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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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163 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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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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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
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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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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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259 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
57 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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207 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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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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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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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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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 ...
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Schrodinger's “What is life ” book quote: : The laws of physics are statistical in nature [closed]

In the book What is life? by Erwin Schrodinger, he says that the laws of physics are statistical in nature. Today, thanks to the ingenious work of biologists, mainly of geneticists, during ...
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When exactly is “God playing dice”? (Question on Hamiltonian and ground state, actually)

There is something I don't get: So I read that by applying an operator to the wavefunction (aka. measuring stuff), it is as if the wavefunction collapses onto one defined state which is an eigenstate....
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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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How does one understand the connection between symmetry and randomness?

In this famous book Physics from symmetry the author Jakob Schwichtenberg tells us all the existing physics can be derived by the symmetry of nature.In my opinion, the intuitive thing I can recall ...
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What is the minimal discrete model of wave propagations?

If one takes the step size of an $n$-dimensional symmetric random walk to be infinitesimal, then the transition probability becomes the heat kernel. Thus, symmetric random walks are discrete, or ...
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Difference between “Random motion” and “Brownian motion”?

I know "Random motion" is non-deterministic unpredictable motion of a particle. But it seems "Brownian motion" has some form of determinism as we can predict the pattern created by path taken by ...
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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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1answer
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Can quantum computer provide random or just pseudo-random number, or none of both? [closed]

Can quantum computer provide random or just pseudo-random number, or none of both? It's a bit confusing me, since collapse of wave function once measured.
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1answer
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Feynman's random walk: How does he get $⟨D^2_N⟩=N$?

In Feynman's lectures, section 6.3, I follow most of his argument about a random walk, but I miss one step. To summarize, he's discussing a one-dimensional random walk (eg, determined by coin flips), ...
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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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Is the momentum of a particle both uncertain and, independently, also random?

Is momentum of a particle "random" because it is uncertain, or is it uncertain in addition to being random? Is the uncertainty principle and quantum randomness different names the same physical ...
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3answers
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Is there a mechanism for randomness?

I couldn't think where to post this, so I decided physics is the closest to answering this. Apologies for my amateur understanding of QM (0 understanding of QFT), I learn on free time by internet, so ...
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“Randomness” versus “uncertainty”

Highly rated PhysicsSE contributor @CuriousOne regularly makes the following claim about quantum mechanics (e.g. here): There is no randomness in quantum mechanics, there is only uncertainty. I ...
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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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What would happen if you went back in time to get a random number?

For example, you go to a website that generates a random number. You get the number 8. What would happen if you went back in time a few minutes, and repeated the same actions. Would you get the same ...
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Could the randomness of quantum mechanics be the result of unseen factors? [duplicate]

The possibility of randomness in physics doesnt particularly bother me, but contemplating the possibility that quarks might be made up of something even smaller, just in general, leads me to think ...
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1answer
565 views

What does it mean that an electron's position is described by probability?

I just read an answer to a Phys.SE question about why electrons don't collide with protons where an answering user said: In quantum mechanics, an electron doesn't have a definite position or ...
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1answer
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What is randomness? Can we simulate randomness? [closed]

I came across a computing function which gave me random output from a group of numbers. I've asked this question on StackOverflow. Do we really understand what is randomness? We can calculate ...
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454 views

Why is a random walk's RMS distance from the starting position$\propto\sqrt{N}$? [closed]

Why is the root mean squared (RMS) distance from the starting position of a (1D, 2D, or 3D) random walk of $N$ equally-sized steps proportional to $\sqrt{N}$? Is it also$\propto\sqrt{N}$ for $n$-...
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Randomness v. complexity

There are a few other topics I found that explore this idea from a different perspective: Is randomness deterministic? Can randomness exist? Is the universe fundamentally deterministic? My question ...
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5answers
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Could the universe be accurately simulated with an infinitely powerful computer? [duplicate]

This would mean that every event happens because of what has hapened before it and there is no randomness factor. At a microscopic level, the motion of atoms is a result of the motion of other atoms ...
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1answer
414 views

Examples of “Random Access” in real world [closed]

In a Random Access Memory (RAM) an index (usually represented in binary) is used to access a location of memory and retrieve/store a value. Are there natural physics processes, interactions, ...
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2answers
876 views

Does quantum randomness measurably affect macro-sized objects?

I understand that while it is believed that there is no true randomness on the macro scale, there is true randomness on the quantum scale. A previous theory that quantum processes could be determined ...
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1answer
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What exactly is entropy? Why is it measure of randomness? [duplicate]

What exactly is entropy? Why is it measure of randomness? I have been told Entropy is measure of randomness and it increases everytime randomness increases. What is Randomness? Randomness in what? ...
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4answers
511 views

Is there a mathematical basis for Born rule?

Wave function determines complex amplitudes to possible measurement outcomes. The Born Rule states that the probability of obtaining some measurement outcome is equal to the square of the ...
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1answer
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Is there $\frac{1}{f^{0.5}}$ noise?

I've heard of $\frac{1}{f^0}$ noise (white noise), $\frac{1}{f}$ (pink, or sometimes tan noise), and $\frac{1}{f^2}$ (brown noise). But why no $\frac{1}{f^{0.5}}$ or $\frac{1}{f^{\pi-2}}$ noise. Do ...
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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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1answer
189 views

Does the randomness of QM do much in everyday life? How much? [closed]

My apologies if in its current state this question isn't squarely suited here; I've worked it until it seemed reasonably articulate. Feel free to move it if it'd be better received elsewhere. ...
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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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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
459 views

How random is a lottery machine? What conditions would make it less random?

Professional lottery machines like this one are accepted as producing genuinely random results. (Or random enough?). However, it seems like the results are a largely a product of Newtonian ...
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1answer
485 views

Half wave plate in front of polarising beam splitter?

I have seen (in e.g. quantum random number generators) a half wave plate in front of a polarising beam splitter. But why do we need it and what would be different if we did not have it?
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529 views

True randomness? [duplicate]

I am a physics high-school student so my knowledge is not very deep on the subject. We started learnning about quantum mechanics and on some processes that my teacher described as random. I began to ...
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Why do all the atoms of a radioactive substance not decay at the same time?

Why does the substance decay at a rate which is proportional to the amount of the substance at that moment? As all atoms are in hurry to become a stable atom and as their decay do not depend on any ...
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How do particles “know” when to decay?

So, as I understand it, in a substance that is made of radioactive elements, the half-life tells us how long until the half of those atoms decay into their next atom [is there a name for that: the ...
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1answer
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Fourier transform of random variables

My question is concerning Fourier transforms of random variables. So if the question itself is too heavy a task but you know of any good resources to learn this topic that would also be very much ...
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1answer
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True randomness via Radioactive decay [duplicate]

Is radioactive decay able to be used for true randomness? And do we know if radioactive decay is truly random? Edit. Here is a example true random number generator made using radioactive decay. http:/...