ENTROPY & INFORMATION a physicist point of view Jean V. Bellissard Georgia Institute of Technology & Institut Universitaire de France
Dec 25, 2015
ENTROPY & INFORMATION
a physicist point of view
Jean V. Bellissard
Georgia Institute of Technology
& Institut Universitaire de France
ENTROPY:
Some history
Carnot’s Principle:
• Sadi CARNOT• 1825: • Reflexions sur la Puissance
Motrice du Feu
Carnot’s Principle:
• Sadi CARNOT• 1825: • Reflexions sur la Puissance
Motrice du Feu
A steam machine needs 2sources of heat:
- a hot one: temperature Th
- a cold one: temperature Tc
Th > Tc
Carnot’s Principle:
• Sadi CARNOT• 1825: • Reflexions sur la
Puissance Motrice du Feu
The proportion of thermalenergy that can betransformed into mechanicalmotion depends only on thetemperatures of the twosources
Steam Engines
• Any steam engine has
a heat source (burner)
and a cold source
(the atmosphere).
Thermal engines are everywhere
- in power plants (coal, nuclear, …)- in cars, airplane, boats,- in factories,
Entropy: definition
• Rudolf CLAUSIUS• 1865:
Definition of entropy: S = Q/T
• 2nd Law of Thermodynamics:
Entropy cannot decrease
over time
Gas are made of molecules
• Clausius showed that gas were made of molecules, explaining the slow diffusion of dust and the origin of viscosity
QuickTime™ and aGIF decompressorare needed to see this picture.
Statistical Thermodynamics:
• Ludwig BOLTZMAN• 1872:- Kinetic theory
• 1880:Statistical interpretation of entropy:disorder in energy space
Statistical Mechanics
• Josiah Willard GIBBS
• 1880’s:
Thermodynamical equilibrium corresponds to maximum of entropy
• 1902 : book
« Statistical Mechanics »
Information theory
• Claude E. SHANNON
• 1948:
« A Mathematical Theory
of Communication »
-Information theory
-Entropy measures the
lack of information of a
system
Second Law of Thermodynamics
• Over time, the information contained in an isolated system can only be
destroyed• Equivalently, the entropy can only
increase
MORPHOGENESIS:
how does nature produces information ?
Conservation Laws
• In an isolated system, the Energy, the Momentum, the Angular Momentum, the Electric Charge,…. are conserved.
Conservation Laws
Angular momentum
Conservation Laws
• At equilibrium, the only information available on the system are the values of conserved quantities!
• Example: elementary particles are characterized by their mass (energy), spin (angular momentum), electric charge…
• Electron : m = 9.109x10-31 kg, s = 1/2, e = —1.602 x10-
19 C,
Out of Equilibrium
• Variations in time or space force transfer of conserved quantities
• Transfer of Energy (Heat), Mass, Angular Momentum, Charges, creates current flows.
E E’
time
flow
• Transfer of Energy (Heat), creates heat current like in flames and fires.
Out of Equilibrium
• Transfer of Mass, creates fluid currents like in rivers or streams.
Out of Equilibrium
• Transfer of Charges, creates electric currents.
Out of Equilibrium
• Transfer of Angular Momentum creates vortices like this hurricane seen from a satellite.
Out of Equilibrium
• Pattern Formation
A shallow horizontal liquid heated from below exhibits instabilities and formation of rolls and patterns, as a consequence of fluids equations
Out of Equilibrium
Explosions produceinterstellar clouds
Collapses produces stars
The Sun, the Moon, The Planets, and the Stars have been used as sources ofinformation:measure of time, localization on Earth
Out of Equilibrium
Beating the 2nd Principle
• Without variations in time and space the only information contained in an isolated system is provided by conservation laws
• Motion and heterogeneities allow Nature to create a large quantity of information.
