Questions tagged [randomness]

Randomness covers questions having to do with the concept of randomness in physical processes and questions about determinism vs indeterminism or interpretations thereof. Question related to concepts of probability may also use this tag.

28 questions with no upvoted or accepted answers
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Temperature as the independent variable of Lagrangian

I was thinking about applications of the Lagrangian and I started to toy with some ideas and tried to come up with interesting twists. Immediately I thought it would be interesting to use temperature ...
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21 views

What is the Spectral Form Factor?

In many papers in Random Matrix Theory [1-3] related to quantum chaos (and, in particular, to the SYK model) they analytically continuate the partition function of the system $Z(\beta)$ into $Z(\beta +...
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27 views

How to introduce dimensionality in a dimensionless framework?

This question is an extension of this one. I have been told that to introduce dimensionality in a dimensionless quantity I need to multiply with suitable parameters. For instance, for velocity I have ...
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52 views

Are particles in a perfect fluid in random motion?

A perfect fluid has no heat conduction, but it exerts pressure in all directions (according to stress-energy-momentum tensor). If it does not conduct heat, then it means it does not have random ...
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1answer
105 views

Reconcile a pair of two-qubit boundary-state separability probability analyses

It is now clearly well-established--though formalized proofs are still largely lacking—that the probability, with respect to Hilbert-Schmidt measure, that a generic two-qubit state is separable/...
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99 views

One consequence of the ergodic hypothesis?

this is my first question here, and I'm trying to self-learn physics from Kip Thorne's 2017 textbook "Classical Physics". IF I understand the ergodic hypothesis correctly, it is simply the statement ...
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84 views

Interpretation of quantum superposition and classical Brownian motion

In the standard, Copenhagen interpretation of quantum mechanics, the usual ontology assigned to the phenomenon that repeated measurements of a quantum mechanical observable yielding different results ...
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58 views

Prove that the randomness of the spins of entangled quantum particles is not due to periodic factors?

I just learnt about entangled particles in a lecture today. According to the theory, the probability of the spin of an entangled particle is 50/50 (spin up or down), and is only determined when ...
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23 views

Is it possible to compute the kubo conductivity of bosons in disorder via mean-field theory?

The kubo conductivity is computed essentially from the current-current correlation function. This works fine when there is no or a periodic potential, as there are a number of ways that can be found ...
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36 views

Global Random Bits from Nature

I would like to get a few random bits per day from nature (from chaotic physics, like rolling dice, or quantum physics, but not from cryptography) which Alice and Bob can measure independently from ...
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45 views

Numerically integrate equations of motion with noise

Consider the equations of motion $$\begin{cases} \dot{x}(t) & = v(t) \\ \dot{v}(t) & = -\frac{\lambda}{m} v(t) + \frac{1}{m}F^{c}(x(t)) = a(x(t), v(t)) \end{cases},$$ where $x$ is the ...
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81 views

How to quantify the level of non determinism / randomness in the universe

I recently read a little about the Bell test (I'm not a physicist, but reasonably well educated) and I started wondering if there is a way to express the level of non-determinism as a single number ...
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68 views

phonon dispersion with random masses

In order to see how phonons should be affected by disorder, I've been playing around with a model involving a 1D chain of masses linked by springs, where the spring strengths are all the same but the ...
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181 views

In the process of Diffusion Limited Aggregation (DLA), why do the particles prefer to form something which has the shape of a tree?

In the process of Diffusion Limited Aggregation (DLA), why do the particles prefer to form something which has the shape of a tree instead of just a front line?
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Question on the correlation function of dichotomous Markov noise

Setup: A two-state switching process $I(t)$ between two values $\Delta_1$ and $\Delta_2$ with rates $\alpha$ and $\beta$ can be represented by the transition probabilities $$ P_{ij}(t) = \frac{1}{\...
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Dynamics subject to an alternating step/rest sequence with two different resting intervals

Consider that a particle is either in motion (with velocity $u$) or at rest: $$ \dot{x}(t) = u S(t) $$ where $S(t)$ is a switching process between $0$ and $1$. This switching is defined as follows. ...
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31 views

A case where entanglement leads to correlation in decay time

Half-lives of unstable or metastable states are typically known, but specific decay times are inherently uncertain. On the other hand, quantum entanglement leads to correlations between inherently ...
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73 views

Is the “probabilistic nature of quantum mechanics” and quantum randomness the same?

Digital Physics are a branch of hypotheses about the fundamental physics of our universe. They basically describe the universe as an analogy to a computer and defend that everything in the universe is ...
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1answer
51 views

Gaining intuition about summing over random basis vectors in random matrix theory

I'm currently reading the following reference on eigenstate thermalization and chaos in quantum mechanics: https://arxiv.org/abs/1509.06411 I'm confused by a derivation that I think is very important ...
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33 views

Why the distribution of Fluctuationg force in brownian motion has gaussian distribution?

I am reading the Zwanzig's book and I have a confusion about the average of the fluctuating force and its distribution. As it says $F(t)$ is a random variable that means it has a probability ...
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1answer
67 views

Randomness - Quantum Mechanics

If there is pure probabilistic randomness for quantum particles, why isn't this randomness seen in macroscopic objects too, after all they are made up of quantum particles? Why and How does this ...
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29 views

probability distribution of dependent random variables

If we have dependent random variables, then what how is the distribution the pdf look like? Can it be a normal distribution? For example, additive white Gaussian noise (AWGN) has a normal distribution,...
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106 views

Movement of a random walk in the limit (a particle in diffusion)

I asked this question in Math Exchange and MathOverflow and obtained no answer. This question may lack of mathematical rigorous, but I would like to understand why this type of reasoning is sometimes ...
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1answer
69 views

Why can I unfasten the random knots of my earphones by vibration up and down?

Very often I just put my earphones in my pocket carelessly when I walk to my school from my home. The next time I want to use it which always has so much stochastic and fasten knots tightly. But don'...
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68 views

Volume of cubes thrown in a container

I am trying to calculate how many lego bricks I can fit in containers of a given sizes. Basic 1x1 lego brick is 8 x 8 x 9.4 mm so it has a volume of ~600 mm² Then we have a container of size 192 x ...
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195 views

Probability of collision of brownian particles

2 Brownian particles in a volume $V$. I wish to compute the probability that a collision occurs during a time $dt$. This should be a function of $V$ and the diffusion coefficient $D$. The result ...
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59 views

Can plasma in a Plasma ball be used as a source of true randomness?

This is just a thought but I've been staring at the Plasma Ball on my desk for a while and after a while I realized the plasma rays/waves/beams seem to be generated in a different spot each time so I ...
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1answer
67 views

Randomness of submolecular phenomena

Why do models of submolecular phenomena involving randomness work? Do these phenomena appear random to other submolecular particles? For example, people can use Einstein-Smoluchowski to characterize ...