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Discrete means as opposed to continuous. For, instance, people may ask questions about discrete electric charges, discrete spacetime, discrete energies, etc. If discretization is vital/essential to the question then tag it with the [tag:discrete] tag.

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Representing a system of particles being mapped from two to three space [duplicate]

Let's say you have a grid with nodes at the intersections of the grid which represent particles. Noether's theorem says that any differentiable symmetry of the action of a physical system has a ...
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1answer
31 views

What is a finite cellular automaton?

I found this paper: https://arxiv.org/abs/1606.08764 There, it is said "We realize constant-space quantum computation by measure-many two-way quantum finite automata" What are "finite automata"? ...
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73 views

Is simulating quantum field theoretical equations in the continuous limit the same as simulating really quantum continuous processes?

At the end of this article: https://hal.archives-ouvertes.fr/hal-00542373/document it is said that: "For example, several works simulate quantum field theoretical equations in the continuous limit of ...
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59 views

Are there any proved consistent quantum continuous cellular automata/game of life model?

There are quantum cellular automata (continuous game of life, which is a type of cellular automata): https://hal.archives-ouvertes.fr/hal-00542373/document There are continuous cellular automata (...
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1answer
66 views

Mechanism for light generation

Is all observable light caused by electrons dropping to a lower discrete energy level while bound in an atom? If so, how can a continuum of frequencies be generated? Is the thermal radiation ...
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3answers
114 views

Quantum mechanics calculations - must they always output a rational number?

If space is quantized, and particles are quantized, then the chance of a particle showing up in a specific unit of space must be a rational fraction? Could a quantum mechanics calculation ever output ...
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62 views

Is the universe a lattice?

My understanding is that cause and effect create a partial order of events in the universe (and that relatively prevents anything stronger). My understanding is also that it’s generally useless to ...
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2answers
39 views

Quantisation of States in QM

In the orthodox interpretation, the eigenvalues are the only measurable values of the corresponding operation, i.e., if the total energy of a particle is measured, the only numbers (as outcomes) are ...
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3answers
113 views

Is there a basic/elementary mass in the universe? [duplicate]

When speaking about electrical charges, it seems every particle either has a charge $+1$ or $-1$, in units of the electron charge. Therefore, we have a fundamental charge. But what about mass? Is ...
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47 views

Why is $x(t) = \frac {x_n + x_{n+1}}{2}$ when proving the Euler-Lagrange Equation?

When proving the Euler-Lagrange Equation for a single degree of freedom, we replace continuous time with stroboscopic time. We replace $$\dot x=\frac{x_{n+1}-x_n}{\Delta t}$$ but why do we replace $$...
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0answers
15 views

How to obtain boundary effects in the eigenmode analysis of a discretized WLC?

I'm currently working on the eigenmodes of a worm-like chain (WLC) polymer in the discretized version. We have the overdamped Langevin equation $\zeta\dot{r}(s,t)=-\kappa r''''(s,t)+\xi(s,t)$ for a ...
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29 views

Why are physical systems continuous?

To my (very limited) knowledge, physical systems (fluids, for example) can't have jump discontinuities. Why? Which fundamental laws can this be derived from, if any? This question is related to ...
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25 views

DFT of a non-continuous discrete time series

I am looking for a periodic signal in a time series $x_i, \quad i=1, \, ...,\, N-1 , \, N , \, N+P , \, N+P+1 , \, ... , \, N+P+M$ where $P$ is an unkwnown gap in time, for which I have no ...
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1answer
58 views

Is light a discrete or continuous phenomena?

Image a light bulb. In it the filament with a simple metallic composition, copper or other metals. At the precise instant, say $t=0$, where the first copper atom will be shining. In which direction ...
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0answers
14 views

What about space, what can we assume [duplicate]

Keeping it simple, is space infinitely divisible? Of course I realize the answer is no simple task. Regardless, keep it simple enough that in a sense, a common understanding amongst the average person ...
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0answers
59 views

What are common methods to remove discretization on experimental measures?

I have some experimental data, and since the measurements are digital, the data is discretized/quantized/rounded/truncated. I need to know if there are general methods, or common methods, to "smooth" ...
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2answers
352 views

Feynman's path integral and energy discretization?

