Quantum physics Definition and 729 Threads

Would it always be identical? Would it ever be identical? Essentially with the current state of physics and taking quantum fluctuations into consideration, would it always be the same? Is there motion at T=0?Another question: If we restarted the Universe from the big bang and let it play out...

I've been relying on Wikipedia and some other questionable sources for a basic understanding of these studies, and i don't think I should rely fully on these sources. If anyone can point me to a place that is reliable I would greatly appreciate it.

Hey! I wanted to prove that: $$ P_L \bar{ \psi } = \bar{ \psi } P_R $$ And I want to know if I did it correctly. $$ --- $$ Here is what I did: $$ P_L \bar{ \psi } = \frac{ ( 1 - \gamma_5 ) }{2} \psi^{ \dagger } \gamma_0, $$ $$ = \frac{ 1 }{2} \psi^{ \dagger } \gamma_0 - \frac{ 1 }{2} \gamma_5...

As the title says, I am a mathematics major, but I'm taking extra physics and engineering courses. I'm interested in mathematical physics work in the future. I'm taking the first of two semesters of quantum physics offered by my school right now. I was planning to take the next course in the...

Hi, I'm currently in high school but I know several university maths and physics (just a little) I want to know about Maths: Lagrangian and Hamiltonian Fourier Transform (I self-studied Fourier series) Differential Equations (only know one way to solve them, I think its the most basic one)...

I'm very new to the understanding of Hawking Radiation. I don't know much about this theory, but I do know that Hawking radiation works on a Quantum scale. I know that with black holes this theory proposes th idea that over time black hole lose mass because of "Spontaneous appearing positive and...

In quantum physics we don't describe the trajectories of particles is that because it is just the description or is it because there is no more fundamental way to do it ? Could we say that the fact we don't know the intermediate position change the result ?

Homework Statement "Sometimes the idea of the quantum is compared to the units we use for money. A dollar can be divided into smaller units, where the cent is the smallest possible unit. How is this analogy incorrect? Homework Equations E=nhf The Attempt at a Solution My thought is that...

The results of the double slit experiment lead to the conclusion that a photon travels as a wave. Question 1: Is it possible to track the journey of the photon? It seems to me (correct me if I'm wrong) that from the moment we release the photon till contact with the detector we don't know what...

Can someone give me a brief overview of QCD, I'd like to know famous physicists that worked in the field, the main theory's it includes, when did it begin and why do we study it? Thank you.

Hello, As per the title - my name is Nick. I am soon to enter my senior year of high school. I come here partly due to recommendation of my teacher. This year, my plan is to participate in my city's annual science and engineering competition, which is connected to the Intel International...

I think it could be useful to have a thread where we can collect links to very practical material on quantum physics. For the start, I would like to give the link to the wikipedia page on Common integrals in quantum field theory...

I read that when heat passes through the glass of a greenhouse it gets absorbed by the Earth inside the greenhouse. The Earth reflects this heat but these rays are of longer wavelength so it bounces off the glass and inturn heats the greenhouse more. Now the heat coming from the sun is...

Why is/are an electron/electrons a sphere/spheres ? Need the mathematical proof...

For example, let's say that psi(q) is the wave function of an electron(which describes/represents the electron) that is located in an atom and isolated/unentangled from the rest of the system. What is the wave function value of this psi(q) ? What is the wave function for that whole atom(with...

(Hope this is the right forum) For my year 12 physics EEI (extended experimental investigation) basically a report. I was hoping to find a suitable quantum mechanics experiment that i could conduct. Does anyone know of an experiment like this? Thanks in advance

This might be a silly question but when people say that something on the quantum level is completely "random," (except for general probability) does that mean, according to theory at least, if you were to go back in time and repeat an experiment exactly that the results could just as easily be...

So... My question is quite simple. If i took an electron from an atom and put it in th palm of my hand (the electron has absolutely no kinetic or potential energy in this case, its resting), before i close my hand it will be there, but when i close my hand it might not. Am i right?

this is probably not appropriate but i don't know where to ask. if classical physics was correct then everything would be predestined and we have no free will. quantum physics merely added "randomness" to it, our thoughts are not chaotic and random. can someone explain how this randomness can...

Hello I am an incoming Biology student (college), i really wanted to take applied physics as my course but my parents told me that it is better to be a doctor, anyways, it's summer here and I started taking Calculus 1 in coursera.com (i have NO backgroud in calculus because we don't have...

Homework Statement What is the approximate transmission probability (in %) of an electron with total energy 1.524 eV through a barrier of thickness 343 pm, and a potential height of 2.654 eV? (Does it matter what the potential energy is before and after the barrier? Not really, as long as it is...

Reading about the concept of 'information' in physics, I have often read the Shannon definition of information contents, i.e. how compressible the description of something is. A truly random number can not be expressed in any shorter way than itself, thus having a high information contents...

Hello everybody, This first post is intended, as requested, as a small self presentation. I'm an italian electronic engineer, a programmer for job and a passionate in Quantum Physics and Physics (and Mathematics) in general. I live and work in Padua. I've almost finished to follow a series of...

What is more fundamental and why, the postulated time symmetry of QM tie evolution or the time asymmetry of the CPT theorem?

THE “INTELLIGENCE” BEHIND QUANTUM PHYSICS If the nature of quantum mechanics is that an observer affects the end “collapsed” state of a particle, than what constitutes a state of observation. The the only thing I can come up with that seems to determine what constitutes a form of observation is...

