choice of x’ which is called the derivative of f at a ,c=m
df(x)/dx|a , while
the c- dy/dx=n c-(f(x’)-f(a))/(x’-a) is a seemingly infinitesimal
relative to P(m) and belonging to P(n).
Notice that when change seemingly
infinitesimals dx, the dy/dx may change as number of P(n) ,but remains constant
as number of P(m).
Similarly
we may define differentiation by the pairs of precision levels P(m)-P(p), and
P(m)-P(q).
DEFINITION
2.4
A digital real function defined on a closed interval f
:[a,b]m ->P(m), of: :[a,b]n ->P(n), is (digitally) is P(m)/P(n)/P(p) differentiable
at a point a of its domain of definition [a,b]m in P(m)
, if for every other point x’ of its domain of definition [a,b]n
in P(n) , such that the distance of a and x’
is seemingly infinitesimal (that is in P(p)
and relative to P(n) and P(m)) with dx=n x’-a, then dy=nf(x’)-f(a)is
a seemingly infinitesimal relative to P(m) , belonging
to P(p) and the ratio dy/dx=m(f(x’)-f(a))/(x’-a)
is
always the same as number c of P(m) , independent from the choice of x’ which is called the
derivative of f at a ,c=m df(x)/dx|a , while the c- dy/dx=p c-(f(x’)-f(a))/(x’-a)
is a seemingly infinitesimal relative to P(m) and belonging to P(n).
Notice that when change seemingly
infinitesimals dx, the dy/dx may change as number of P(n) ,but remains constant
as number of P(m).
Similarly
we may define differentiation by the pairs of precision levels P(m)-P(p), and
P(m)-P(q).
The basic properties of differentiability
are
1)
Chain Rule
2)
Linearity
3)
Product or Leibniz rule
4)
Quotient rule
PROPOSITION 2.7 (CHAIN
RULE)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[f(a),f(b)]m->R(m,n) , with oh: :[f(a),f(b)]n ->P(n)
, h=[oh] , that are the first (digitally) P(m)/P(n)/P(p)
differentiable at a(in P(m)) and the
second P(m)/P(p)/P(q)
differentiable at f(a) in P(m) such that
their composition f(h)(x): [a,b]m->R(m,n) defined by
oor=[oof(ooh([x]p ))]m (and
or ,r defined in the obvious way),is also a digital function with values in P(m) (in other words
its diagram commutes), and the product (df/dx)*(dh/dx) exists in P(m) too. Then their composition function is also a
(digitally) P(m)/P(n)//P(q) differentiable function at a and
Or
in other symbols if df(a)=db, df(h(a))=dγ,
da=dx|a
Hint for a proof: We
start with a seemingly infinitesimal dx of
P(q) relative to P(p), then from the P(m)/P(n)/P(p) differentiability of
h, the dh(x) is a seemingly infinitesimal of P(p), relative to P(n) and the
derivative dh(x)/dx exists in P(m). Taking this dh(x) seemingly infinitesimal
of P(n) relative to P(m) , from the P(m)/P(n)/P(p) differentiability of f, the
df(h(x))/dh(x) exists as element of P(m) and thus by multiplying
(df(h(x))/dh(x))* dh(x)/dx=m
df(h(x)/dx,
the quotient by the hypotheses exists in P(m) therefore the composite is
P(m)/P(n)/P(q) differentiable and the chain rule holds. QED
PROPOSITION 2.8 (Linear
combination)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(p)/P(q) differentiable at a point x such that their linear combination adf(x)/dx+bdh(x)/dx
for constants a, b of P(m),is again
inside P(m). Then their linear
combination af(x)+bh(x) function at x is also a (digitally) P(m)/P(n)/P(q) differentiable
function and
Hint for a proof: If
dx is a seemingly infinitesimal of P(q) relative to P(p), then it holds that
The
d(af(x)+bh(x)=n adf(x)+bdh(x)
is seemingly infinitesimal of P(p) relative to P(n). Thus from the
P(m)/P(p)/P(q) differentiability of the f and h, the d(af(x)+bh(x))/dx=m adf(x)/dx+bdh(x)/dx is by hypotheses in P(m) too, and the
property holds. QED
PROPOSITION 2.9 (Leibniz
product rule)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(p)/P(q)
differentiable at a point x such
that the expression (df(x)/dx)*h(x)+f(x)*(dh(x)/dx) is
again inside P(m). Then the product
