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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115 views

Could quantum randomness be transformed into classical, macroscale randomness?

If measurements of quantum phenomena can show results that are truly random wouldn't it be possible to establish a macroscale-dependence on such a non-statistical result and thereby introduce ...
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5answers
3k views

What triggers a nuclear decay?

I am not a physicist but I have been wondering about this: I understand that the decay of a nucleus is a random event and one cannot predict exactly when it will happen for a particular nucleus. ...
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0answers
15 views

Is quantum physics weirdness caused by our imperfect measuring tools and senses? [duplicate]

The more I learn about quantum physics the more it seems to me that it is not the "real" world that is weird but it's that quantum physics theory itself has inbuilt randomness that's caused by the way ...
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0answers
12 views

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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0answers
13 views

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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2answers
104 views

Flipping a coin with same initial conditions

Today, in my physics class my teacher was talking about how we can never predict the outcome of a coin flip. So I thought: Will the outcome of a coin flip be the same if we do not change the initial ...
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1answer
57 views

Randomly stopped dynamics of $x(t)$: How can I find $\text{var}\{ x(t) \}$?

Consider the simple dynamical equation $$ \dot{x}(t) = u H(t-\tau),$$ where the timescale $\tau$ is an exponentially distributed random variable $\tau \sim \omega \exp\{\omega \tau\}$ and $H(t) = 1-\...
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2answers
37 views

Can a perfectly symmetrical round bead dropped into a perfectly level Galton Board indefinitely balance on a peg?

Probability implies that "The Galton Board consists of a vertical board with interleaved rows of pegs. Beads are dropped from the top and, when the device is level, bounce either left or right as they ...
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1answer
93 views

Quantum Mechanics - How do we know that the observed locations of electrons are random? [duplicate]

How do we know that the observed location of a electron (or any quantum object) is purely random (there is no way to predict it) within the probability-function instead of normal randomness (we don't ...
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0answers
28 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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5answers
5k views

Is throwing dice a stochastic or a deterministic process?

As far as I understand it a stochastic process is a mathematically defined concept as a collection of random variables which describe outcomes of repeated events while a deterministic process is ...
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0answers
28 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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0answers
33 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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1answer
25 views

How to deal with motion on a 2-D lattice in terms of dimension?

I am reading a paper titled: Random walks of molecular motors arising from diffusional encounters with immobilized filaments. There the authors consider the molecular motor moving on a 1-D protein ...
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77 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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2answers
128 views

If the universe is random, why does it contain structure? [closed]

Ive read that the scientific community agrees on that the universe works in a non deterministic way. However, because we have some kind of structure in the universe I assume (from a super novice ...
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1answer
165 views

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
52 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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0answers
55 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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2answers
85 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
106 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
35 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
117 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
182 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
257 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
162 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
88 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
179 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
108 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
87 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
193 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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1answer
68 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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1answer
128 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
104 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
30 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
6k 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
6k views

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
143 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
83 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
117 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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0answers
90 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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1answer
213 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
161 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
249 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
382 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
340 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
468 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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0answers
61 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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1answer
86 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
991 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....