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.
241 questions
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Why do random quantum circuits produce entanglement?
There's a lot of work done on random quantum circuits, and very often the story is that you start from a completely unentangled state, then random unitary gates act on it, and you generically end up ...
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Does nature work exclusively on the cause-effect principle?
Does nature work exclusively on the principle of cause-effect or are there situations in which the principle is violated?
Is randomness in probabilistic process truly fundamental or just a reflection ...
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Where can I find information about Random Processes's Characteristic Functionals and Volterra series?
At first, hi everyone.
I'm having difficulties looking for information about the so-called 'characteristic functional' of a random process.
What I know about this concept is what follows:
when you ...
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Clarification about random field energy in Imry-Ma argument
Consider the Ising model in $d$ dimensions with a random local magnetic field $H_i$:
$$
\mathcal{H} = -\frac{J}{2} \sum_{\langle i, j \rangle} S_i S_j - \sum_i H_i S_i
$$
where $\langle i, j \rangle$ ...
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How do 1-dimensional random walks correspond to different interpretations of stochastic integration?
Very short summary of my problem: I want to intuitively understand why/how random walks with "random barriers"/"random traps" correspond to the Itô/Hänggi-Klimontovich ...
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Why randomness taking a specific outcome at that time? [duplicate]
Im a 16 year old and this question stuck in my mind. I cant find apt answer.
Imagine we tossed a coin, we have 50-50% chance to get heads or tails. We say its random but truly we can predict the ...
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Phase transition of shift of energy level under small perturbation in random matrix theory
I'm a mathematician and I'm thinking about a question in random matrix theory.
Suppose $H_0$ is a $N\times N$ GUE random matrix (variance of each element is $\frac{1}{N}$). We consider a small ...
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Where is an electron "physically" in superposition? [duplicate]
According to simple Google search:
When an electron is in superposition, its different states can be
thought of as separate outcomes, each with a particular probability of
being observed. An electron ...
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Has anyone constructed an explicit hidden-variable theory that reproduces the predictions of quantum mechanics for two separated qubits?
Consider the Hilbert space
$$\mathcal{H} = \mathrm{span}\left( \{ |0\rangle\ |0\rangle, |0\rangle\ |1\rangle, |1\rangle\ |0\rangle, |1\rangle\ |1\rangle \} \right) \cong \mathbb{C}^4$$
of (pure) ...
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The source of random information in physics
In computer science, we can use the heat of a gas (or radiation, for example) to generate random noise. From them we can get a lot of random information. However, the question arises, where does this ...
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What is the quantum mechanical root of causality?
Consider the following 3 premises.
Premise 1) Quantum mechanics has an inherent randomness.
Premise 2) Objects in the world appear to obey causality. For example, I can push a book on a table, and it ...
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Microscopic level randomness [closed]
I have a fairly simple question but can't find any clear answer anywhere it seems.
Let's say you would isolate an unstable nucleus and just wait for it to decay. You would know of the decay by having ...
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System size scaling of sums of random lognormal variables
I will not go too much into details, but my question may be summarized as follows:
Suppose you have a system of size $N$ and two lognormal-distributed random variables $A$ and $B$ associated with said ...
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How can events on the quantum-level be random but not on the macro-level? [closed]
This question has been asked before on PSE, many times, and I have looked at them. But I don't think any of them get to the crux of my question.
My chair is made up of quindecillions of atoms (not ...
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Is power spectrum a sufficient condition for determining autocorrelation function via Wiener–Khinchin theorem?
For an optical source with power spectrum as 𝐼(𝜔), the autocorrelation function is related to power by a Fourier relation (Wiener–Khinchin theorem).
F{𝑔(𝜏)} = 𝐼(𝜔)
However, the above relation ...
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Quantum: Which improbable macroscopic events are possible?
Basically, the title. Web search had not found pages in top results with similar QA.
E.g. I understand nuclear blast can just end at any time because random chain-reaction has probability of not ...
