A important property of all systems in thermodynamics and statistical mechanics. Entropy characterizes the degree to which the energy of the system is *not* available to do useful work
2
votes
1answer
112 views
free energy and entropy of 2D soap froth
This is a (exploratory) computational project. The soap froth was created by injecting bubbles into a chamber formed by two rectangular plates which are 0.16cm. From the moment the soap froth was ...
3
votes
1answer
158 views
Why is (von Neumann) entropy maximized for an ensemble in thermal equilibrium?
Consider a quantum system in thermal equilibrium with a heat bath. In determining the density operator of the system, the usual procedure is to maximize the von Neumann entropy subject to the ...
2
votes
2answers
161 views
Entropy exchange of a free fall
I have a problem in which the tell me that you drop a bag of 50 kg of sand from 10 meters high, and you have to caltulate the entropy difference of the sand, asuming that the speific heat of the sand ...
5
votes
3answers
550 views
Entropy and the principle of least action
Is there any link between the law of maximum entropy and the principle of least action. Is it possible to derive one from the other ?
-4
votes
3answers
444 views
Can heat be extracted and concentrated? [closed]
If one could devise an answer to this question, electricity would be free for everyones disposal. (seems like a good dream but in reality free energy will be this worlds downfall)
3
votes
5answers
647 views
For an isolated system, can the entropy decrease or increase?
In any sizable system, the number of equilibrium states are much, much greater then the number of non-equilibrium states. Since each accessible micro state is equally probably, it is overwhelmingly ...
3
votes
2answers
453 views
Can ice have a higher entropy than water?
I've leant that entropy is a state of randomness, and that solids have a more structured form, therefore having less entropy.
However, I saw a YouTube comment stating the following:
a liquid NOT ...
2
votes
1answer
119 views
The definition of entropy
As history of thermodynamics say, it was a mystery that what is the required condition for a given energy conversion to take place? Like there are two possible events each conserving energy but only ...
1
vote
1answer
170 views
Isentropic Processes
I'm having trouble understanding why reversible adiabatic processes are isentropic.
I understand that in a reversible adiabatic process there is no heat exchange and so $dQ = TdS = 0$. However, if ...
3
votes
1answer
62 views
Relation between Casimir and hydrophobic effects
Background
Some years ago I was studying "Fundamentos de biología" (Biology fundamentals) and learned how the lipids create a bilayer due to the water repulsion. Some time later I learned that this ...
1
vote
2answers
231 views
Entanglement Entropy
I needed some references which involves, the basic definition and motivation for Entanglement Entropy, and its one or two applications to many-body physics/black holes.
2
votes
2answers
424 views
Entropy Change During Reversible Processes
I'm confused about the Second Law of Thermodynamics. The Second Law of Thermodynamics prohibits a decrease in the entropy of a closed system and states that the entropy is unchanged during a ...
0
votes
0answers
193 views
Entalpy and entropy role in freezing-point depression phenomena
There's this "atomic" explanation of the freezing-point phenomena on Wikipedia that leaves me really intrigued.
Consider the problem in which the solvent freezes to a very nearly pure
crystal, ...
4
votes
1answer
87 views
Where and how is the entropy of a black hole stored?
Where and how is the entropy of a black hole stored?
Is it around the horizon? Most of the entanglement entropy across the event horizon lies within Planck distances of it and are short lived.
Is ...
0
votes
0answers
39 views
Entropy of binding two rigid bodies together in a closed system (e.g. forming a diatomic out of two monatomic gas particles)
When I bind two molecular complexes together, or in the simplest case, form a diatomic out of two atoms in a monatomic gas, the entropy of my (closed) system will decrease. We can perhaps understand ...
0
votes
0answers
93 views
Is it possible to add heat to a monoatomic ideal gas without increasing entropy? [closed]
The Sackur-Tetrode equation expresses the entropy of a monoatomic ideal gas:
[Equation from HyperPhysics]
9
votes
1answer
39 views
Renyi fractal dimension $D_q$ for non-trivial $q$
For a probability distribution $P$, Renyi fractal dimension is defined as
$$D_q = \lim_{\epsilon\rightarrow 0} \frac{R_q(P_\epsilon)}{\log(1/\epsilon)},$$
where $R_q$ is Renyi entropy of order $q$ ...