Feynman’s path integral formulation of quantum mechanics is based on the following two postulates: If an ideal measurement is performed to determine whether a particle has a path lying in a region of ...
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2answers
106 views

Path Integral analogue for discrete systems

What is the analogue for path integral formulation for a discrete system? e.g. chain of typical 2-level excitonic systems: \begin{equation} H=\sum_k \sigma^+_k\sigma^-_k+\sum_{k<l}(\sigma_k^+\...
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2answers
91 views

Is the space of possible positions of a particle in QM discrete?

I recently updated my understanding about quantum mechanics from popular science level to basic undergraduate level. What surprised me is that for the quantum state of a particle, the wave function ...
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1answer
132 views

Classical Mechanics: Continuous or Discrete universe? [duplicate]

The question of the "continuous" or "discrete" nature of the universe is the subject of diatribe among the greatest physicists in the world. I would like to discuss the same topic, but asking a ...
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1answer
129 views

How is particle in a ring is in bound state?

Particle in a potential well forms a bound state which gives rise to discrete energy levels. But states for particle in a ring also have discrete energy levels even where there is no potential well. ...
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1answer
101 views

Is space-time quantised? [duplicate]

i was reading and a question popped into my head and i could not find the answer anywhere if photon destruction is instantaneous doesn't it mean that space-time is quantised? here is my problem: ...
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2answers
130 views

Fourier Transform and Lattices

I've been always confused Fourier transforms on lattices because some times a continuous version is used and others a discrete version is used. I don't understand well when should use one or the other....
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1answer
50 views

Continuous limit of discrete position basis

Say we have a $1D$ lattice with spacing $a$ between two sites. How does one formally map the discrete position basis of the lattice to a continuous one in the limit $a\to 0$. For instance how does ...
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1answer
91 views

Is there a proposed minimum amount of energy?

I've read that "The Planck length is believed to be the shortest meaningful length (...)"(1). Regardless of the factual accuracy of this claim, I'm wondering if: is there a related concept regarding ...
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0answers
76 views

Planck length, planck time, and planck rotation? [duplicate]

given that there is a fastest speed at which anything can travel in our universe,299,792,458 meters per second, that seems to imply there may be a smallest distance in our universe, so first of all, ...
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0answers
64 views

Lorentz Symmetry Group as continuous symmetry for limit of discrete spacetime

There is a variety of models of quantum field theory, where discrete spacetime is used as technical support, or even suggested as physical reality. As far as I know, all of such models faced serious ...
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1answer
60 views

Do discrete symmetries in molecules leave statistical “artifacts” like the Equipartition Theorem?

In statistical mechanics we have the equipartition theorem which can derive heat capacity simply from degrees of freedom. For example, diatomic gases have an increase heat capacity of $ \frac{7}{2} N ...
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0answers
44 views

Is discrete energy spectrum a result of representing external systems as a potential?

A quantum harmonic oscillator, or a quantum model of the hydrogen atom, have discrete energy spectrum. However, both models involve a potential, which means that the system is not isolated. One could ...
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0answers
41 views

Relation of the Heat kernel and the solution of the discrete diffusion equation

As is well known, the solution to the continuous 1D diffusion equation $\partial_t f=D\,\partial_x^2 f$ is given by the Heat kernel $$f(x,t)=\frac{\mathrm{e}^{-x^2/4Dt}}{\sqrt{4\pi Dt}} \ .$$ On the ...
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0answers
19 views

How is energy quantized? [duplicate]

I'm at the moment studying quantum physics and I came across $$E=hf.$$ My question is: how come there are only certain energies allowed if in this formula $f$ can be any number, and therefore, energy ...
2
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2answers
116 views

Is $Y: (t,x,y,z)\to(t,x,-y,z)$ a Lorentz transformation?

