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.

learn more… | top users | synonyms

6
votes
1answer
408 views

Can universal continuity be experimentally falsified?

It is an unresolved question whether the universe is discrete or continuous in its intricate quantum level structure. See for example: Is the universe finite and discrete? How could spacetime become ...
3
votes
3answers
226 views

Is Bekenstein entropy limit inconsistent with universal continuity?

It is unknown whether the universe is discrete or continuous in its intricate quantum level structure. See for example: Can universal continuity be experimentally falsified? Is the universe finite ...
29
votes
8answers
5k views

Is (rest) mass quantized?

I learned today in class that photons and light are quantized. I also remember that electric charge is quantized as well. I was thinking about these implications, and I was wondering if (rest) mass ...
1
vote
1answer
168 views

Why is the density of states in $k$-space constant?

Why are the allowed states in $k$-space equidistant in every direction? As a consequence of this, the density of states for phonons in 3D is $$\frac{V}{(2\pi)^3}$$ while for electrons it is $$2 \frac{...
13
votes
2answers
533 views

Must bounded operators have normalisable eigenfunctions and discrete eigenvalues?

When we have bound states, to my knowledge, we have states that are normalisable and a discrete energy spectrum. However, in the case of scattering states that have a continuous energy spectrum, the ...
1
vote
1answer
194 views

Is there a minimum distance?

I would imagine there is no limit to how small space can get. Is this correct? I am aware of planck's constant, but cannot objects be closer than Planck's constant is short? Perhaps this question is ...
6
votes
2answers
130 views

Are there any true discontinuities in physics?

When we first learn physics, it's often presented very 'discontinuously'. For example, pop quantum likes to talk about objects being "either" particles or waves, leading to a lot of confused questions ...
1
vote
2answers
61 views

Energy Quantization

Why a free particle gives rise to Continuous Spectrum energy eigenvalues where particle in the Bound States provide the quantization?
2
votes
3answers
225 views

A universe of angular momentum?

I read this on Wikipedia: [...] That most tangible way of expressing the essence of quantum mechanics is that we live in a universe of quantized angular momentum and the Planck constant is the ...
0
votes
1answer
52 views

Representing Hamiltonian in discrete position basis

I am trying to numerically find eigenstates of an Hamiltonian. Let $V(x)$ be some potential. Suppose my space is between $-L,L$ and that the allowed positions are every $\Delta x$, such that $\frac{1}{...
1
vote
0answers
46 views

What is the cause of discrete or quantized energy levels in an atom? [duplicate]

I understand how it is that electrons move from one energy state to another, however I've not been able to find anywhere that describes why an atom has any particular states. Why should an atom of ...
2
votes
3answers
203 views
0
votes
1answer
62 views

Issues of normalization & differential final state momenta in analysis of normalized differential quantum-field-theoretic probability of scattering

The normalized differential quantum-field-theoretic probability $dP$ of scattering is given by $$dP=\frac{|\langle f |S|i\rangle|^{2}}{\langle f|f\rangle\langle i|i\rangle}d\Pi,$$ where $|i\rangle$ ...
0
votes
0answers
29 views

How much time a ball stays at rest when throw up?

You throw a ball straight up in the air. The ball attains its maximum height when it is momentarily at rest,(v=0). How mutch time is this moment? If we take time has continuous it is an infinitesimal ...
0
votes
2answers
50 views

Particle in a box, quantization of energy

I'm learning about how the energy of matter is quantized like how the energy of light is. My textbook illustrates the concept of quantization with the particle in a box: "A particle of mass $m$ ...
1
vote
0answers
47 views

I want to know about the quantization of mass [duplicate]

Is mass quantized? If yes, then why do we see all amounts of mass? Well , can it be said quantized just for smaller masses?
0
votes
0answers
43 views

Scale invariance

Physically why should scale invariance break down at the Planck limit? If not what are the other possibilities to save the quantum granularity of spacetime? I would really appreciate professional ...
2
votes
1answer
650 views

Is Space-Time Quantisation necessary or even meaningful?

