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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.

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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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1answer
47 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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If we could replicate the universe we are in, is it possible that these two identical universes branch out? [duplicate]

Let's say we copied our universe exactly. Is there any randomness in play which will affect the universe?
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46 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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47 views

Self-averaging quantities in physics

This question is about self-averaging quantities in physics. For a definition see: https://en.wikipedia.org/wiki/Self-averaging. For concreteness I give an example below. Example Consider a ...
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2answers
51 views

Understanding entropy, information, and randomness

In a statistical mechanics book, it is stated that "randomness and information are essentially the same thing," which results from the fact that a random process requires high information. More ...
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3answers
82 views

Is wave function collapse the only source of 'randomness' in QM? What about field fluctuations? Are these two even distinct?

Basically I want to know the validity of the statement, "All randomness originates from wave function collapse" or maybe "The only true random event is the collapse of wavefunctions" This seemed to ...
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0answers
27 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
98 views

Weird results of Monte Carlo simulation

I'm simulating the 3D Ising Model using the Wolff update algorithm. I am using the Mersenne Twister RNG. When the lattice size is $L = 50$, the specific heat curve looks very weird!! I want to ...
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1answer
148 views

The entropy of lottery drawing machines

Suppose we have a fair lottery drawing machine where you have a container of numbered balls that is rotated many times such that interaction of the balls with themselves and the container produces a ...
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2answers
131 views

Does quantum randomness exist? [duplicate]

I just want to know if the quantum world is random. Or if the randomness is fully explained by measurement error. Or if it is just semantic. The previous questions are open to interpretation and do ...
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2answers
132 views

Is Quantum Mechanics Compatible with Conservation of Information?

What is exactly the law of conservation of information? In quantum mechanics we have truly random outcomes in experiments, but doesn't this randomness mean that new information is produced and the law ...
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3answers
69 views

What happens to a radioactive material's atom when it disintegrates?

Suppose you initial had radioactive $2^n$ atoms (where $n$ is an integer). Now after a number of halflives the number of left out atoms becomes 1. Now what will happen to it will it disintegrate and ...
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1answer
102 views

Langevin equation. What is the meaning of temperature?

Consider a system of $N$ particles, subject to some interaction potential $U$ (e.g. Lennard-Jones) and to thermal noise. The equation of motion is given using the Langevin equation: $$m_i \ddot{\bf r}...
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1answer
104 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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1answer
75 views

What do physicists mean when they say QM proves randomness?

Some physicists like Michio Kaku has said that the physics has proven randomness. Even some of my friends(they're not physicists) cite the Delayed Choice Quantum Eraser experiment and entanglement to ...
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1answer
121 views

Quantum computer vs. classical probabilistic computer

Is it possible to make a quantum computer from a perfect random number generator. I'm wondering if anybody that's studied it could make one from that type of random number generator.
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61 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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41 views

Why is this hard disk based-on true random number generator flawed?

I have been told that if one uses too small crystal sizes for the magnetic particles in a conventional hard disk, their magnetization would flip due to thermal agitation because the magnetic energy is ...
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1answer
119 views

Could the apparent non-determinism of Quantum Mechanics be explained with a universal pseudo-random number generator? [closed]

As a thought experiment, would it be logically plausible to claim that the apparent randomness of Quantum Mechanics could be explained by the existence of a universal and deterministic pseudo-random ...
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0answers
94 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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2answers
26 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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7answers
5k views

Are random errors necessarily Gaussian?

I have seen random errors being defined as those which average to 0 as the number of measurements goes to infinity, and that the error is equally likely to be positive or negative. This only requires ...
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9answers
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What exactly is deterministic in Schrödinger's equation?

I have read the following on Wikipedia but I can't understand it: In quantum mechanics, the Schrödinger equation, which describes the continuous time evolution of a system's wave function, is ...
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2answers
123 views

Does a randomizer break the law of causality?

I am reading this book why does $E=mc^2$ and I learned that causality is what proves that there is a cozmic speed limit-I'm the only one here who is astonished by the looks of it ;-). Anyway. Would a ...
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3answers
66 views

Simulation of multi-particle systems, randomness and chaos

The answer https://physics.stackexchange.com/a/10441/50677 for #2 (chaotic randomness) claims that the absolute knowledge (whatever that would be) of starting conditions were sufficient for a perfect ...
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0answers
87 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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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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1answer
115 views

Biased or Unbiased Random [closed]

I am confused with the concept of completely random actions. I was thinking of a very common statistical experiment in which we have a device or black box which randomly chooses between 1 and -1. If ...
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3answers
136 views

How can we certify that the randomness in the measurement outcomes is not due to randomness in the state preparation?

