Quantum physics Definition and 717 Threads

Besides the basics what are the theories in math that I need to know for learning quantum physics? And what books do you recommend for learning then?

Hi ! In my class we have an exercise that I technically understand but that I can't get conceptually. We have trois molecules (naphtalene, anthracene, tétracene). Considering each molecule as infinite quantum well of length 2L(naphtalene), 3L(anthracene) and 4L(tetracene), we would like to...

Dear All, I have a question on the double slit experiment. From the references I've read so far, they are focusing on the results of the detector AFTER the 2 slits. Let's say when photons are fired, how many % actually pass through the slits and get detected at the end? Would some (and how...

If you shrunk an atom down to a certain point would it become a black hole like all matter in the universe can? How big would it be?

Dear Everyone, We are a research group doing research in computational sciences. We are considering ordering new computers for our research. I was wondering if anyone could advise us regarding the hardware specifications needed to run heavy and time-expensive programs, specifically in...

I am looking for a derivation of the following formula $$ \eta=\lim_{\omega\rightarrow0} \frac{1}{2\omega}\int dt dx\langle[T_{xy}(t,x),T_{xy}(0,0)]\rangle, $$ where $T_{xy}$ is a component of the stress-energy tensor. This is claimed in for instance https://arxiv.org/pdf/hep-th/0405231.pdf...

Hey! I posted this thread hoping that there are experts about quantum physics here. Please if you do not know a lot about the subject, don't answer this question: First things first, to be clear: I’m NOT building a quantum suicide machine and I’m NOT trying to kill myself. I’m just curious...

In the book of Modern Quantum physics by Sakurai I wonder how 1.6.26 can be 1.6.27.

A particle is in its ground state of an infinite square well of width a <xl i>=√2/a*sin(πx/a) and since it's an eigenstate of the Hamiltonian it will evolve as <xlα(t)>=√2/a*sin(πx/a)e^(-iE1t/ħ) where E=π2ħ2/2ma2 If the well now suddenly expands to witdh 2a If the well suddenly expands to 2a...

Hello, here there are 2 things (one about hologramic universe and the other about a quantum physics test similar to the slit lamp. The first one is about the Bohm and Pibram as well as one about Alain Aspect 1982 study: articles about their theories...

If you were to explain what quantum physics is by first introducing the historic experiments/observations undertaken by scientists and then explain the different possible accepted interpretations and theory... How many experiments would you need at least? Which ones? Double Split Experiment...

Hello there. I'm here to request help with mathematics in respect to a problem of quantum physics. Consider the following function $$ f(\theta) = \sum_{l=0}^{\infty}(2l+1)a_l P_l(cos\theta) , $$ where ##f(\theta)## is a complex function ##P_l(cos\theta)## is the l-th Legendre polynomial and...

Hello there, I'm new. I'm a high school student, currently in a physics class, trying to teach himself some basic quantum mechanics. My teacher can offer limited assistance, since she doesn't want to force the rest of class to do this stuff, and considers me slightly mentally ill for attempting...

Hello, I'm studying the section 2.2 of "Introduction to Quantum Mechanics, 2nd edition" (Griffiths), and he shows this equation $$\frac{\partial^2\psi}{\partial x^2} = -k^2\psi , $$ where psi is a function only of x (this equation was derivated from the time-independent Schrödinger equation) and...

Homework Statement I'm doing problems for practice in quantum physics. Consider two particles of the mass m in one dimension with coordinates being denoted by x and they are connected by a spring with spring constant k. Suppose that the total momentum of the system is p. Find all possible...

Homework Statement Consider a particle with angular momentum l=1. Write down the matrix representation for the operators L_x,\,L_y,\,L_z,for this particle. Let the Hamiltonian of this particle be H = aL\cdot L-gL_z,\,g>0.Find its energy values and eigenstates. At time t=0,we make a measurement...

I'm really interested in quantum physics and want to my own learning on it,but what does it contain, generally? And where should I start with it?

If you consider the one-dimensional case of a particle constrained to move on the edge of a circumference, the energy spectrum is continuous and two times degenerate. Why the fact that the particle can move in clockwise and counterclockwise implies that the spectrum is degenerate twice? In any...

Does this paper [https://arxiv.org/pdf/1505.06963.pdf] give sufficient reason to accept/believe that the infinities where we "find" singularities can never really happen because there is a minimum length scale that prevents it? Hoping that I have made at least a reasonable deduction from the...

There is one thing that I don't understand when considering quantum mechanics for macroscopic bodies. It is said that classical mechanics is a valid approximation and that macroscopic bodies that we encounter on everyday basis have a small uncertainty in position and momentum. So far, so good...

Hi! I'm an undergraduate student studying mechanical engineering with some numerical knowledge of astrophysics. If I want to start learning quantum physics by myself, which books should I start reading? Thanks!

What are the main maths used in the mentioned fields of physics? Not just general terms like "Calculus" but more specific maths. Also, what is the logic behind using these to solve problems in physics? Example, why would someone use differential calculus to calculate the probability of a...

Hello Everyone, While deriving potential energy stored in space due to two stationary opposite charges we end up with negative value of energy which upon dividing by c square provides us with negative value of mass. What is the significance of this mass other than reducing the total mass of...

For some time I've been wondering how to eloquently distinguish classical and quantum physics. What I mean by eloquent is both simple and short. By simple I mean understandable to any college freshman, and with that caveat, as short as possible. Something like: "quantum has inherent randomness...

I am trying to figure out what winfield oh physics i should study for a career. I absolutely love learning about strange quantum phenomena but also love learning about extremely small particles and how they interact at the smallest of scales Would i be interested in a career in particle physics...

