Questions tagged [information]

Add this Tag for questions on information theory applied to physics, especially in the fields of statistical mechanics and thermodynamics, the black hole information paradox, complexity of dynamical and physical systems and questions to do with whether information is conserved by physical systems. Use the tag quantum information if your question is to do with information theoretic concepts applied to quantum states.

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How to derive Shannon Entropy from Clausius Theorem?

I am studying Quantum Information now, and I need to understand the entropy of a quantum system. But before I go there, I need to understand Shannon Entropy which is defined as : $H(X) = -\sum_{i=1}^{...
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6 votes
3 answers
178 views

Could the speed of causality be (significantly) faster than $c$?

The other day my son (13) asked me whether it was possible that light went very slightly slower than our best measured $c$, and at the same time had a very tiny mass, but we aren't able to measure ...
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-2 votes
1 answer
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If we know information existed when life first began on earth, then can’t we surmise that information existed prior to earth life? [closed]

If true, then wouldn’t information have been created when the universe was created? In other words, if information existed from the start of the universe, then it’s possible that information can not ...
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0 votes
1 answer
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Equivalent Formulation of Least Squares Method in Terms of Entropy

I have learned that people in the field of machine learning and statistics often use the least squares method. Is there any alternative formulation of the least squares method using entropy? (It might ...
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0 votes
1 answer
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Calculate the entropy for an arrangement of quantum particles

I am not a physicist, just read some pages of information theory, and wondered how far off this idea is: Imagine 2 levels and 3 particles that can be distributed in those levels. Also, each state-...
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3 votes
1 answer
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Does information disappear when a wavefunction collapses?

The wavefunction of a particle evolves with time in a manner strictly defined by the Schrodinger equation and the local environment. The wavefunction can become very complicated (e.g. a photon trapped ...
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Does "Superluminal travel of non-information" means we already "achieved" superluminal speeds?

From what I understood of Vsauce video talking about "Superluminal travel of non-information," the absence of information seems to travel faster than the speed of light, since we perceive ...
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Are most reals fake? Does it make a difference?

There are uncountably many reals. However, there are only countably many definable numbers. Thus, almost all reals are undefinable. Undefinable means that the shortest representation of that number ...
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Can the extra information conveyed by the density operator, when we are dealing with fluctuations, be something other than the truth?

Quoting from Amnon Katz's, Principles of statistical mechanics: "Consider a situation in which the energy and the averages of $n$ other quantities $Q_i (i=1,...,n)$ are known: $$\left<H\right&...
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1 vote
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Speed of information related anomaly

Suppose I have a perfectly rigid rod of length $1$ light-year and I am running with that rod with its one end in my hand. I suddenly stop at some moment. Will the other end of the rod continue to move ...
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10 votes
2 answers
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Why can't the information inside a black hole be reconstructed from what's left outside?

In trying to understand the significance of the black hole information paradox: regardless of what happens to information inside a black hole; how come it cannot, in principle, be reconstructed by ...
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Prove that entropy increases with the number of states

According to the formulation of entropy as $$S = -\sum_i P(i)\log(P(i))\quad,$$ how do we know that entropy increases with the number of states of a system regardless of their probability distribution?...
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Entropy and neutral charge

If you have a system $a$ with $N$ particles with charge $+q$ and you put it in contact with a system $b$ that has $N$ particles with charge $-q$, i think the system will evolve to a neutral charged ...
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1 vote
1 answer
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Is there a black-hole information equation?

According to some sources, black-hole information is proportionate to the surface area, and, the equation trotted out is $$S = \frac{A k}{4 l_p^2}.$$ But according to another source, the entropy and ...
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1 vote
1 answer
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Coupled systems and quantum configuration space?

I was watching this PBS Spacetime video. He mentions that quantum particles / wavefunctions (he uses electrons as his example) all have their own set of separate 3D coordinates in a coupled system. ...
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Derive the Gibbs or Shannon entropy from the Boltzmann entropy

Is there a way to derive the Gibbs or Shannon entropy $H = -\sum_p p\ln p$ where $\{p\}$ is the set of probability of all the states in a system, from the Boltzmann entropy $S = \ln\Omega$ where $\...
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Do angular equivalents of linear equations in physics reveal extra information?

