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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Understanding entropy and its connection to probability distributions
Entropy tells us about the "uncertainty" of a probability distribution, i.e. roughly how much information is needed to describe an event that is described by a probability distribution. With ...
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Have we observed any real-like phenomena faster than the speed of light in vacuum? [duplicate]
A common thought experiment about shadows ask, what would happen if a bat flew across a very, very distant star? The farther the star, the faster its shadow would move, and there's no reason it couldn'...
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The source of random information in physics
In computer science, we can use the heat of a gas (or radiation, for example) to generate random noise. From them we can get a lot of random information. However, the question arises, where does this ...
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Quantum entanglement explained by non-local hidden variables when photons are not the propagators of information?
I read in WP that the biggest challenge of non-local hidden variables theory supporters in explaining quantum entanglement is:
Most advocates of the hidden-variables idea believe that experiments ...
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Information processing as a resource
Information processing, whereby we convert or construct a representation of information from other information, has now become an essential component to our current world and the future of our society....
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Is entropy scale-invariant?
The most common definition I’ve heard of entropy in physics is the number of micro-states for a given macro-state. Most examples use the atomic scale as the micro-setting and some kind of simple, ...
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In the Bekenstein bound, is $E$ and/or $R$ meant to be a strict upper bound or an average? (how to fit with position/momentum uncertainty?)
In the Bekenstein bound, $S\le2\pi R E/\hbar c$, where $E$ is the energy of the system (including mass energy etc.), and $R$ is the radius of a ball containing the system, which of these is strict (if ...
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Infinite information in finite volumes of space time?
It recently occurred to me that uncertainty at the quantum level, unintuitive as it may be to our human scale experiences, may solve a fundamental problem: Wouldn't perfect determinism require ...
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Why should the Boltmann distribution maximize entropy with average energy constrained?
In statistical mechanics, when working with the canonical ensemble (e.g. a system able to exchange energy with a large thermostat at temperature $T$, the system together with the thermostat being ...
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Is it possible to transmit information from within a black hole via the momentum of a rocket activated after passing the event horizon?
Imagine a simple, non-rotating black hole and a massive rocket that is free-falling past the event horizon of the black hole, linearly towards the singularity. The rocket is massive enough that it ...
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Does entropy outside of thermodynamics also increase?
Define entropy as $S=-\sum p_{i}\log p_{i}$
This entropy (or some variant of it) appears in many fields such as thermodynamics, chemistry, biology (species diversity), economics (measuring inequality),...
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Prediction and Work
I've had this idea that if you can predict something, you can theoretically extract work from it. For instance if you know a certain mass is going from point A to point B, you can place something in ...
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What is the meaning of divergent quantum fisher information?
I've recently come across this example, and it has me confused. I've computed the quantum fisher information (QFI) for a qubit initialized along the $\hat x$ axis ($|\uparrow_x\rangle=\frac1{\sqrt{2}}\...
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How subjective is entropy really?
I'm a computer scientist doing some research that touches on basic concepts in statistical mechanics: macrostate, microstate and entropy. The way I'm currently conceiving of it is that the microstate ...
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Definition of heat from stat phys [duplicate]
I don't really understand how to couple the idea of entropy as info with heat. Let's say that you have an isolated system. A cube with a a series of movable partitions parallel to a face of the curve. ...
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Imagining Graham's number in your head collapses your head to a black hole
My question is how does the above phenomenon, as mentioned in Numberphile here, occur in a semi-quantitative way through physical laws. (i.e saying statistical mechanics implies that is not ...
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How much information is encoded in a ball on a field? [closed]
Consider a soccer ball placed on a planar field of finite dimension (just like a soccer field). How much information can be realistically encoded in the position of the ball on the field?
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Transmitting Data faster than the speed of light using entangled particles [duplicate]
If we have a pair of super-asymmetrical entangled particles, and move them a light year away so that they retain their quantum entanglement, and we set a clockwise spin (or vertical polarization) as 0 ...
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How is free energy in thermodynamics related to free energy in information theory/neuroscience?
Background
In thermodynamics, free energy refers to either Helmoltz ($U - TS$) or Gibbs ($H - TS$) free energy, the quantity that is minimised at equilibrium in a closed system maintained at constant [...
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Are all types of noise a result of lack of complete knowledge about the given system? What does this say about the physicality about information?
I am currently studying the basics of quantum information theory. When we study a system (classical or quantum), any undesirable influence out of our control is usually referred to as noise, and this ...
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Does information always gravitate?
I'm trying to wrap my head around Bekenstein's loose argument that a bit of information added to the black hole corresponds to an added Planck surface area to its horizon.
In it, he argues that one ...
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Compensating thermal entropy with informational entropy
Suppose you have a Maxwell demon scenario where particles in a box get sorted out by a goblin so that the entropy of the box decreases. Landauer (1960) proposes that the net entropy loss would be ...
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Do superluminal shadows drop the local temperature on distant objects?
There are lots of examples online of the scenario of someone with sufficient machinery casting a shadow of their thumb on the moon. It's argued the shadow travels faster than light, instantaneously ...
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How Taylor series is compatible with special relativity?
In mathematics, an analytic function is defined by its possession of a Taylor series with a positive radius of convergence ($R_c>0$). Notably, certain analytic functions—such as holomorphic ...
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Hawking Radiation paradox
How does Hawking radiation help in information conservation? Doesn't it create a paradox, as the particle-antiparticle pair created at the event horizon has nothing to do with the matter that has ...