A question from the book "Quantum Field Theory and the Standard Model" by Matthew D. Schwartz. Is the transformation $Y: (t,x,y,z)\to (t,x,-y,z)$ a Lorentz transformation? If so, why is it not ...
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0answers
32 views

Confusions in discretizing a momentum delta integral

I have an integral of the following form: $$\int dk_{x}dk_{y}dk_{z}\frac{1}{(2\pi)^{3}}\delta\left(\sqrt{k_{x}^{2}+k_{y}^{2}+k_{z}^{2}}-p\right)f(k)$$ There are two ways to convert it into discrete ...
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2answers
96 views

Is there a conserved quantity for Parity Symmetry?

I've recently read about the Cobalt-60 experiment and Parity violation on weak interactions, what says the parity is not a symmetry on weak interactions. But if I did not understand wrong EM and ...
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1answer
62 views

How can there be instantaneous rate of change? [duplicate]

To find rate of change you need two instants. how is the rate of change calculated at a particular instant when at least two instants are needed to find it?
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3answers
296 views

How does anything move through a physical distance? [duplicate]

I was wondering and came across a thought: if an object is moving at a particular speed, say 5 m/s, it is equivalent to say that the object is moving at 500 cm/s, or 5000 mm/s and so on; clearly, you ...
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0answers
9 views

How do we see the manifestation of energy quantization in Sch. Eqn.? [duplicate]

Just in general terms how does energy quantization manifest in solving the Sch. Eqn., in the cases like HO and Linear Potential, etc. I am only ask for a little bit of intuition.
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1answer
220 views

Is a magnetic monopole really necessary for charge quantization?

The usual remark that goes about in a first encounter of Dirac monopoles is that it solves the problem of electric charge quantization. I have also studied t'Hooft Polyakov monopoles which ...
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2answers
84 views

Why do we use differential equations in physics instead of $h$-difference ones?

Since we don't know whether space and time are discrete or continuous wouldn't it be a better idea to use $h$-difference equations where the derivative is $$f'(x) =\frac{f(x+h)-f(x)}{h},$$ since they ...
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1answer
74 views

Does Nielsen-Ninomiya theorem apply to quarks?

Does the Nielsen-Ninomiya theorem apply to quarks? Since quarks are massless before EWSB and left & right quarks have different weak hypercharge, there should be additional species of quarks when ...
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1answer
68 views

Discretization of the induction equation using the Finite Volume Method (FVM)

I am trying to discretize the induction equation using the finite volume method. The equation with the quasi-static assumption is given as $$( \mathbf{B} \cdot \nabla)\mathbf{u} - (\mathbf{u} \cdot \...
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1answer
87 views

Wing vibration discrete systems problem

I am trying to wrap my head around the energy terms that arise from the following discrete systems vibration problem: The potential energy terms seem simple enough. I include the elastic potential of ...
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3answers
2k views

What is “quantization”? Give one example [duplicate]

I just want to know the definition/explanation of quantization in layman's terms. Also an example would be very helpful if provided (not necessary).
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0answers
50 views

Bound state and discreteness

The solution of Schrodinger equation in finite square well gives discrete energies in the bound states, but the energy is not discrete in case of scattering state. What is the physical reason behind ...
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1answer
85 views

What is a space group?

I learned about space groups but never saw a definition of one. For example, the Wikipedia article Space group discusses space groups but doesn't say what a space group is.
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0answers
18 views

Quantisation of charge vs. Mass [duplicate]

Charge is quantised as we all know (e) it has one constant value. It is also said that quark model supports it also. Then what are difficulties in proposing quantisation of mass? I mean why it has ...
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1answer
255 views

Why is translation energy a continuum and not quantized?

When starting the study of quantum theory, usually the teacher separates the functions in electronic, vibrational, rotational and translational parts. As far as I know, we should solve Schrodinger ...
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2answers
67 views

Violating Quantization of Charge?

Isn't it the violation of "the quantization of charge" when we use $dQ$ for calculation like integration or derivation?
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3answers
137 views

Terminology: Meaning of a Quantum

When people say that a photon is a quantum of light, are they talking about 2 different types of quantizations in one phrase? To quantize something, you take something continuous and make it discrete (...
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22 views

Why continuous spectrum for matter in condensed state? [duplicate]

while going through Resnick's Quantum Physics(2nd edition), in section 1.2 I came across a statement: "Matter in a condensed state (i.e.,solid or liquid) emits a continuous spectrum of radiation." I ...