First of all, This question is completely based on intuition and some concepts of mathematics. I have been thinking about this now for 5 months and haven't figured it out yet. I am beginner in physics ...
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2 votes
1 answer
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If antiparticles are particles moving back in time, would messages from the future be possible?

So, here's the idea: if Feynman's interpretation of antiparticles is true and antiparticles are particles moving back in time, then they are carrying with them information from the future, no? If that'...
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15 votes
4 answers
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Contradictions caused by moving faster than light

There was a Joe Rogan episode with Brian Greene where Joe thinks aliens are watching us because the universe is infinite and there are an infinite number of them. So some of them must be watching. ...
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1 vote
0 answers
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Information geometry and emerging general relativity in parametric space of univariant Gaussian

I am working on a problem of information geometry. Using Fisher information metric It is possible to show that Einstein tensor and stress energy tensor can be calculated. When I took univariate ...
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0 votes
2 answers
87 views

Formulation of Heisenberg's uncertainty in terms of Shannon entropy

Heisenberg's uncertainty principle $$\Delta x \Delta p \geq h$$ asserts a fundamental limit to the accuracy versus uncertainty with which the values for the two canonically conjugate variables $\Delta ...
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6 votes
2 answers
217 views

What is meant by 2D fourier transform of an image?

I have some questions about this interesting concept I came across about 2D Fourier transform, please... Firstly, the Fourier transform of a 1D signal (such as a sound recording) is as follows: The ...
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The entropy of Hawking Radiation

I am reading the review paper "The Entropy of Hawking radiation" by Almheiri et. al. They show the Page curve in the following figure: However, they do not show a formula of what they refer ...
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0 votes
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A question on Electrical Currents [duplicate]

Veritasium just uploaded this: https://www.youtube.com/watch?v=bHIhgxav9LY I have an issue with the logic behind his answer. his scenario is this: $$\text{...----- Battery-Switch----...}$$ $$\text{...-...
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0 votes
1 answer
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Transport of information in solids [duplicate]

Suppose you have a hypothetical rod long enough to reach Mercury from the Earth. You begin pushing the rod from here in such a manner that the rod reaches mercury in some time. Once the rod reaches ...
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0 votes
1 answer
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When the Earth suddenly stops pulling [closed]

Let's say the Earth stops attracting objects to itself all of a sudden. So, I was wondering what would happen to a person standing on the surface of the Earth? (Neglect the effect of the rotation of ...
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0 votes
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Information travel in the universe

I was wondering how information travels in the universe? I know that information cannot travel faster than the velocity of light, but how exactly does this transfer happen? Like is there any physical ...
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1 vote
0 answers
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Can information leak through between merging black holes during the merger?

There are other questions on this site about black hole mergers and information, but none of them answer my question. What happens to information when black holes merge? This does not give a ...
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0 votes
1 answer
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Earth electromagnetic field

Nowadays an unlimited amount of information can be transferred around the planet using wireless methods. Is that possible to transfer the information using natural electromagnetic field such as Earth ...
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2 answers
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Proof for impossibility of FTL Signals

Is there is formal proof for the fact that signals must always travel at a speed less than the speed of light in a vacuum? I understand that special relativity dictates that for massive particles to ...
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0 votes
1 answer
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Time-orderings for the time-like and light-like vectors cannot be altered

My question concerns the time-ordering for the time-like vector between two space-time points: $$ (t_1,\vec{x_1}) \text{ and } (t_2,\vec{x_2})$$ Is it correct to claim that: For a time-like vector, $(...
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-1 votes
1 answer
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An apparent contradiction in the definition of density matrix

Let $A$ and $B$ be two subsystems of the system AB which is in a pure or isolated bipartite state and $$|\psi_{AB}\rangle=\sum_{i}\sqrt{p_i}|\psi^{i}_{AB}\rangle$$, then by definition \begin{equation} ...
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-1 votes
2 answers
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Informational content of a single symbol

In the communication context, every book i've started to read says: if you want to send a datum about a random experiment $X$, let it be a fair coin toss, that is $$p(tails)=p=0.5; p(heads)=q=0.5$$ ...
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Can Consciousness be Understood as an Emergent Phenomenon of the Evolution of the Human Brain? [closed]

Straight question - is explaining (or at least understanding) consciousness in the realm of physics? Detailed question: We know that consciousness exists. Or rather, I know that I have it. The rest of ...
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0 votes
1 answer
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The second law and the advantage of measurement?