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Information Loss in Chaos Theory
Is it accurate to suggest that in chaos theory, information is in practice lost due to the impossibility of characterizing the system's state with infinite precision, making it unfeasible to run the ...
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Black hole information paradox
I read that it is generally believed that information is preserved in black hole evaporation, and people's views only diverge when it comes to how information is preserved. Is this true?
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E. T. Jaynes and heat death
On E. T. Jaynes view, thermodynamic entropy of a system is, up to a multiplicative constant, the same as the the information entropy for the predicted distribution with maximum uncertainty conditioned ...
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Way to get information from inside black hole to outside?
So imagine a black hole the size of 100 km, and then there is a giant rod that is 50 km and pretends that the rod doesn't get broken due to tidal forces, and also assumes that the rod has a mini-robot ...
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Proving that a positive partial transpose (PPT) state is non-distillable
I am attempting to prove the following statement: A positive partial transpose (PPT) state cannot be distilled.
I would like to do so using the following facts:
Let $\rho$ represent a bipartite ...
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What's the limit on the length of string that can be pulled by a person? [closed]
Imagine it's pre-industrial times, and a king wants to keep control of his vast empire. One of the biggest problems was how slow it was to transmit information; it could take weeks to be notified of ...
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A version of Maxwell's Demon using Norton's dome to erase information for free?
Norton's dome is a thought expriment that shows Newtonian mechanics is non-deterministic. It has the shape of a dome (see exact details of its construction on the linked page) with a rather peculiar ...
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Why carrier wave cannot transfer information?
In the concept of wave modulation, I'm having trouble to understand why carrier wave cannot transfer information. My assumption is that the reason for that is due to the fact that the frequency, ...
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Fisher information of parametric channel
Suppose $\Phi_\theta$ is a quantum channel whose action can be written for any state $\rho\in \mathcal S(\mathcal H_S)$ in the Stinespring representation as $\Phi_\theta(\rho)= \text{Tr}_E(U_\theta (\...
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How does information 'move'? [closed]
Information cannot be transmitted faster than the light. However, I am confused about the meaning of 'transmission' of information. How does the information 'move'? If I calculate the future state of ...
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About information transmission speed [duplicate]
Einstein says information cannot be transmitted faster than light.
Say I set an alarm that ring at 9:00 am. I go to school, and wait until 9:00 am. Then I tell my friends that my alarm rang. If the ...
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Could information be transferred through a wormhole?
There was a paper published recently about the possibility of sending messages through a wormhole,see reference here. It has also been speculated that any entangled pair of particles—even particles ...
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Is there physical significance to the Gateaux derivative of entropy?
Is there any physical "force" generated by a difference in entropy or information between two regions? There is some confusion between thermodynamic entropy and information entropy, but one ...
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Entropy and information - Heat generation in computers
I understand that part of the heat release from a computer comes from resistive heating, but to my understanding it is also linked to entropy changes and information - such that even a superconducting ...
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Is the optimal POVM of a mixed state the same as the optimal POVM of the pure states in its ensemble?
If I have a mixed state, where each pure state in the ensemble has the same optimal POVM (by optimal I mean POVM for which the classical Fisher information is the same as the quantum Fisher ...
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Does the master equation break down for negative times?
I'm studying stochastic dynamics and have encountered the framework of the master equation for the study of continuous time Markov processes. First, I'll state some general definitions and then say ...
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The difference between classical and quantum entropies
The von Neumann entropy $-\mathrm{Tr}(\rho\ \log\rho)$ of a quantum thermal state with $\rho=\frac{1}{Z}e^{-\beta H}$ gives the thermal entropy, see e.g. this question.
The von Neumann entropy is a ...
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Does a shredded book contain more or less information (or the same) than the original book
If I shred a book into numerous pieces, and scatter them, so that the original text is completely unreadable, then for me, as a reader, the book has lost all its information. Its entropy has greatly ...
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Can, in theory, information escape an event horizon via a specialized setup?
Can, in theory, information escape an event horizon via a specialized setup?
Specifically, send a beam of photons to be barely—just barely—inside the event horizon, then wait for hawking radiation to ...
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Communication via entanglement [duplicate]
For years now i have in my haed a thought experiment for information exchange via quantum entanglement. And i am aware that something must be wrong with it but i can't figure out what it is.
The ...
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(Generalized) Jarzynski equality
Sagawa and Ueda ref, generalized the Jarzynski equality in the presence of a feedback control, leading to the following equation:
$$ \langle e^{-\beta(W-\Delta F)-I} \rangle = 1.$$
Can I interpret ...
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How information of accelerated charged particle travels, if photon is absorbed?
There is an electrostatic field around the electrically-charged particle (particle is the source of that field).
When the particle accelerates, it emits photon.
Photon travels at finite speed.
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Which theory can resolve black hole information paradox?
I am new, not have expert level knowledge.
But I have studied about black hole information paradox. The black hole doesn't kept any information which passes event horizon. Which can break physics.
Is ...
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Is the informational approach to thermodynamics generally accepted as "correct"?
This question is about the "ontology" as it were of statistical mechanics. In my limited reading of (equilibrium) statistical mechanics texts, I have encountered two viewpoints for what is &...
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Faster than light communication by entangled photons [duplicate]
Faster than light communication is not possible. If I measure the polarization of an entangled photon and it turns out to be right circularly polarized. In that instant, dont I know that someone ...