According to the theory of quantum mechanics, if a spin state is prepared along axis "x", and then measured along axis "z", then the result of the spin projection is probabilistic: half of the times ...
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1answer
174 views

Can Chaos Theory be used to explain the Ising model in paramagnetic phase?

Is it possible? How can I explain the randomness of spins in the paramagnetic phase with chaos theory? In this case, is the randomness apparent? If yes, I think the temperature would be a reasonable ...
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3answers
214 views

How do we know that certain quantum effects are random?

I was looking at a website that claims to generate random numbers from observation of quantum effects. This lead me to question how we know that the numbers are truly random. When we observe a ...
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3answers
247 views

Randomness of photon's spontaneous emission

I'd like to understand why the phase and the direction of a photon spontaneously emitted is random. Is there a "mathematical" rigorous proof of its randomness? I searched for a proof but couldn't find ...
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2answers
357 views

Randomness in Quantum Mechanics

Is the quantum world really random?How can one be sure that there are no variables that can actually predict the outcome like they do in Newtonian physics?
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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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1answer
66 views

Is a lightening strike deterministic?

This relates to a previous question: Is a dice roll deterministic? Essentially, I'm trying to get a better understanding of how quantum indeterminacy interacts with the macro world. It seems to me ...
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3answers
683 views

Is quantum mechanics truly probabilistic?

Probability arises inherently from a lack of information. For example, if I were to take a ball out of a bag with 3 yellow and 2 white balls, I would have a 0.6 probability of getting a yellow and a 0....
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1answer
149 views

Is there a consensus about the trueness of the randomness in QM? [duplicate]

I personally believe that there is a very strong case in favor of true randomness in QM but not being a physicist I would like to know from experts if there is a consensus about this. @John Rennie: ...
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3answers
701 views

How do we know that nuclear decay is truly random and spontaneous?

Nuclear decay is said to be random and spontaneous but how do we know for certain, that it is not just a lack of understanding of some other unknown force. Doesn't everything in the universe just ...
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1answer
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How do we know that radioactive decay is memoryless?

Let $\tau$ be the random variable that describes the lifetime of a given particle. It seems to conform to common-sense that $\mathbf{P}(\tau>t+s|\tau>s)=\mathbf{P}(\tau>t)$, as it would be ...
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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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4answers
521 views

Is the quantum world affected by the law of causality, or it is just really random? [closed]

If the quantum world is really random why a random quantum event 'e' happend in the way 'a' and not in the way 'b' . what caused that ?
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1answer
116 views

Is there even something like true randomness?

So a few months ago a research team did the following experiment: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.060401 They shot lasers at certain detectors trying to detect the spin ...
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1answer
217 views

Randomness and Thermodynamics

I am currently reading The road to reality by Roger Penrose. In chapter 27 he discusses time symmetry in dynamic evolution. He defines the Second Law of thermodynamics the following way: Heat flows ...
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1answer
51 views

Does quantum randomness allow extreme deviations like Gaussian randomness does?

{ I am explaining things as I know it. Please feel free to correct as necessary. } As I have understood it, Gaussian randomness forms a predictable pattern when sample size is very high. If we take ...
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1answer
150 views

Chess as random process [closed]

I asked this question at chess.stackexchange, but perhaps it is more suited here. This question might be equally applicable to other games which are not solved games and which have three outcomes: win/...
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1answer
238 views

References to Random Matrix Theory

I am looking for some good references - books/lecture notes/articles which contains Random Matrix Theory for Physicists. I am not particularly looking for mathematical rigor in derivations. I am more ...
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2answers
73 views

Randomly initializing ensemble of particles in “toy” computer model

I'm programming a "toy" model, and want to intialize the $(\mbox{positions},\mbox{momenta})$ of an ensemble of particles in three-space, using a uniform (pseudo) random number generator. But I'm a ...
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1answer
68 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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2answers
502 views

Why isn't the universe uniform? [duplicate]

I always have a question in my mind when I think about the big bang. It is that if the universe has expanded from a tiny singularity by an explosion to the universe of today, why didn't it expand into ...