Questions tagged [fluctuation-dissipation]
The fluctuation-dissipation tag has no usage guidance.
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Thermal flunctuations of density in thermal equlibrium? [closed]
According to physics a fluid or gas in thermal equilibrium is not exactly homogeneous. Locally its density undergoes random fluctuations which are small compared to the corresponding equilibrium value....
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What is the relationship between persistence length and timescale?
I have calculated the bending persistence length of a polymer using MD simulations in the nanosecond timescale. The persistence length is long (410 nm) compared to the contour length (40-45 nm). But ...
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Are vibrating strings in string theory perpetual motion?
I have never learned string theory, so please forgive me if my question sounds naive or obvious, but I would like to know and I am most likely wrong.
As far as I know, strings vibrate in different ...
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How to calculate the thermal radiations of a seawater ball in the microwave range
I'm seeking for guidance on how to calculate the farfield spectral irradiance of the thermal radiations of an object made of a material with known complex permittivity ($\epsilon_r=\epsilon^{'}_r+j\...
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Calcuating Fluctuations in (Thermodynamic) Temperature in Microcanonical Ensemble
The definition of (Thermodynamic) Temperature is indeed possible in microcanonical ensemble through the Gibb's Entropy as shown in this work (1). In this scenario, the temperature, essentially a ...
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Fluctuational Electrodynamics: Ensemble Average
I am trying to understand the ensemble average often stated in the fluctuation-dissipation theorem describing thermal radiation:
Here, the overbar denotes the ensemble average. My question is, how is ...
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Time evolution operator with chemical potential
In the Bruus and Flensberg textbook, section 1.5, it is mentioned that
Basically, the result obtained from the canonical ensemble is carried over to the grand canonical ensemble by the substitution $...
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Virial theorem for momentum fluctuations
In the paper https://journals.aps.org/pr/abstract/10.1103/PhysRev.109.1464 Lebowitz attempted to derive an estimation of the magnitude of center of mass momentum fluctuations in the presence of ...
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Spontaneous emission as dissipation and fluctuation
Suppose we have some sort of medium and we want to build an effective theory of light inside. Of course we want to calculation the dielectric constant, which in turn is determined by the ...
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Why do statistical physics and thermodynamics care about fluctuations?
Fluctuation seems to be an eternal theme in the study of statistical physics and thermodynamics, why do we need to care about it? Just for stability?
Any comments would be appreciated
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Suscpectibility in Ising networks
I am struggling to find good references on how the susceptibility described phase transitions in Ising networks. First of all i struggle to find a good defintion for the susceptibility.
I understood ...
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A simple picture for work fluctuation relations?
One possible formulation of the second law of thermodynamics is that the work extracted during the change of a thermodynamic system between two thermodynamic states is at most equal to the free energy ...
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Relation between power dissipation and imag part of susceptibility [duplicate]
I am trying to understand the following relation between power dissipation and the imaginary part of the susceptibility, from Sethna's Statistical Mechanics textbook. Why does the integral equal the ...
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Deriving the fluctuation-dissipation theorem
In the derivation of the classical version of the fluctuation-dissipation theorem here, they expand the equilibrium distribution function (with Hamiltonian $H(x) = H_{0}(x) - f_{0}x$)
$$ W(x, 0) = \...
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Wiki video shows that vacuum fluctuations exist, despite that vacuum fluctuations do not exist
I have been reading this article about the quantum vacuum state, and in the section that I linked to, there is a video showing an experiment that shows visibly that quantum fluctuations are actually ...
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