f(x)*h(x) function at x is also a
(digitally) P(m)/P(n)/P(p) differentiable function and
Hint for a proof: If
dx is a seemingly infinitesimal of P(q) relative to P(p), then d(f(x)*h(x))=p(f(x+dx)h(x+dx)-f(x)h(x))=p((f(x)+df)(h(x)+dh)-f(x)h(x))=p(fdf+hdf+dfdh)
and by the ideal-like property of the infinitesimals it is in P(p). Thus
d(f(x)h(x))/dx=mf(dh(x)/dx)+h(df(x)/dx)+ df*(dh(x)/dx). The last
terms is zero in P(m) because the df is seemingly infinitesimal relative to
P(m),and the sum of the first two terms exists in P(m) by the hypotheses, thus
the product is P(m)/P(n)/P(q) differentiable and the Leibniz product rule
holds. QED
PROPOSITION 2.8
(Quotient)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , and h:[a,b]m->R(m,n) , with oh: :[a,b]n
->P(n) , h=[oh] , that are
(digitally) P(m)/P(p)/P(q) differentiable
at a point x such that their quotient f(x)/h(x) is defiable and inP(m) and the
right hand of the formula below is computably finite , that is it belongs to
P(m) when the terms of do. Then the quotient f(x)/h(x) function at x is also a (digitally) P(m)/P(n)/P(p) differentiable function and
Hint
for a proof: Similar, as in the product rule. It
is based on the ideal-like properties of the seemingly infinitesimals, and the
hypotheses of the theorem. We start with a seemingly infinitesimal of P(q)
relative to P(p), and calculate the d(f/h). We substitute the f(x+dx) , h(x+dx)
with f(x)+df , h(x)+dh in P(p) , make
the operations , we use the P(m)/P(p)/P(q) differentiability of the f and h,
and that the right hand side of the formula in the theorem, also belongs to
P(m) and we get the P(m)/P(n)/P(q) differentiability of the quotient. QED
PROPOSITION 2.10 (Continuity
of differentiable function)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , which is (digitally) P(m)/P(n)/P(p) differentiable at a point a of
P(m). Then it holds that it is also a (digitally) P(m)/P(n)/P(p) continuous
function at a.
Hint for a proof: From
f(x)’=m df(x)/dx in P(m) and a seemingly infinitesimal dx
of P(p) we get that df=n f(x)’*dx
. And from the ideal-like properties of the seemingly infinitesimals, the right
hand side is also in P(n) and seemingly infinitesimal. Thus the f by the
definition of continuity is P(m)/P(n)/P(p) digitally continuous. QED
DEFINITION 2.4
(Higher dimension total
derivative of a digital k-vector function.)
Let
Am closed rectangle subset of Pk(m) and let a digital
vector function f:Am->Ps(m),
of: An ->Ps(n)
,f=[of]m .We define that f is (digitally) P(m)/P(n)/P(p) differentiable
at a point a in Am iff there
is a linear transformation L: Pk(m)->Ps(m),
such that for any seemingly infinitesimal vector dh of Pk(p)
relative to Pk(m) , it holds
that
in P(m)
The linear transformation
L is denoted by D(f(a)) and is called total derivative of f at a.
It
can be proved that any such linear transformation L if it exists it is unique.
This
is somehow equivalent to that
1)
For every seemingly
infinitesimal dh of P(p)^k at a point a of P(m), dhf(a)=mL(dh)
2)
And also for this seemingly
infinitesimal dh , the dhf(a)-L(dh) as seemingly infinitesimal of
P(n)^k is transcendentally smaller than the seemingly infinitesimal dh of P(p)^k
.
L
is can be a function of P(n) not only of P(m) that is definable in seemingly
infinitesimals too.
Properties of classical total derivative
are:
1)
Partial derivatives per
coordinate exist and their Jacobean matric is the matrix of the total
derivative (differential)
2)
Conversely if they exist
and are continuous in a region then the total derivative exist, and the digital
vector function is called continuously differentiable.
3.
THE
DEFINITION OF THE DIGITAL ARCHIMEDEAN MEASURE AND INTEGRAL.
At first we define the digital Archimedean
Integral and then also the Archimedean measure, although it can be vice versa.