6
votes
2answers
188 views
Renyi entropy in physical systems
We know that the Shannon entropy $H(P)=- k_{\mathrm{B}}\sum_i p_i \ln p_i$ is mostly the entropy of the thermodynamic systems.
Does the Renyi measure $H_{\alpha}(P)=\frac{1}{1-\alpha}\log \sum ...
11
votes
5answers
674 views
Why does the nature always prefer low energy and maximum entropy?
Why does the nature always prefer low energy and maximum entropy?
I've just learned electrostatics and I still have no idea why like charges repel each other.
...
5
votes
0answers
88 views
Geometric entropy vs entanglement entropy (dependent on curvature coupling parameter)
I have a quick question. In hep-th/9506066, Larsen and Wilczek calculated the geometric entropy (which I believe is just another name for entanglement entropy) for a non-minimally coupled scalar field ...
1
vote
1answer
45 views
How does quantum entropy scales with the size of the sample?
Suppose i have a 3D bulk of physical matter with no black holes enclosed in a sphere of radius $R$. What is the scaling law of all quantum entropy in function of $R$?
If the scaling is not $R^2$, in ...
3
votes
2answers
429 views
Can entropy be equal to zero?
I've searched for it but I only found contradicting answers from "scientists":
Mr. David Balson, Ph.D. states: "entropy in a system can never be equal to zero".
Mr. Sam Bowen does not refutes the ...
1
vote
1answer
99 views
Entropy of a mass arrangement around the earth
An mind experiment, taking the entire Earth as an isolated system
Then this is the initial state:
N masses are distributed around the earth, at different height.
(for example we can use a single ...
4
votes
1answer
85 views
name of experiment
I'm seeking the name of or reference for an experiment I once saw in a college physics class. At the beginning of one class the instructor repeatedly wound a wiper that spread a blot of some type of ...
2
votes
0answers
215 views
Influence of Joe Rosen work, is it marginal, or significantly accepted?
I have prepared a paper that relies on work of Joe Rosen on symmetry (e.g. "Symmetry Rules: How Science and Nature Are Founded on Symmetry"). I am wondering about his influence. For example, when I ...
2
votes
4answers
351 views
How does the introduction of living things into a closed system affect the rate of change of entropy?
Does the introduction of living things into a closed system increase or decrease the overall rate of change of entropy of a system?
3
votes
2answers
236 views
How would we perceive time going backwards?
I haven't taken Physics in University. Lately, I've been reading about some of the branches of physics through Wikipedia. I read several times that many of the theoretical models do not explain why ...
1
vote
0answers
44 views
What other factors effect the ability of a propigating field of pressure in a gaseous medium to predict gravitational collapse?
What other factors effect the ability of a propigating field of pressure in a gaseous medium to predict gravitational collapse?
Will the only factor influencing the Speed of Sound in this medium be ...
2
votes
2answers
120 views
Speed of Entropy change
If time in systems moving with different speed goes differently, does speed of entropy change differ in these systems?
(is "speed of entropy change" a valid term? can we compare them?)
4
votes
3answers
339 views
How are possible microstates discerned in Gibb's entropy formula?
On the entry of Gibb's entropy formula on Wikipedia, the following definition is given: "The macroscopic state of the system is defined by a distribution on the microstates that are accessible to a ...
2
votes
1answer
278 views
Physics-based derivation of the formula for entropy [duplicate]
Possible Duplicate:
Proof of $S=-\sum p\ln p$?
I am looking for a derivation of the formula
$$S~=~-\Sigma_ip_i \log (p_i).$$
for entropy, from first principles. I only wish to assume the ...
12
votes
3answers
1k views
How do you prove $S=-\sum p\ln p$?
How does one prove the formula for entropy $S=-\sum p\ln p$?
Obviously systems on the microscopic level are fully determined by the microscopic equations of motion. So if you want to introduce a law ...
3
votes
2answers
274 views
Can entropy be explained in terms of a cleaning/keeping your room clean?
I'm trying to relate the concept of entropy to keeping my room clean as suggested by my high school teacher ~1993...
Comparing the two scenarios:
Every day I come home and throw an empty can on the ...