Background To the best of my knowledge, almost all living systems make use of information obtained from sensory organs. If this result is a reflection of natural selection, then this fact suggests ...
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Is it possible to use a distributed camera array to fake an interferometric sensor without phase data?

Astronomical interferometry is a technique which uses multiple small telescopes to mimic one giant telescope. It requires the phase of the light to be captured for it to work. It is widely used in ...
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3 votes
0 answers
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What's wrong with the Maxwell demon? Seems very trivial consequence of the second law of Thermodynamics...?

Maxwell Demon's Paradom: The entropy production of the system $X$ becomes negative: $$\Delta S(X) + Q_X \leq 0$$ Exorcism of the demon: I believe that this paradox has been resolved by an inequalities ...
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1 vote
0 answers
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Chaotic and Ordered Random Boolean Newtorks with a fixed in-degree k and a probability p

I'm working with Random Boolean Networks, I made a python program to show the dynamics of the networks. Before coding the program I study the theory and it says that the in-degree k and the ...
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1 vote
0 answers
50 views

Conservation of information [closed]

Given: The holographic principle as proposed by Susskind that states that the maximum amount of information stored in a 3D volume can be dictated by its surface area. Would not: The simple square-...
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0 votes
1 answer
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Is a correspondence principle valid for physical information?

I could find some physical interpretations of information for quantum systems, but not for classical physics. Can some interpretation of information for macroscopic phenomena given? Say, the ...
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1 answer
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How the information is related to time in physics?

The interpretation of information in physics is confined to assuming instant interactions and stationary states. Today we started to learn that when having higher resolution measurements, even most ...
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2 votes
2 answers
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Can information be analog?

In connection with question What do physicists mean by "information"? I read "information" simply means any particle, feature of in a field (EM, quantum field, curvature in ...
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0 answers
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Why does it matter if information is lost inside a black hole? [duplicate]

What actually happens if information is lost inside black holes? I'm watching a documentary and it said it would destroy our understanding of physics but I don't know why. Even if everything that went ...
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0 votes
1 answer
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Can we deny information theory in Maxwell's demon explanation?

The only problem for the demon is, from outer perspective it seem like entropy inside the box is decreasing. So information theory try to say that missing entropy are converted into information. the ...
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2 votes
1 answer
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Is there a Maximum Data Density of a Physical Volume?

Is there an established or proven relationship concerning how much data can fit in a given volume of space / spacetime?
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1 answer
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What does 'rotating vector addition' mean in this context, and how does it generate AM and FM?

I am currently learning about wave modulation. In communication theory, it is said that 'rotating vector addition' generates AM (amplitude modulation) and FM (frequency modulation). What does '...
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1 vote
2 answers
59 views

Moving a 2x2 the length of the solar system [duplicate]

If we were able to push a 2x2 piece of wood that is the length of our solar system, how would it behave? My colleague says since its all part of the same molecular structure, the whole piece of wood ...
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-2 votes
2 answers
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Can quantum correlations due to measurement be used for quantum communication? [duplicate]

My understanding of quantum entanglement is that when you measure the state of an entangled particle, its counterpart will measure a correlated state, i.e. we know for sure that if for example ...
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1 answer
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Information never gets lost theory - formalization

From a video I say about information theory, the sentence "Information never gets lost, it is there but in different 'arrangement'" Meaning that if we burn a toilet paper into ash, we could ...
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1 vote
1 answer
63 views

Which SI units should I use to describe the length of this question? [duplicate]

I’d like to describe the length of the question text. I’m fairly certain that is not outside the realm of physics, however if I measure it in “bytes” it’s not clear to me how to convert that to SI ...
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