∫-∞∞(e(-x2)/(x02)) dx =π0.5x0 How do you get this? Sorry my math sucks.

Hi, I've been self studying physics for a few years and I'm looking for some new books, specifically on Quantum Mechanics or Quantum Chemistry. It doesn't matter if they are PDF files or actual books, and price doesn't really matter. I've read Feynmans Lectures books and I'm looking for the next...

Is quantum physics closer to the truth than classical physics, or is it just a different way of looking at the same problem? For example, the rules of baseball explain the behavior of baseball players better than the rules of football, and vice versa. The rules of these two sports are not...

What would happen if there was a supernova explosion near a black hole ? Would it just sit there and absorb all the energy incident on it ? Or would it simply vaporize into elementary particles ? And if it does vaporize, could the remnants give us a clue as to the quantum state of matter inside...

Why does the magnitude of a ket vector not matter? The motivation appears to be that a state vector only can decribe a particle, or no particle. But why shouldn't the magnitude of ket vectors not be used to represent the density of the particles, the average number of particles? I'm am fairly...

Does "Entropy" play a role in Quantum Physics?

Hello. I am in desperate need for advice. I have searched for advice everywhere and each time failed to obtain it. This is my last resort. Please help me and bare with me while I explain the problem. I am 28 years old guy. I have literally whole day free to pursue whatever goals I see fit...

Can basic quantum physics explain all of the traits of the tardis other than the consciousness and living metal?

Homework Statement Following gaussian wave packet: ## \psi (x)= \frac{1}{\sqrt{\sqrt{\pi a^2}}} e^{-\frac{x^2}{2a^2}}## Prove that this function is normalized. Homework Equations ## \int_{- \infty}^{\infty} |\psi (x)|^2 dx = 1## The Attempt at a Solution Is ## \frac{1}{\sqrt{\sqrt{\pi a^2}}}...

Homework Statement consider a particle at an interval ##[-L/2, L/2]##, described by the wave function ## \psi (x,t)= \frac{1}{\sqrt{L}}e^{i(kx-wt)}## a) Calculate the probability density ##\rho (x,t) ## and the current density ## j(x,t)## of the particle b) How can you express ## j(x,t)## as a...

In QFM, what does it mean to say that an electron is just an excitation of the electron field? Does this apply to all particles? Does it mean to say that an electron is the quanta of the electron field?

Hello, This is more a question about history of science in general. During my lectures on statistical physics, I noticed that some of the problems that Bolztmann faced lead to the introduction of: ##h/2\pi## (to introduce the unit of an action leading to a "unitless" partition function) which...

Hello, I'm Lachlan Pearce and love physics (mostly special relativity, astrophysics, and a little of quantum physics). If anyone wants to discuss any of this I'd be happy to.. :)

How can deduced the four principles of thermodynamics from Quantum Physics and that the law that thermodynamics of a system is always greather than Boltzmann Constant K

I've started few days ago to study quantum physics, and there's a thing which isn't clear to me. I know that a quantum state is represented by a ray in a Hilbert space (so that ##k \left| X \right\rangle## is the same state of ##\left| X \right\rangle##). Suppose now to have these three states...

I've read a lot of the basic things about them and I'm really interested in them but I honestly have no idea where to start looking at! I'm guessing can't start on quantum mechanics so could someone tell me everything I'd need to learn before taking them on? I'm 14 at 9th grade and so far I know...

Is it possible to make money publishing a Physics Research Paper? Why should one disclose advance quantum research and development to the physics community without compensation? I have been working, part time, for 12 years and would like to be compensated for new discoveries in quantum physics...

Could someone please explain to me the concept and theories of 'Quantum Physics', as I am quite perplexed at this topic, but simultaneously intrigued at the thought of it.

Ref: R.K Pathria Statistical mechanics (third edition sec 5.2A) First it is argued that the density matrix for microcanonical will be diagonal with all diagonal elements equal in the energy representation. Then it is said that this general form should remain the same in all representations. i.e...

Hi, can anyone recommend some good beginner quantum physics books? I don't have much knowledge of the subject and am looking for a good starting point.

I understand that the electron degeneracy principle states that no two electrons can occupy the same space at once. However, I do not think I clearly understand the physics behind that. I talked to my physics teacher about this and he said it had to do with the electron spin; I thought it was...

Homework Statement Hi everyone. This is my first time on her so I hope I make what I'm looking for clear! The question in the book says, If V(x) = ∞, x<0 ; -Vo, 0 < x < a ; 0, x > a Solve the schrodinger equation for E < 0 inside and outside the well. Apply the boundary conditions at x...

Sorry I am new to quantum physics. I am curious about what is the most accurate theory till now to predict quantum behavior. And I have several questions. 1. Is quantum field theory a "method" and can used universally in standard model? 2.What is the most accurate theory(or model) recently in...

Homework Statement Prove (6-44) which expresses the reflection and transmission coefficients in terms of the ratio E/V0.Homework Equations [/B] The Attempt at a Solution express k1 and k2 in terms of V/E? [/B]

Homework Statement since the bombarding electron has only 7.0eV ... it's not sufficient for the electron in the ground state to be excited which needs 10.4eV , so no excitation occur. and in my opinion, the bombarding electron should emerge with the same amount of energy ... but the ans given...