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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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tautologies in phys: “speed of light is c” as “informational” [on hold]

Context: https://en.wikipedia.org/wiki/Tautology_(logic) https://en.wikipedia.org/wiki/Metre#Speed_of_light_definition https://en.wikipedia.org/wiki/Second#%22Atomic%22_second https://en.wikipedia....
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1answer
45 views

What do the area laws for mutual information and correlations actually state?

I am trying to understand what are the key points of this paper Area laws in quantum systems: mutual information and correlations. If I understand correctly the law states that the information ...
2
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2answers
65 views

E. T. Jaynes' subjectivism vs measurement of distributions

In his paper, E. T. Jaynes argues that entropy is a measure of our ignorance about a system. As such, the probability distribution of states $\{p_k\}$ has to be chosen in the most unbiased way, thus ...
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0answers
6 views

Relation between Fisher Information Matrix and Inertia Matrix

I have been wondering whether there is a relation between the Fisher Information Matrix in a stochastic particle system and Inertia Matrix?
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1answer
141 views

Why don't physicists interpret randomness in quantum mechanics as ignorance or limitations in our knowledge?

As the title says: why don't physicists interpret randomness in quantum mechanics as ignorance or limitations in our knowledge? Why is the randomness in quantum mechanics equations not added to the ...
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0answers
14 views

information conservation

Since according to the unitarity principle the total amount of information in the universe is conserved over time, how was this information generated ? Is there a relationship between energy ...
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2answers
101 views

Why is information indestructible in quantum mechanics? [duplicate]

Why is information indestructible in quantum mechanics?
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1answer
48 views

Information Density of Spacetime [closed]

How much information is required to completely describe a given volume in spacetime?
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0answers
38 views

Bekenstein Bound / Holographic Principle at Extremely Low Temperatures

I'm curious about a possible connection between the Berkenstein Bound and the physical nature of information, specifically in reference to the fact that the amount of information that can be written ...
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0answers
7 views

Entropy of superposition state vs collapse

Imagine 2 similar atoms one is in superposition state while another is collapse into 1 of the possible States fall into the black hole at the same time, do the 2 atoms lost equal amount of entropy? I ...
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0answers
32 views

Relationship between physical and information entropy [duplicate]

This question is inspired by the following example given in Barnett's book on quantum information: (PDF here, starting at the bottom of page 5) I am not a physicist, but I'll accept that the ...
2
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0answers
55 views

Is information conserved in an expanding universe?

From the classical and quantum mechanical viewpoint, is information conserved in an expanding universe or not?
2
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3answers
106 views

Why does less knowledge imply more correlations?

Given two systems, correlations quantify how much information we can gain about system 1 by measuring system 2. Entanglement is a type of correlations which only occurs in quantum mechanics. There ...
2
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1answer
69 views

Is the total information in the (visible) universe compatible with the one on the surface of a black hole with the same radius?

Is the total information available in the universe compatible with the entropy we would find on the surface of an hypothetical black hole whose radius is the visible universe one ($\sim14$ Gpc)? We ...
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3answers
4k views

Why is the information paradox restricted to black holes?

I am reading Hawking's "Brief answers". He complained that black holes destroy information (and was trying to find a way to avoid this). What I don't understand: Isn't deleting information quite a ...
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3answers
205 views

Is there a physical limit to memory reading and writing speed?

Is there a limit to the speed at which a memory, quantum or classical, can be read or written into? I've seen this interesting question : Is there a physical limit to data transfer rate?. Here I'm ...
8
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4answers
2k views

No FTL information implies no FTL travel?

The general consensus in the scientific community is that it is impossible to transmit information faster than light. There is also speculation that it might be possible to open wormholes or travel ...
1
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1answer
82 views

What is the physical interpretation of the action integral, without the stationary action principle?

I'm still wondering about the physical interpretation of the action integral of some mechanical system (classical theory here, to simplify things): \begin{equation}\tag{1} A = \int_{t_1}^{t_2} L(q, \, ...
4
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2answers
121 views

Can the second law of thermodynamics be derived from Quantum randomness?

The second law of thermodynamics says that the entropy of an isolated system continuously increases. Can we say that this is due to Quantum mechanics, which continuously increases the information ...
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0answers
26 views

information theory and energy mass relationship (E=mc2) - just a hunch … [closed]

I was walking on the street the other day and thought to myself, maybe E=mc2 can be derived from information theoretic principles. I did not do too much work on this, just want to brainstorm a bit. ...
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9answers
2k views

What precisely does it mean for “information to not travel faster than the speed of light”?

This is something that's been bothering me for a while. The way we usually first hear about causality is that "nothing travels faster than $c$". But then you learn that phase velocities can ...
3
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0answers
42 views

Why can't the Schwarzschild radius be larger than the Compton wavelength?

In the second paragraph of the third page of this paper, the author makes a statement The dynamical process must now involve, not the length scale $R_{s}$, but rather the universal length $L_{CS}$....
2
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1answer
122 views

Is this a correct derivation of the second law or it is just nonsense?

In this article, the author makes the following argument. The difference between entropy and information is that entropy is the bits that you don't understand while information is the bits you do ...
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1answer
45 views

Bekenstein bound and black hole

I'm confused with this sentence from Wikipedia: "Upon exceeding the Bekenstein bound a storage medium would collapse into a black hole." Does that mean "the storage medium will become a black ...
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2answers
85 views

Paragraph from a Stephen Hawking's Book (Uncertainty Principle)

This is from a Stephen Hawking's Book (Uncertainty Principle). I would like to know how does the Uncertainty Principle impose a limit on the size. What does he mean? From Hawking's book: It turns ...
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1answer
53 views

Nielsen and Chuang 2.2.3: state of a qubit after measurement

(Apologies for the poor typesetting of kets. I haven't been able to figure out how to do that on this site). On page 85 of Nielsen and Chuang's textbook, they write that the probability of obtaining ...
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2answers
49 views

Is information lost in the Heisenberg's uncertainty?