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Asymptotic form of solution to biased random walk
(Cross post from math.stackexchange)
Consider a continuous time biased random walk on a 1D lattice. The random walker walks with rate $k_\mathrm{R}$ to the right and with rate $k_\mathrm{L}$ to the ...
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Anderson localization in the continuum case
I haven't looked into Anderson localization before. A quick review of the available information gives the impression that this phenomenon has mainly been studied for the case of a discrete random ...
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Is the collision in LHC quantum mechanically so we cannot predict the trajectory?
I'm puzzled as always. In the LHC 2 streams of particles are accelerated in opposite direction and allowed to smash against each other in a controlled accident, then is it classical or quantum ...
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Why aren't completely random quantum states 'physical'?
I've come across the statement that 'completely random states are generically not 'physical', in the sense that they cannot be eigenstates of Hamiltonians with local interactions (in 1D)'.
Reference: ...
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Various types of correlation functions in models with random interactions
In the Ising model, spin correlations are characterized by the following correlation function
$$
C_{ij} = \langle \sigma_i\sigma_j\rangle - \langle \sigma_i\rangle\langle \sigma_j\rangle
$$
where $\...
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What is really meant by randomness in quantum physics [closed]
I don't really know if my question even makes sense but, we know that for the double slit experiment, there is no way possible of telling which slit the electron will pass, prior to observing. Does ...
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How do I compute the bounds of random walk for a given ellapsed time?
I am trying to model random walk of a gyro, given some manufacturer specifications of maximum random walk in units of degrees per root-hour.
My first step was to generate white noise with a standard ...
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Error analysis for counting experiments
i am trying to refresh my knowledge in error analysis and stumbled over an interesting question.
Suppose i have a radioactive compound and i want to measure the standard deviation of the decay count. ...
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Is randomness in quantum physics adequately formulated?
According to most experts' interpretations of quantum physics, some quantum event outcomes are random; they are not part of any cause-and-effect chain.
I'm struggling to find a thorough definition of ...
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Is Quantum randomness true randomness? [closed]
I would like you guys to read it, and see whether it makes sense, and correct me if anything is wrong.
I'm not an expert on these topics, so I understand if very wrong. It would be wonderful if you ...
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Is the universe deterministic, random, or both? [duplicate]
It occurred to me that the limits of possibility to the nature of the universe is it is either deterministic ie we are all at the will of natural laws that determine the outcome of events from the ...
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Is the random current model tight (in the sense of probability)?
Let us consider the random current model (of the classical Ising model) on $\mathbb{Z}^d$. More specifically, we have probability measures $\mathbb{P}_L$ on the product space $\mathbb{N}^{E_L}$ where $...
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Does the bias in a loaded die depend on gravity?
Suppose I bias a cubic plastic die by incorporating a lead pellet hidden just behind the '1' face, so that the probability $P_6$ of rolling a 6 is greater than the symmetric 1/6. Its exact behaviour ...
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Scientific determinism and the Heisenberg's uncertainty principle
I'm reading Brief Answers to the Big Questions by Stephen Hawking. In chapter 4, it discusses whether we can predict the future. As many have known that Laplace put forth that if we knew the positions ...
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Is Brownian motion truly random?
We say that Brownian motion is caused by the random collisions of particles. But let's consider an ionized gas; in that case, there's a nonzero net charge on the atom. Doesn't this mean the ...
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How accuratley can you determine the number of matchsticks in a matchbox from the sound it makes when you shake it?
This question is part of the International Physics Tournament 2023. The entire problem statement reads : How accurately can you determine the number of matchsticks in a matchbox from the sound it ...
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True Randomness/unpredictability in infinite quantum coin toss sequences?
In Comments on indeterminism and undecidability the abstract reads:
"In a recent paper 1, it has been claimed that the outcomes of a quantum coin toss which is idealized as an infinite binary ...
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Do random events really exist? [closed]
To highly clarify my question, let me define what I mean by a random event: "the event e is random, if and only if by having all the data about an event e, we cannot predict the consequences of ...