1
vote
2answers
145 views
Activation energy and entropy
First assertion
If a system is already in a high temperature, adding energy, will increment the entropy in a low amount (compared with a system in a lower temperature).
Question (if assertion is ...
2
votes
2answers
316 views
The definition of entropy in quantum mechanics
I have seen entropy with several different definitions. Like Von Neumann entropy and Rényi entropy, etc.
So I am curious why there are so many different definitions in quantum mechanics while only ...
5
votes
3answers
2k views
Why does maximal entropy imply equilibrium?
From a purely thermodynamical point of view, why does that entropy have to be a maximum at equilibrium? Say there is equilibrium, i.e. no net heat flow, why can the entropy not be sitting at a ...
0
votes
1answer
332 views
Does the Higgs Mechanism contradict Entropic Gravity?
Does the Higgs Mechanism contradict Entropic Gravity?
It seems like it probably does. But then again, one is a microscopic theory and the other is macroscopic. Can they live together in harmony? or ...
5
votes
1answer
264 views
Motivation for maximum Renyi/Tsallis entropy
The Conditional limit theorem of Van Campenhout and Cover gives a physical reason for maximizing (Shannon) entropy.
Nowadays, in statistical mechanics, people talk about maximum Renyi/Tsallis entropy ...
3
votes
1answer
184 views
Do laws of thermodynamics have a place in Theory of Everything? [closed]
I am having a difficulty understanding why second law of thermodynamics is still a valid universally accepted concept. I understand it works on paper for describing isolated heat systems. However, I ...
13
votes
4answers
859 views
Entropy of radiation emitted into space
In several papers I see something equivalent to the following expression for the entropy of radiation given by an astronomical object such as the Sun (assuming the object can be approximated as a ...
5
votes
1answer
219 views
Energy formula for separating $O_2$ from mixture of $O_2$, $NH_3$ and $H_2O$
I have a physics problem I'd like to make sure I get correct.
The practical aspect of this problem is that the photosynthetic efficiency of algae is inhibited with dissolved O2 in the growth medium, ...
1
vote
0answers
115 views
An explanation for the Landauer's principle
Has anyone understood the Landauer's principle? What is the current status?
In specific, is there a theoretical derivation of the Landauer's Principle?(not the heuristic one based on Salizard's ...
19
votes
3answers
126 views
Does entropy measure extractable work?
Entropy has two definitions, which come from two different branches of science: thermodynamics and information theory. Yet, they both are thought to agree. Is it true?
Entropy, as seen from ...
2
votes
1answer
116 views
Minimal Maxwell's Demon
I would like to understand where the waste heat is generated in the Maxwell's demon problem. To this end I've come up with the simplest scenario I can think of. If my scenario is workable I am hoping ...
3
votes
3answers
302 views
Formal demonstration that minimizing the free energy equals maximizing the entropy
I never had great intuition when it came to thermodynamic concepts and potentials even though reading a textbook and completing the exercises has never been a huge problem.
In one of them, I was ...
2
votes
1answer
292 views
Why does the law of increasing entropy, a law arising from statistics of many particles, underpin modern physics?
As far as I interpret it, the law of ever increasing entropy states that "a system will always move towards the most disordered state, never in the other direction".
Now, I understand why it would ...
10
votes
4answers
586 views
Ignorance in statistical mechanics
Consider this penny on my desc. It is a particular piece of metal,
well described by statistical mechanics, which assigns to it a state,
namely the density matrix $\rho_0=\frac{1}{Z}e^{-\beta H}$ ...
3
votes
4answers
241 views
Does entropy decrease through measurement?
For an electron in its rest frame, we have an entropy
$$
S = \log 2,
$$
which comes from the 2 possible spin directions along z-axis.
If the measurement $S_z$ changes its state to $\left| + ...
0
votes
2answers
103 views
Qualitative discussion about entropy and disorder
Many discussions about entropy and disorder use examples of decks of cards, pages of books thrown in the air, two gases being mixed in a container, even the state of a nursery at the end of the day ...
5
votes
2answers
939 views
Why do reversible processes not increase the entropy of the universe infinitesimally?
The book Commonly Asked Questions in Thermodynamics states:
When we refer to the passage of the system through a sequence of internal equilibrium states without the establishment of equilibrium ...