DEFINITION
3.1
Let a subset A of a closed interval [a,b]n of P(n) , with [a,b]m belonging to
P(m), of cardinal number of points |A| which
is a number of P(n) and in general seemingly infinite relative to P(m) . We
define as Archimedean measure of A, in symbols m(A) , and call A , P(m)/P(n)-countably
measurable, or simply P(m)/P(n)-measurable,
a possibly of seemingly infinite terms relative to P(m) sum of |A| times
of the P(n)-sizes of the points of A, such that the P(m) rounding of the sum belongs
to P(m). In other words as each point of A in P(n) has size 10-n then m(A)=[|A|*10-n ]m which is a number required to belonging to
P(m) for A to be P(m)/P(n)-measurable.
Similar
definition exists for higher dimensions Rk(m,n,p,q)
DEFINITION
3.2
Let
a digital functions f:[a,b]m->P(m) , with of: [a,b]n->P(n)
, f=[of] . Then we define as Archimedean P(m)/P(n)-integral of f on the closed
interval [a,b]m , and call
the f Archimedean P(m)/P(n)-integrable, the possibly of seemingly infinite terms
relative to P(m) sum of |[a,b]n|
times of the P(n)-sizes of the points dx of [a,b]n multiplied with the value of(x) at each point
dx of [a,b]n ,such that the P(m) rounding of this weighted sum belongs to P(m). In symbols
in P(m)
Notice
that according to that definition the Archimedean measure of a subset A of
[a,b]m is the Archimedean of
the characteristic function XA of
A. In symbols
is
in P(m)
Similar
definition exists for higher dimensions Rk(m,n,p,q)
Similarly we may define measure and integration by the pairs of precision levels P(m)-P(p),
and P(m)-P(q) etc.
The basic properties of the classical
Integral are:
1) Continuous=>
Integrable
2) Linearity
3) Inequality
4) Additivity
at the limits of integration
5) Upper,
Lower bounds and the limits of integration
6) Absolute
value inequality
7) Additive
property of point measure
m(AᴗB)=m m(A)+m(B)-m(AᴖB)
8) It
holds also that functions that differ only at a set of measure zero have the integrals.
PROPOSITION 3.1(Measure
zero)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(n) integrable on [a,b]m , such
that they differ in values only on a subset of [a,b]m of
(Archimedean) measure zero , then their (Archimedean) integrals are equal.
Hint for a proof: It
suffices to prove that the Integral of their deference is zero. Which is
point-wise zero at all points of [a,b]n in P(n), except at the
points of a subset A of the closed interval of measure zero, m(A)=m0
. Since the A is a finite set, the f(A) has a maximum M in P(m) , which when
factored out in the finite sum which is the Archimedean P(m)/P(n) integral, it will give an upper bound for the
integral of the f(x)-h(x) , of the type M*m(A). But as m(A)=0, then the
integral of f(x)-h(x) is lso zero in P(m) QED.
PROPOSITION 3.2 (Continuity
implies intergarbility)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , which is (digitally) P(m)/P(n)/P(p) continuous in the closed
interval [a,b]. Then it holds that it is
also a (digitally) P(m)/P(p) integrable
function at [a,b]m and
is in P(m)
Hint for a proof: Since
the f(x) is continuous on [a,b] by proposition 2.6, it has a maximum M. As in
the proof of the previous proposition when M is factored out in the finite sum
which is the Archimedean P(m)/P(n)
integral, it will give an upper bound for the integral of the f(x) , of
the type M*|b-a| . Therefore the integral sum is upper bounded in P(m) and it
exists therefore as a number of P(m). Thus if(x) is P(m)/P(n) integrable QED.
PROPOSITION 3.3 (Additive
decomposition of interval)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , which is (digitally) P(m)/P(n) integrable on the closed
interval [a,b]m. Then for an
c of [a,b]m in P(m) it holds that f
it is also a (digitally) P(m)/P(n) integrable function on [a,c]m and [c,b]m
and
Hint for a proof: Direct
consequence from the associative property of finite sums in P(n). QED
PROPOSITION 3.4 (Linear
combination)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(n) integrable on [a,b]m , such
that their linear combination kf(x)+lh(x) for constants k, l of P(m),is again
inside P(m). Then their linear combination kf(x)+lh(x) function is also (digitally)
P(m)/P(n) integrable digital function on [a,b]m and
Hint for a proof: Direct
consequence from the associative and distributive law, of finite sums in P(n).QED.
