Physics Stack Exchange
Physics Stack Exchange

Questions tagged [fluctuation-dissipation]

91 questions
35
votes
16 answers

Can a broken egg spontaneously reassemble itself (as in the video)?

According to the fluctuation theorem, the second law of thermodynamics is a statistical law. Violations at the micro scale, therefore, certainly have a non-zero probability. However, the application of the theory, in particular the Jarzynski…
kbakshi314
  • 2,430
18
votes
3 answers

What information is contained in the quantum spectral density?

Consider a harmonic oscillator system with Hamiltonian $$\hat{H} = \frac{1}{2} A \hat{u}^2 + \frac{1}{2} B \hat{v}^2 \qquad [\hat{u}, \hat{v}]=i \gamma $$ where $A$, $B$, and $\gamma$ are all real. This system has resonance frequency $\omega_0 =…
DanielSank
  • 25,766
12
votes
2 answers

Does the fluctuations-dissipation theorem hold in active matter for macroscopic physical quantities?

I am trying to understand how the fluctuation–dissipation theorem applies to active matter. I simulated a system with active motors which may consume energy from the environment to move and exert force on fibers. All the chemical reactions have…
0x90
  • 3,456
11
votes
1 answer

Self-Contained Explanation of the Fluctuation-Dissipation Theorem?

While studying statistical mechanics, I came across the Fluctuation-Dissipation Theorem, which is introduced in various contexts and applications. It seems to be a very important concept. However, I've noticed that it is often presented in different…
K.R.Park
  • 456
11
votes
2 answers

Quantum shot-noise and the fluctuation dissipation theorem

Classically, shot noise observed in the signal generated by a laser incident on a photodiode is explained as being due to the quantization of light into photons, giving rise to a Poisson process. In quantum optics, on the other hand, the shot noise…
nibot
  • 9,691
11
votes
2 answers

Nonequilibrium thermodynamics in a Boltzmann picture

The Boltzman approach to statistical mechanics explains the fact that systems equilibriate by the idea that the equillibrium macrostate is associated with an overwhelming number of microstates, so that, given sufficiently ergotic dynamics, the…
Jess Riedel
  • 3,764
9
votes
1 answer

Fluctuation-dissipation theorem and Kramers-Kronig relations

Is there any connection between fluctuation dissipation theorem and Kramers-Kronig relations? They are often described together under linear response theory but I do not see any exact connection (like one being special case of another).
Tomasz
  • 121
7
votes
2 answers

Fluctuation-dissipation theorem in the Keldysh formalism

In Kamenev's book Field Theory of Non-Equilibrium Systems (he also has lecture notes online here, which contains the relevant statement on pg. 17), he states that the following equation $$G^K(\epsilon) = \coth\left(\frac{\epsilon-\mu}{2T}\right)…
Henry Shackleton
  • 1,092
7
votes
1 answer

How does the fluctuation theorem dissipation function become entropy?

In "The Fluctuation Theorem" by Evans and Searles, they derive the transient fluctuation theorem from Liouville's theorem (pg 1541). Following their notation $ \Gamma = (\vec{q}, \vec{p}) $, they use Liouville's theorem and the continuity equation…
user92177
7
votes
3 answers

How to include random force in the simulation (Classical Molecular Dynamics)

I need to implement a random force in my code according to the fluctuation dissipation theorem. I have a Gaussian distribution function ready width average 0 and distribution 1 and I know I need to multiply it by something but I'm not sure what. The…
Yotam
  • 711
  • 1
  • 5
  • 15
7
votes
3 answers

What happens if you connect a hot resistor to a cold resistor?

Kind of an extension to this question: If you heat up an object, and put it in contact with a colder object, in an ideal insulated box, the heat from one will transfer to the other through thermal conduction and they will eventually reach an…
endolith
  • 5,784
6
votes
2 answers

Fluctuation dissipation theorem : how to identify the response variable and the force in general?

I fully re-edited my question I have a super basic question. Note that I am just beginning to learn linear response theory. General context: If I consider a linear, time invariant, causal system, relating an input $E$ to an output $S$, I know that…
StarBucK
  • 1,688
6
votes
2 answers

Equivalence of thermodynamic ensembles

It is often argued that thermodynamic ensembles are equivalent in the sense that no matter what ensemble one uses for the calculations, one should end up in the same macroscopic equations of state. This is due to the fact that distributions are…
Botond
  • 1,026
6
votes
1 answer

Does the skin effect, eddy current / hysteresis losses contribute to Johnson noise in an inductor?

Based on my very basic understanding of the Johnson noise, it's not just a DC phenomena, but should change with frequency in a system, where there is a frequency dependent, real component to the impedance. I think both the skin effect and eddy…
Someone
  • 63
5
votes
2 answers

Question about thermodynamic conjugate quantities

I've come across the Onsager reciprocal principle. It's almost clear, except for thermodynamic conjugate quantities - what's that, physical meaning (except the formal definitions: $X_i = -\frac{1}{k}\frac{\partial S}{\partial x_i}$, which isn't…
m0nhawk
  • 1,009
1
2 3 4 5 6 7