I want to be a quantum physicist as a career because i absolutely love the mystery behind certain principles in quantum physics. Especially things like the quantum eraser experiment. I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic...

This is my final year at high school and i don't know which college is better for study. i love physics and chemistry especially nuclear subjects So i have lots of questions like what I'll study and the applications of it , where I'll work and which one is deeply focus on nuclear stuff...

hi my name is Shane and I am currently in college but my college does not help in that branch of science, I am in England Suffolk and I am 17, I was wondering if anyone had an idea where I could start

Homework Statement See Image The bit about Spectral lines, I couldn't explain why[/B] Homework Equations ΔEΔt≈h The Attempt at a Solution I expected the histogram to peak at the given mass in question and to have a width of about 0.08 MeV calculated as ΔE from the Energy-time uncertainty...

This delayed choice quantum eraser experiment captured my attention and after deep thought about it, I find it really startling and totally punishing to my common sense. My question is: Can you predict the future, say, a human's mind, using the quantum eraser? I imagine a modified version of the...

What would the world be like if the speed of light is infinity and the Planck constant is zero (therefore the world is totally Newtonian)?

I am a physics student from Spain and hopefully I will be finishing my degree in physics (4y) by next June. I am trying to decide on a Master's program to study but I am finding very difficult to decide since there are so many oportunities and so diverse specially when looking for programs...

I was doing some reading on String Theory...I'm not a scientist, but i enjoy it (so forgive me if my question is stupid) and i was wondering: Being time a dimension, could it be the dimension the strings exist in? And interaction between all particles and all forces determine how they vibrate...

Basically, I found the energy of a photon using its frequency ((6.8*10^15) and E=(3.6496394*10^-16)) and so I then used "p=E/c" to find the momentum and got 1.2173887*10^-24 however I don't know the measurement of the momentum. Is there a better equation to use to find momentum, and what would...

Homework Statement Let ##\left|\psi\right\rangle## be a non-degenerate stationary state, i.e. an eigenstate of the Hamiltonian. Suppose the system exhibits symmetry for time inversion, but not necessarily for rotations. Show that the expectation value for the angular momentum operator is zero...

I always hear that the two 'don't match' and disagree, but never in what... Someone mind explaining?

What is the difference between the concept of scale in the SM QFTs and the scale concept in geometry? In other words, QFT is a scale-dependent theory that is living on a scale-invariant space(either R4 or M4, related by Wick rotations). Mathematically scale-invariance and scale-dependence appear...

I am trained in aeronatical engineering, spent a number of year supporting sounding rockets in the exploration of the Upper Atmosphere. Retired 16 years ago. Am interested in General Relativity and Quantum physics. Looking to explore and understanding of entropy... Black holes... Etc.

Thanks in advance to all who reply. Forgive me if this naive, I am not scientifically inclined, but I am VERY curious. After re-watching a documentary on quantum physics, I have a "thought experiment" that I would like feedback on. Maybe this experiment (or something like it) has already been...

I'm reading Gasiorowicz's Quantum Physics and at the beggining of chapter 2, SG introduces the concept of "wave packet" and gaussian functions associated to them. The first attached image is the 28th page of the book's 1st edition I suppose, and my question is about the paragraph inside the red...

Hi! For the probability interpretation of wave functions to work, the latter have to be square integrable and therefore, they vanish at infinity. I'm reading Gasiorowicz's Quantum Physics and, as you can see in the attached image of the page, he works his way to find the momentum operator. My...

Homework Statement Normalized equation for particle in a ring, where V=0 on a ring of radius 'a' and infinite everywhere else. Homework EquationsThe Attempt at a Solution Replcing x by rθ, $$-\frac{\hbar^2}{2I}\frac{\partial^2\psi}{\partial\theta^2}=E\psi$$ By guess, I found out that...

Homework Statement The radial wavefunction for ##3d_{z^2}## orbital is $$R=N\sigma^2e^{-\frac{\sigma}{3}}(3\cos^2\theta-1)$$ $$\sigma=\frac{r}{a_0}$$ Find r and θ for which the probabiity of finding the electron is maximum Homework Equations None The Attempt at a Solution ##R^2## gives the...

TheAdmin submitted a new PF Insights post Interview with a Physicist: David J. Griffiths Continue reading the Original PF Insights Post.

In a hydrogen atom, the wave function is written as R(r).Θ(θ).Φ(φ). But how is it separable when the electron is interacting with the nucleus?

Homework Statement For the particle in a box given in the above question, what is the probability of finding the electron between (i) x = 0.49 and 0.51, (ii) x = 0 and 0.020 and (ii) x=0.24 and 0.26 ( x in nm) for both n=1 and n=2. Rationalize your answers. Homework Equations...

We've learned Q&M in modern physics but I need to make sure I'm getting this concept right... So the photoelectric effect demonstrated the fact that a photon (wave) can knock an electron out of a metal, which could only happen if a photon was a particle. So much for photons being waves. I get...

Hello, I am very interested in learning Quantum Physics however I want to know what the prerequisite knowledge is, what math and physics i require before taking up Quantum Physics. I would really appreciate it if someone could make a list or something of that sort so I could know where to...

In our BS Hons course, we stumbled upon quantum physics. This aforementioned topic is, if not, completely new to me. Therefore, for a better understanding and easy to understand book is necessary; not compromising on the mathematical side though.

Hello I'm hard at work trying to find a pattern for the prime numbers and this keeps cropping up. To be honest though, to me it comes across like pseudo science. I mean I never really hear people talk about it. This seems an obvious thing to look into but I don't know anyone who does. Prime...