It is believed among people working on Quantum Gravity, that space-time must be quantised at the Planck scale. Although it is very hard to verify such proposition, it is interesting from a ...
0
votes
1answer
41 views

What are all charge-like quantum numbers?

What are all charge-like quantum numbers? In particle physics there are often things (like charge conjugation) that apply to all charge like quantum numbers. Everytime I read something about charge-...
1
vote
1answer
105 views

Symbolic dynamics of a multidimensional system

Let $x_t = F(x_{t-1})$ be a discrete-time dynamical system in the chaotic regime. Starting from an initial condition $x_0$, we can generate a time series $(x_t)$ where $t =1,2,...,T$ indicates the ...
-2
votes
1answer
43 views

Doesn't modelling using Lie Groups assume spacetime is continuous?

Lie groups are used to some behaviors of quantum mechanics, as well as forming a basis for Kaluza-Klein, Yang-Mills, and String theory. But Lie groups are defined as involving a differentiable ...
2
votes
2answers
184 views

Mapping between numbers and symbolic representations

I am not a physicist but applying symbolic dynamics for information coding in signal processing. Is there any mapping between symbols and numbers?
1
vote
1answer
43 views

Why magnitudes can be quantized? [closed]

If charges and any other magnitude must be or well quantized by multiples of an integer, or simply discrete values. How could we us assign values to the quantized quantities?, beacuse If I measure ...
2
votes
0answers
50 views

Lenses that pixeliate incoming light [closed]

Is it possible to make a lens that 'pixelates' the light passing through it? I imagine a pair of glasses, that when put on, turn the world into a grid of discrete pixels, each having, or appearing to ...
0
votes
1answer
93 views

What came before quantum theory?

My professor explained today that the idea behind quantum theory is that particles have quantized energy states. To an undergrad like me, this is kind of strange. Wouldn't it always make sense that a ...
1
vote
1answer
22 views

Formation of Line Spectra in light of Bohr's Theory [closed]

I am reading about the electronic structure. It is written that when hydrogen's electron comes back to ground state from excited state, it releases energy in a specific amount according to Bohr. But ...
2
votes
6answers
358 views

Is nature quantized?

I was reading Planck's postulate the other day on Wikipedia and couldn't help but noticing the sentence: "...is the postulate that the energy of oscillators in a black body is quantized..." ...
0
votes
1answer
51 views

How is the range of $x\cdot s$ in Simon's algorithm restricted to $\{0,1\}$?

The final critical step of Simon's algorithm (before setting up a simpler system of equations to solve) involves taking advantage of the fact that $$x\cdot s \in\{0,1 \}$$ but for $x,s \in \{0,1\}^...
5
votes
1answer
131 views

How do we choose how to discretise spacetime in loop quantum gravity?

In LQG we choose a two-complex (or other) on which to discretise GR before quantising. I'm a little uncertain about the nature of this choice. Is the two-complex an a priori property of the universe (...
1
vote
1answer
109 views

Planck's Law. It's $E=hf$ or $E=nhf$?

My textbook provides intuition of Planck's Quantum theory which is copied right next. Max Planck proposed that emission or absorption of energy in a blackbody is discontinuous. It is absorbed or ...
1
vote
1answer
117 views

How does the discrete energies of alpha and gamma rays prove the existence of nuclear energy levels

I was reading up about Nuclear Energy Levels and came up with the aforementioned question. To me, there seems to be no direct connection between the two statements and therefore, I would like to know ...
0
votes
0answers
61 views

Scale factor of the universe

Do we impose that the scale factor $a(t)$ of the Universe is a continuous function? Or there is a physical meaning? Usually in physics we define functions to be continuous, such as the velocity of a ...
1
vote
1answer
100 views

Is there a simple way to explain quantised conductance? [closed]

I am biologist and I need to pass a nanotechnology class. I am stuck with this term of quantum resistance. Basically this appears to me as normal Ohm's law, except that takes into account Heisenberg ...
0
votes
1answer
45 views

Size of box vs. discrete-ness of state of the system

From Statistical Physics, 2nd Edition by F. Mandl, pg. 36: A sufficiently large box (say 10 light-years across) will clearly not affect the properties of our system, ion plus electron sitting ...
4
votes
2answers
220 views