PROPOSITION 3.5 (Upper,
Lower bounds inequalities)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , which is (digitally) P(m)/P(n) integrable on the closed
interval [a,b]m ,such
that for constants m, M of P(m), it
holds that m<=mf(x)<=m M . Then
m*(b-a)<=m
<=m
M(b-a).
Hint for a proof: Direct
consequence from the distributive law and corresponding inequalities of finite
sums. QED.
PROPOSITION 3.6 (Integrability)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of] , which is upper bounded by a number of P(m): f(x)<=m M and
M and also (b-a)M are in P(m) for all x in P(n). Then it is Archimedean P(m_)/P(n)
integrable:
I=m
exists as a number of P(m)
Indication for a Proof:
In the definition of the Archimedean integral, in the finite (but seemingly
infinite) sum of terms f(x)dx in P(n) we may substitute f(x) with its bound M ,
and factor out the M, by the distributive law of finite sums, while the sum of
dx’s give the length of the interval [a,b]=m b-a. Therefore the
integral is upper bounded by (b-a)M in P(m) , which means that the rounded in
P(m) sum and Integral exists also in P(m), thus the function is Archimedean
integrable.
PROPOSITION 3.7 (Inequality
with absolute values)
Let
a digital functions f:[a,b]m->R(m,n) , with of: [a,b]m->P(n)
, f=[of]
f:[a,b]n->P(m),
which is integrable on [a,b]m .Then it holds that |f| is also
integrable on [a,b]m and
Hint for a proof: Direct
consequence from the corresponding same
inequality property of absolute values for finite sums in P(n). QED
PROPOSITION 3.8 (Integration
by parts)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(p) integrable on [a,b]m , such that the next integrals on [a,b]m exist
,
then
Where the derivatives are P(m)/P(n)/P(p)
differentiation.
Hint
for a proof: Remember that here the seemingly infinitesimals
dx are real finite numbers of P(p). By cancelling out the dx in the integrals
in the left side, and substituting the df(x) , dh(x) , with their equals in P(p), f(x+dx)-f(x) ,
h(x+dx)-h(x) , we multiply out them so that these terms as terms of successive
finite differences in the finite sum, which is the integral cancel out, to give
the right hand side. QED.
PROPOSITION 3.9 (Inequality 2)
Let
two digital functions f:[a,b]m->R(m,n) , with of: [a,b]n->P(n)
, f=[of]
,
and h:[a,b]m->R(m,n) , with oh: :[a,b]n ->P(n) ,
h=[oh] , that are (digitally) P(m)/P(n) integrable on [a,b]m and f(x)<=n h(x) in [a,b]n
then it holds that
Hint for a proof:
Direct consequence from the corresponding similar property of finite sums, which
is the integral here. QED.
PROPOSITION 3.10 (Additivity of Archimedean measure )
Let
a sets A, B, in P(n) that are Archimedean measurable. Then also their union AᴗB
and their intersection AᴖB are
Archimedean measurable and it holds for their Archimedean measure symbolized by
m(), that
m(AᴗB)=m m(A)+m(B)-m(AᴖB).
Hint for a proof: Direct
consequence from the corresponding same formula of cardinality of finite sets,
and the definition of the Archemidean P(m)/P(n) measure of a set as finite sum
of that of its points. QED.
Fubini Theorem It
can be deduced as in classical Calculus that we can get the value of the
integral by iterative one dimensional integrals once the lower or upper one-dimensional integrals exist. It is the results
Associative and commutative property of finite sums.
PROPOSITION 3. 12 (Fubini
theorem iterated integrals)
Let
A closed rectangle subset of Pk(m)
and Bm closed rectangle subset of Ps(m) and let
digital function f:AxB ->P(m),
of: AxB ->P(n) ,f=[of] (digitally) integrable.
For
x in A let hx : B->P(m) be
defined by hx(y)=mf(x,y) , and we assume that it is also
a digital function and let
which
is assumed also a digital function.
Then
I(x) is (digitally) integrable on A and
it holds that
Hint for a proof: Direct
consequence of the associative and distributive property of the finite sums.
