# 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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### Statistically stationary, periodic random process

As I understand in a statistically stationary process, the statistics are invariant under a shift in time. It is natural to assume that the statistics are periodic in a periodic random process. If ...
23 views

### Spectral unfolding for Aubry-Andre model

While I was studying on random matrix theory recently, I have tried to unfold the spectrum of Aubry-Andre model. If the amplitude $\lambda$ of quasiperiodic onsite potential is less than 2, then it is ...
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### Considering the deterministic nature of the macro/Newtonian world, how does branching in MWI cause so vastly different macro states?

Given that branching occurs at such a minute scale, how do we come up saying “in this world I’m having pizza today, in another curry” or something similar if changes at the quantum state are averaged ...
578 views

### How is the randomness of single atom radioactive decay verified experimentally?

What experimental setups and statistical tests are used to empirically verify that the decay of a single atom cannot be predicted, it is truly random the decay of a single atom is not influenced by ...
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1 vote
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### Second order brownian motion $\ddot{x}(t) = \xi(t)$

I'd like to solve for the pdf of position $$P(x,t) = \Big\langle \delta\Big(x-\int_0^t dt_1 \int_0^{t_1}dt_2 \xi(t_2)\Big)\Big\rangle$$ for the second order Brownian motion given by a Langevin-type ...
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### How can one distinguish between a random process and a chaotic process? [duplicate]

Chaos is not a random process, although it may look like one. If I am given a set of observations, is it possible to determine if the observations are generated by a random process or if they are ...
1 vote
34 views

### PDF for zero point of random function

Let us suppose a complex random function $\displaystyle \Psi (\mathbf{x})$ and its complex conjugate $\displaystyle \Psi ^{*}(\mathbf{x})$. We assume that these functions possess gaussian statistics, ...
44 views

### Could an external being predict quantum uncertainty given all the information of our Universe? [duplicate]

I'll elaborate and be more specific. I understand that this is almost a metaphysical question but nonetheless I want to give it a try. Could an external being outside our Universe create 10 ...
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### Why is entropy of gas reamains constant during adiabatic expansion?

In adiabatic compression, we add energy to the gas via piston and decrease volume. Now the increase in energy and decrease in volume will cause increase and decrease in entropy respectively, but it ...
1 vote
584 views

### What factors affect the rate of decay of a radioactive atom? [duplicate]

I saw a specific quote that made me question this : "Other atoms in the universe don't influence the rate, it's just an intrinsic property of each separate atom that it has some chance to decay.&...
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1 vote
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### Mysterious path integral divergence after Hubbard-Stratonovich transformation

Let us consider common gaussian path integral over some complex random field $\displaystyle \Psi (\mathbf{r})$: \begin{equation*} N=\int D\Psi ^{*} D\Psi \ \exp\left( -\int d^{n} r\ \Psi ^{*}\hat{K} \...
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### How much do quantum fluctuations affect our lives? [closed]

In other words, how deterministic is our daily lives given the probabilistic attributes of quantum mechanics? How much does the randomness of quantum mechanics affect our thoughts and our actions? To ...
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### Could quantum world be deterministic even though there would be no hidden variables at play?

To my knowledge it is quite widely accepted in the scientific community that at the quantum level physics is not deterministic, only probabilistic. I know that there were some efforts to find some ...
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### What is the probability distribution for the detection times of radioactive emissions from a radioactive sample?

Assume I have a radioactive sample composed of $N$ atoms of some type A. I know that if I measure at time t the number of atoms not already decayed, this number will be given by  N(t) = N_0 \exp^{-t/...
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### Can you have an overall probabilistic many body quantum system with deterministic body mechanics but probabilistic interaction mechanics among them?

I try to understand if it is possible a quantum many body system in total to have a probabilistic time independent behavior (not stochastic which has a time-depended evolution) but with its elements (...
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### Is consciousness likely to be a result of chaotic, or random processes? [closed]

Given that just about everything in the universe at a non quantum level is deterministic, what does this say about free will and consciousness? Are these likely to be a result of randomness at the ...
1 vote
81 views

### If there is a randomness to the polarization of photons (Bell's Theorem) why radio signals hit the reciever in the same state they left the emitter? [closed]

I have tried to understand Bell's Theorem (and I am still working on that) and I am probably missing something here, but a radio signal does not seem very random, rather the opposite. It seems very ...
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215 views

### Is the Timing of Alpha Particle Radiation Perfectly Random?

Suppose one has a single atom of a radioactive isotope that radiates an Alpha particle. I'll accept that the timing of when that Alpha particle radiates is completely random, when the atom is ...
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1 vote
48 views

### Probabilities for quantum random number generators

Consider a quantum random number generator (QRNG) X, which generates integers at random. (Apparently, due to quantum statistical properties, this type of generation is truly at random, see e.g. "...
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### Randomness in parallel universes [closed]

Suppose we have two completely identical universes (for instance in Tegmark's type III multiverse). In both of them, two identical men are sitting behind identical random number generators (RAN1 and ...
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### Classical unpredictability

Consider, a box with $N$ particles each of mass $m$, arranged at time $t=0$ to be moving parallel to the $x$-direction, with mean velocity v and mean distance l. The particles are spheres of mean ...
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### Feynman's random walk (6-3)

How does Feynman get to $D^2_{N-1}$? The expected value of $D^2_N$ for $N>1$ can be obtained from $D_{N−1}$. If, after $N−1$ steps, we have $D_{N−1}$, then after $N$ steps we have $D_N=D_{N−1}+1$ ...
5k views

### Why does a collection of radioactive atoms show predictable behaviour while a single one is highly random?

Well, we know that it is impossible to say exactly when a radioactive atom will go on decay. It is a random process. My question is why then a collection of them decays in a predictable nature (...
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369 views

### Fundamentally random physical phenomena

I read on Wikipedia: Quantum mechanics predicts that certain physical phenomena, such as the nuclear decay of atoms, are fundamentally random and cannot, in principle, be predicted. What does that ...
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### How does quantum theory allow a rock to turn suddenly into a duck? [closed]

Quantum theory does not allow a rock to turn suddenly into a duck. It does not allow any other bizarre transformation to happen either. This idea is a myth perpetuated by people who misunderstand ...
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### Applications of the Gaussian unitary ensemble

It is well known that the pair correlation function of the zeros of the Riemann zeta function reproduces the correlation function of the random matrices from the Gaussian unitary ensemble (GUE). ...
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### Quantum: Is it possible to determine the past knowing the present?

Due to quantum randomicity, it's impossible to determine the future knowing the present. But is it possible to determine the past knowing the present? As far as I understand, it is impossible because ...
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### Why do chaotic numbers improve evolutionary algorithms such as genetic algorithm?

I have implemented a genetic algorithm to solve a problem. In the process of genetic algorithm, instead of random numbers, I have used the chaotic numbers generated by the logistics map. The genetic ...
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### What is the reason that Quantum Mechanics is random?

We know quantum mechanics gives a random result when we observe a particle that's in a superposition, but why is it random? One of the explanations I've heard is that because light comes with those ...
239 views

### What is a probabilistic physical theory?

What do we mean when we say that we have a probabilistic theory of some phenomenon? Of course, we know from experience that probabilistic theories "work", in the sense that they can (somehow)...
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