Dirac magnetic monopoles and quark fractional electric charge quantization

When applying the Dirac quantization rule for electric and magnetic charge, I assume one is considering unit electric charges such as electrons. How does the Dirac quantization rule apply for the ...
4
votes
1answer
981 views

Dirac magnetic monopoles and electric charge quantization

Wikipedia describes how assuming the existence of a single magnetic monopole leads to electric charge quantization. But what if there's more than one? The same argument would apply to each of them ...
1
vote
1answer
79 views

What is cause of quantization of charge? [duplicate]

What is cause of quantization of charge? When we rub two objects only an integral number of electrons or charges can be transferred is this the reason? Why electron has the smallest possible charge? ...
3
votes
1answer
62 views

Is all energy quantised?

I'm wondering if all energy is quantized? Can a particle with kinetic energy have any value of kinetic energy or is kinetic energy also quantized? My reason for asking this is that if a particle is ...
1
vote
1answer
62 views

How is Zeno's Dichotomy Paradox resolved according to physics? [duplicate]

I always thought of quantum space and quantum time as a solution, but then i figured out that "quantum space-time" is not actually true(yet). I've also heard of the calculus approach and limits, but i ...
0
votes
1answer
60 views

What makes things move in a universe with blocktime? [closed]

In a universe with blocktime the past, present and future all exist at the same time. But what makes it appear that for example my body is going from one movement ...
0
votes
1answer
38 views

Decoupling of double discrete Fourier transform

I have a problem with a double Fourier transform I encountered: $$\sum_{j=1}^L \sum_{l=1}^L e^{-i\pi \frac{n_1}{L} (j+l)}e^{-i\pi \frac{n_2}{L} (j-l)}V(j-l)$$ where $n_1,n_2$ are integer. If the ...
1
vote
3answers
96 views

Energy equation in Quantum Mechanics

We know that total energy of the system is classically continuous, but in quantum mecanics (QM) it is quantised. My question is: How can we use the conservation of energy equation to derive ...
3
votes
0answers
44 views

Snyder's Lorentz invariant discrete space-time

Can theories which say space-time is fundamentally discrete be compatible with Lorentz invariance? And if the answer is yes, in what sense is space-time no longer continuous? I'm sure this has been ...
0
votes
1answer
31 views

Is the hypothesis “at some level, spacetime becomes discrete” falsifiable?

Suppose I conjectured that, at some length scale, spacetime was discretized into "cells", Minecraft-style. For simplicity, I guess let's say they're cubes with side length $n$. Presumably we can put ...
3
votes
1answer
137 views

Is the energy always discrete?

In the von Neumann axioms for quantum mechanics, the first postulate states that a quantum state is a vector in a separable Hilbert space. It means it is assumed the Hilbert space has a basis with at ...
0
votes
0answers
32 views

Is there a fundamental frequency of time? [duplicate]

Our eyes and brains can only perceive frequencies as individual frames up to some limit, after which we perceive the motion to be "continuous." Is there such a frequency of time? Along the same line,...
5
votes
0answers
137 views

If spacetime is discrete: what would space expansion mean? [closed]

How is space expansion explained in physical theories where spacetime is quantized? Discrete spacetime is claimed in some candidate theories of quantum gravity like loop quantum gravity and algebraic ...
0
votes
0answers
44 views

Angular momentum $J_z$, how do we get eigenvalue of $m\hbar$?

If we have angular orbital momentum for $z$-direction, we assume that for state $|j,m>$ that eigenvalue is $m\hbar$. Similarly for $J^2$, we assume $j(j+1)\hbar^2$ Can I get reference of ...
74
votes
10answers
13k views

Is time continuous or discrete?

While working on physical system simulation software, I noticed that I had implemented discrete time, which means that there was an update mechanism advancing the simulation for a fixed amount of time ...
2
votes
1answer
86 views

Does limiting to infinity violate laws of physics?

It is noteworthy that one cannot simply divide any length more than the Planck-length. If so, one cannot simply divide any volume more than the $(Planck-length)^3$. So if I want to find the limit of ...