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Geiger tube counts-per-minute Poissonian, but counts-per-hour not. Why?
I am testing a Geiger tube and counting its pulses. Because the pulses are random, I expect the counts-per-minute (cpm) to follow a Poisson distribution. That's indeed what I found:
mean cpm = 38.39
...
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The Physical Meaning of Variance of Random Matrix Entries
I am trying to make some physical sense of the Hamiltonian described on pages 1, 2 here. The part I don't get is in the image attached below. I understand what the variance of each entry term tells me ...
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Sufficient and necessary conditions on random walk to obtain standard diffusion equation
In the simplest random walk model that is generally considered, the probability of the finding the particle at time $t$ in $x$, $P(x,t)$ is given by,
$$
P(x,t) = \frac{1}{2}\big[ P(x-a, t-\tau) + P(x+...
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Is the cosmic background radiation random and Kolmogorov complexity
In the article https://arxiv.org/pdf/physics/0510102.pdf the idea arises that if there was a Creator of the Universe and wanted to send us a message, then the "right" place to do it, would ...
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Per Newtonian mechanics, a coin toss exhibits deterministic chaos theory, but could relativity cause a probabilistic outcome of a coin toss?
It took me a long time to accept that a coin toss boils down to deterministic chaos theory. For example, the typical near 50/50 odds for outcomes of heads or tails results from complex initial ...
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How can randomness occur in the case of radioactive decay ? Isn't there supposed to be a rule for everything that's driven by a non conscious mind? [duplicate]
I'm not trying to be unscientific here but i cannot wrap this around my head that scientifically anything can work randomly except a conscious mind which is capable of making a random decision. how ...
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Does a random number generator have real entropy?
In thermodynamics, entropy is defined for gases. Of course, my laptop is not a gas. However, it contains a random number generator and I have seen the word ‘entropy’ being used in this context. Is ...
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Is there any paper/experiment on the deterministic behavior of coin-tossing?
I do not have background in Physics but Statistics. I am working on a small project on philosophy of probabilistic modeling.
Of course, we often model coin-tossing as if it comes from a Bernoulli ...
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Does the human brain use random number generators? [duplicate]
Neurons fire depending on the impulses they get from other neurons. This seems to be 'deterministic'. However, sometimes it might be useful to use random processes instead. Does the human brain have ...
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Conditional and unconditional interpretations of mean inter-collision times
This question appeared in a study guide for my graduate level written exam in physics. (It may have been the one from the University of Chicago.) I see that a similar question was asked here What is ...
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Kramers' Degeneracy and Geometric Symmetries
I am currently reading the third edition of 'Quantum Signatures of Chaos' by Fritz Haake and trying to work through section 2.7 (Titled "Kramers' Degeneracy and Geometric Symmetries"). I am ...
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Does quantum decoherence desctibe a deterministic universe?
QM describes a system, whose state evolve unitarily, which is deterministic. The apparent non-determinism comes from the measurement problem, where the state is projected to some subspace in a ...
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Is the randomness generated by quantum phenomena measurably better than the randomness generated by the best computational algorithms?
I am aware that quantum phenomena can be used to generate random sequences of numbers. Are such sequences measurably better than the random sequences generated by the best computational algorithms? ...
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Questions about the intuition on or physical meaning of probability space, random number, and stochastic process
I have a question about the physical meaning of, or the mathematical intuition on, the mathematical concept of probability space, random number, and stochastic process. Mainly, I would like to ask ...
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Is randomness in the collapse of the wavefunction in quantum mechanics simply a manifestation of chaos, and not inherently random at all?
Chaos is sensitivity to initial conditions. Could the randomness in quantum mechanics simply be a manifestation of chaos? The initial conditions would be both the initial state of a particle, and ...
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Information content needed to predict a physical coin flip perfectly [closed]
Let's just take a typical coin flip where a person flips the coin off their finger into the air (some reasonable distance, say 30-40 cm or so), catches it, and opens their hand to reveal one side face ...
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