If I set a particle at a known momentum and a known position, then I would expect that I know the precise position and momentum upon measurement (assuming I can measure that well). The uncertainty ...
0
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1answer
75 views

Why is the term “information” used to describe a physical system [duplicate]

(With apologies that my physics background is minimal...) Why is the term "information" used to describe a physical system, such as the movement of air through a jet engine? If I understand ...
3
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0answers
50 views

Is it necessary to assume that equivalent microstates cannot get transformed into inequivalent microstates to derive the Landauer principle?

The Landauer erasure principle states that to erase a bit of information from a system, the entropy of the environment will be increased by at least $k_B\log2$, or equivalently, it costs at least an ...
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0answers
35 views

In digital physics, how would additional information such as velocity be encoded into bits? [closed]

Assuming that at the bedrock of reality, there is some unary particle from which everything is derived, such that there either is a unary particle in some space or there isn't, how would information ...
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2answers
79 views

How to handle bra-ket in logarithm?

$\newcommand{\ket}[1]{\left| #1 \right>}$ $\newcommand{\bra}[1]{\left< #1 \right|}$ Say the following two equations: $$ S = - k_B \text{Tr} (\rho \ln \rho) $$ $$ \rho = \sum _\epsilon \ket{\...
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2answers
50 views

Energy that can control itself (A unit that can process information without body) [closed]

I read a book called The future of the mind. There it suggested a conscience that exists in the form of energy without body. Ideally, I thought the energy without body may take the form of light. ...
2
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1answer
64 views

Von Neumann entropy of a quantum state vs Von Neumann entropy of a system

Using the Chuang and Nielsen Quantum Computation and Quantum Information book, for an introductory course in Quantum Information, I stumbled on an ambiguous (at least for me) use of the Von Neumann ...
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1answer
59 views

Information to Energy equations?

Are there are any known formulas or equations that can calculate information from energy or energy from information? One of them, I believe, is the Bekenstein bound which is the maximum information ...
2
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2answers
145 views

Why does information loss in quantum collapse not threaten determinism?

When Hawking argued that information is lost in black holes, this triggered the "black hole war" because it threatened determinism, which would mean the laws of physics are only true on average. But ...
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0answers
46 views

Are strings capable of information processing? If so would string computers be more powerful than quantum computers?

A deterministic computer is weaker than quantum computer at least quadratically for (almost) all kinds of tasks. This is proved and the difference arises from Grover's search algorithm, which allows ...
2
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0answers
31 views

What is all the known information contained in thermal noise?

I've read up a little bit on thermal noise, which is an unavoidable noise in materials when $T>0K$. Thanks to this noise, by measuring the voltage across a material, it is possible to extract the ...
1
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1answer
64 views

What is the relation between uncertainty and information obtained from a measurement?

For ex. if a measurement gives a position with twice the uncertainty as another measurement, how much less information regarding position are you getting? In other words, if uncertainty doubles, is ...
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0answers
27 views

Possible to canonically digitize analog data to create public RNG?

Suppose you have a random data source, for which different observers will often, but not always, agree on a digitization. E.g. how many sun spots are visible from Earth right now, or what's the ...
2
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1answer
19 views

If mass and energy are same what will be the equivalent of a homogeneous ball in terms of energy and information?

We can observe an object with mass as it has a well defined boundary but it is not the same with energy. What may happen to the information or data that exists with an object and is needed to ...
3
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2answers
68 views

Why is it necessary to irreversibly erase a memory?

I know that the most accepted resolution of the Maxwell's demon paradox was proposed by Landauer and revolves around the fact that the demon's memory is finite and will have to be erased at some point....
2
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0answers
27 views

How does the information content in a holographic world add up?

I watched Leonard Susskind's great layman lecture "The World As Hologram" the other day (https://www.youtube.com/watch?v=2DIl3Hfh9tY) and it kind of makes sense to me. If Information is a conserved ...
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0answers
32 views

Why can't I surpass the holographic limit by stitching together two surface areas?

Suppose I have a rectangular brick of computer memory. My brick is very thin on one side and contains so much memory that it is just one bit away from being a black hole. According to the holographic ...
3
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1answer
65 views

Information loss in black holes

Doesn't quantum collapse or decoherence mean that information is being lost all the time? So why is the loss of information in black holes such a big deal?
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0answers
58 views

How come no information can travel faster than light when we can measure a black hole's mass? [duplicate]

So I learned about the Schwartzchild radius, which is the radius of an object's event horizon. But how we define an event horizon is that it's a region of space where the gravitational acceleration ...
1
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1answer
73 views

Amount of Information of a Galaxy? [closed]

Just like the title suggests, how much data/information does a galaxy have in (bits)? Like the Milky Way galaxy for example?
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2answers
223 views

Bekenstein Bound

This info is from Wikipedia In physics, the Bekenstein bound is an upper limit on the entropy S, or information I, that can be contained within a given finite region of space which has a finite ...
1
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1answer
197 views

The 'Conservation of Information' myth

PBS Spacetime recently released a video talking about 'why information is never destroyed in Quantum Mechanics' I'm surprised to see this myth to persist even to this day. We know that unitarity and ...
2
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0answers
31 views

Information density, Bekenstein Bound, and length contraction

Is it possible to observe a region of space that has information density greater than what the Bekenstein Bound will allow when length contraction is involved? I.e. An object travels through the ...
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2answers
62 views

Contradiction of the extension of the electric field of a charge to infinity

The usual point of view is that the electric field is distributed to infinity and the information about displacement of a charge translates to every other charge in the universe with the speed of ...