• All macroscopic equations (fluids, flame,…) describing it are given by conservation laws
CODING INFORMATION
the art of symbols
Signs• Signs can be visual
color, shape, design
Signs• Signs can be a sound
ring, noise, applause musical, speech
Signs• Signs can be a smell
Signs• Signs can be a smell
Signs• Signs can be a smell
plants can warn their neighbors with phenols
Signs• Signs can be a smell
female insects can attract males with pheromones
Writings
Writings• More than 80,000
characters are used to code the Chinese language
Writings• Ancient Egyptians used
hieroglyphs to code sounds and words
Writings
• Japanese language is also using the 96 Hiragana character coding syllables
Writings• the Phoenicians and
the Greeks found the alphabet simpler to code elementary sounds with 23 characters
Writings• Modern numbers are
coded with 10 digits created by Indians and transmitted to Europeans through the Arabs
Writings• George BOOLE (1815-
1864)
used only two characters to code logical operations
0 1
Writings• John von NEUMANN
(1903-1957)
developed the concept of programming using also binary system to code
all possible information
0 1
Writings
• Nature uses 4 molecules
Writings
• Nature uses 4 molecules to code
Writings• Nature uses 4
molecules to code the genetic heredity
Writings• Proteins uses 20
amino acids to code their functions in the cell
molecule of Tryptophan, one of the 20 amino acids
Unit of information
• Following Shannon (1948) the unit is the
bit A system contains N-bits of information
if it contains 2N possible characters
TRANSMITTING INFORMATION
redundancy
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 coding
1
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 000 coding
1 111
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 000 coding
1 111
Transmission
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 000 coding
1 111
Transmission
errors(2nd Principle)
010
110
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 000 coding
1 111
Transmission
errors(2nd Principle)
010
110
Reconstruction
Transmitting• Coding theory uses
redundancy to transmit binary bits of information
0 000 coding
1 111
Transmission
errors(2nd Principle)
010
110
Reconstruction
at reception (correction)
000
111
Transmitting• Humans use also
redundancy to make sure they receive the correct information
Transmitting• Humans use also
redundancy to make sure they receive the correct information
Transmitting• Humans use also
redundancy to make sure they receive the correct information
say it again !
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
Transmitting• Prior to the cell fission
the DNA molecule is unzipped
Transmitting• Prior to the cell fission
the DNA molecule is unzipped by another protein
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
QuickTime™ and aGIF decompressorare needed to see this picture.
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Transmitting• A cell is a big factory
designed to duplicate the information contained in the DNA
mitosis
Beating the 2nd Principle
• The cell divides before the information contained in the DNA fades away
• In this way, cell division and DNA duplication at fast pace, conserve the genetic information for millions of years.
THE MAXIMUM ENTROPYPRINCIPLE REVISITED
The scary art of extrapolation
Equilibrium• A physical system of
particle reaches equilibrium when all information but the one that must be conserved have vanished
Equilibrium• A physical system of
particle reaches equilibrium when all information but the one that must be conserved have vanished
In a gas the chaotic motion produced by collisions is responsible for the loss of information
Equilibrium• By analogy other systems
involving a large number of similar individuals can be treated through statistics and information
Equilibrium• By analogy other systems
involving a large number of similar individuals can be treated through statistics and information
Like bureaucracy
Equilibrium• By analogy other systems
involving a large number of similar individuals can be treated through statistics and information
Like bureaucracy
1837 J. S. MILL in Westm. Rev. XXVIII. 71 That vast net-work of administrative tyranny…that system of bureaucracy, which leaves no free agent in all France, except the man at Paris who pulls the wires.
(Oxford English Dictionary)
Bureaucracy• China (3rd century BC)
Confucius• France (18th century)• USSR (1917-1990)• European Community
(1952)
The French ENA:National School of Administration
Bureaucracy
Bureaucracy• Rules Conserved
quantities
Bureaucracy• Rules Conserved
quantities• Individuals particles
undiscernable
Bureaucracy• Rules Conserved
quantities• Individuals particles
undiscernable • Removal Shocks of an individual
Loss of information
Bureaucracy• Rules Conserved
quantities• Individuals particles
undiscernable • Removal Shocks
Loss of information
Maximum of entropy
No evolution
Bureaucracy
• A bureaucratic system is stable (its entropy is maximum).
• Example: China empire lasted for 2000 years.
• It cannot be changed without a major source of instability.
• Example: collapse of the USSR
COMPUTERS:
machines and brains
Computers• Alan TURING
(1912-1954)• 1936: • Description of a
computing machine
• Computers execute logical operations
• They produce information, memorize them, treat them,
Computers• A Turing machine is
sequential: operations are time ordered
tape
states
rules
Left-Right
Computers• The von NEUMANN computer
repeatedly performs the following cycle of events
1. fetch an instruction from memory.
2. fetch any data required by the instruction from memory.
3. execute the instruction (process the data).
4. store results in memory.5. go back to step 1. data data &
instructions
CPU
MEMORY
Computers• February 14th 1946
ENIAC
the first computer
Los Alamos NM
Computers• Cellular automata
produce patterns as in shells
a
b b
a
a
b
a
a
b
a
b
a
b
a
rule change patternfrom layer to layer
computer simulation
Computers• Nature has also
produced brains• Brain does not seem to
follow the von Neumann nor Turing schemes
Computers• In brain signals are not
binary but activated by thresholds
• The operations are not performed sequentially
Computers• Brain can learn• It can adapt itself:
plasticity• Brain memory is
associative: it recognizes patterns by comparison with pre-stored ones
TO CONCLUDE
Entropy & Information
• The Second Law of Thermodynamics leads to global loss of information
• Systems out of equilibrium produce information… to the cost of the environment
• Information can be coded, transmitted, memorized, hidden, treated.
• Life is a way of producing information: genetic code, proteins, chemical signals, pattern formation, neurons, brain.
• Machines can produce similar features
Is Nature a big computer ?
THE END