QED
4.
THE
FUNDAMENTAL THEOREM OF THE DIGITAL CALCULUS AS THE RELATION OF THE DIGITAL
DERIVATIVE WITH THE DIGTAL INTEGRAL.
It is simply the formal expression that a
weighted sum that is the mass of segment
when getting its derivative to length it will give the linear density of the
segment, which is also a derivative.
PROPOSITION 4.1 (FUNADMENTAL THEOREM OF CALCULUS)
Let
a digital functions f:[a,b]m->P(m) , with f=[of]
f:[,ab]n->P(n),
which is
(digitally) P(m)/P(n)/P(p) continuous thus P(m)/P(p) integrable on the closed
interval [a,b]m and also the
next function on [a,b]n is a
digital function.
Then
it holds that the function at [a,b]m
is (digitally)
P(m)/P(n)/P(p) differentiable and at any
c of [a,b]m .
Hint
for a proof: For a seemingly infinitesimal dx of
P(p) relative to P(n) the dh(x)=nh(x+dx)-h(x). But by the proposition 3.3 of additive
decomposition of the integral over its intervals of integration gives
h(x+dx)-h(x)=nh(x)+f(x)dx-h(x), thus dh(x)=nf(x)dx. And
by the ideal-like properties of the seemingly infinitesimals it is also a
seemingly infinitesimal of P(n). Thus the h is P(m)/P(n)/P(p) differentiable
with derivative equal to f(x) in P(m). QED.
5.
CONCLUSIONS
AND PERSPECTIVES.
For all practical reasons in the physical
and social sciences the digital calculus gives all the well-known applications
with a finite ontology which is directly realizable both in the physical
ontology of atomic matter or digital ontology of operating systems of
computers. This has vast advantages in applications in, Engineering, Physics, Meteorology,
Chemistry, Ecology, social sciences etc.
The digital Calculus also resurrects the
17th and 18th century mathematical arguments in Calculus
and mathematical physics that treated the “infinitesimals” as separate entities
in the derivatives.
The digital Calculus is also an
educational revolution in the Education of Mathematics. . It is a new method of
teaching mathematics where there is higher integrity with what we say, write,
see, and think.
After [8] that defines the axiomatic
Euclidean geometry and the current outline of the digital Differential and
Integral Calculus, one may define and solve the digital differential and
partial differential equations as essentially difference equations, (with
easier applications in the physical sciences), digital fluid dynamics (with
easier applications in physics), digital differential geometry, digital
functional analysis (appropriate for easier applications in signal theory) etc.
The road is open and the digital world of the computers is the direct tool for
this.
REFERENCES
[1] APOSTOL T. 1974
“Mathematical Analysis” 2nd
edition Addison Wesley Publishing Company. 1974
[2] Banach-Tarski paradox:
[ 3] Boltianskii V.
(1978)“Hilbert’s 3rd problem” J. Wesley & Sons 1978
[5] Wilson, Trevor M. (September 2005). "A continuous
movement version of the Banach–Tarski paradox: A solution to De Groot's
problem". Journal of Symbolic Logic. 70 (3):
946–952. JSTOR 27588401. doi:10.2178/jsl/1122038921.
[6]
EVANS L. C. (2010) Partial Differential Equations 2nd edition, Graduate Texts in
Mathematics, American mathematic Society, Providence Rhode Island
[7] Hausdorf paradox:
[8] Kyritsis K. An
Axiomatic System for a Physical or Digital but Continuous 3-Dimensional
Euclidean Geometry, Without Infinite Many Points. World Journal of Research and Review (WJRR) ISSN:2455-3956, Volume-5,
Issue-4, October 2017 Pages 31-43
[9] Munkres J. R.
Topology (a first course)
editions Prentice Hall
[10] Von Neumann paradox:
[11] RUDIN,
W. 1976 “Principles of Mathematical Analysis ”3rd edition McGraw-Hill Inc. 1976
[12] E. Schroedinger. Science
and Humanism Cambridge University press 1961
[13]
SPIVAK, M. 1965 “Calculus on Manifolds” The Benjamin/Cumming publishing company 1965.
[14]
SPIVAK, M. 1967 Calculus The
Benjamin/Cumming publishing company 1967.
[15] VAN DER WAERDEN ALGEBRA
Vol I, II Springer 1970