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The total horizontal distance traveled by a bouncing ball nudged off a table of height $H$ [closed]

Suppose a ball gently rolls off a flat surface of height $H$ and free falls to the ground subject only to the law of gravity. Once the ball hits the ground, it rebounds as shown in the figure. When ...
user42700's user avatar
  • 101
0 votes
0 answers
21 views

How to count simple resistor circuit configurations? [closed]

Really stumped by this one (I'm not an EE!). Suppose we are given 1, 2, 3, 4, 5, and 6 one-ohm resistors. They can be arranged in series, parallel, bridge, and so forth circuits. No dangling resistors ...
Ken Bannister's user avatar
3 votes
1 answer
70 views

Non-crossing approximation (NCA) in 'Large-$N$ expansion' (Altland & Simons CMFT)

I have a question about non-crossing approximation (NCA) stated in Condensed Matter Field Theory by Altland & Simons1. It is on page 200-203 for the 3rd edition (on page 223-227 for the 2nd ...
Jinu.P's user avatar
  • 31
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0 answers
36 views

Isentropic or isenthalpic expansion for the remaining fluid in a previously pressurised tank? [closed]

Imagine a container filled with ammonia at 25 bar and 100 degC. Assume that an orifice is opened, so that fluid can flow through ...
Felix's user avatar
  • 3
2 votes
1 answer
146 views

QFT with massless particles

EDIT: Often in textbooks one discusses QFT with massless particles, e.g. massless fermions or scalar particles. What mass vanishes: bare or physical? or both?
MKO's user avatar
  • 2,226
3 votes
1 answer
503 views

How accurate does the ISS's velocity and altitude need to be to maintain orbit?

We know the the ISS is not drifting weightless in space, but rather is constantly falling as it circles the Earth. To do this it must be at a specific altitude and moving with a specific velocity. ...
foolishmuse's user avatar
  • 4,783
1 vote
0 answers
47 views

Numerical Solution of the circular restricted three body problem [closed]

I am trying to numerically solve the differential equations in the planar circular restricted three-body problem. In the rotating frame, the differential equations are given by \begin{equation} \...
Markus Hamre's user avatar
2 votes
0 answers
33 views

Difference between boundary conditions in thermodynamic limit

Consider a model for a spin chain. I somehow am able to find a general formula for the expectation value of some observable in both periodic and open boundary conditions. ie., under PBC, I have $\...
Souroy's user avatar
  • 193
0 votes
0 answers
27 views

Off-centered IMU and how to determine the centripetal force acting on it

I apologize if this is the wrong place to ask questions about IMUs and how they work. My question is: if a 6-DOF IMU is placed off-center from the center of mass of the body being measured, and the ...
Reaver_332's user avatar
0 votes
1 answer
55 views

Components of the reaction forces against a fluid along the horizontal and vertical axes for slanted walls

I came to know that the reaction force (normal force) exerted by the walls of a vessel against a fluid is normal to the surface area of the vessel, which is the nature of a normal force. Also, at any ...
soumyadip_poddar's user avatar
1 vote
1 answer
134 views

Some confusion about understanding the relativistic quantum mechanics

S. Weinberg in his book "The quantum theory of fields" chapter 2 introduced the notion of symmetry in quantum mechanic as follows: Physical states are represented by rays in Hilbert space. ...
Mahtab's user avatar
  • 374
1 vote
6 answers
117 views

Heating an object with black body radiation to above the temperature of the source

A recent question and its answers say that you could not use sunlight to heat something to above the temperature of the Sun. There was some discussion of the need for the bodies to be in ...
badjohn's user avatar
  • 2,075
1 vote
0 answers
48 views

What is the physical meaning of the average value of the long product of spin operators

For the quantum one-dimensional XYZ Heisenberg model with $N$ spins $1/2$, consider the following average values of the products of successive operators $\hat{\sigma}^x$ in the ground state $$ C_j(n) =...
Gec's user avatar
  • 5,697
0 votes
3 answers
48 views

What happens to the charges in an inductor when you induce a voltage?

Say you have two inductors, and - very much like a transformer - you connect the first one to a voltage source, then place the other one close to it, so that there will be an emf induced by the change ...
cabutchei's user avatar
0 votes
0 answers
97 views

Dirac's Bracket Notation

I have a question on Dirac's bracket notation. In particular, according to this notation, vectors and covectors are represented by $|\psi\rangle$ and $\langle\psi|$ respectively. Moreover, these two ...
Falcy87's user avatar
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0 votes
3 answers
83 views

When is the temperature relevant for a quantum many body system?

Let me illustrate my question with an example. Suppose I want to consider a system of $N$ identical bosons. The Hamiltonian of the system is typically of the form: $$H_{N} = \sum_{j=1}^{N}(-\Delta_{x_{...
MathMath's user avatar
  • 1,131
1 vote
0 answers
27 views

Verifying a Conformal Ward Identity for the Free Boson

I've always been very uncomfortable with the following two conformal Ward identities [c.f. Di Francesco, pg 107, Eqs. (4.66) and (4.67)]: $$ \langle (T^{\rho \nu} - T^{\nu \rho})X \rangle = -i \sum_i \...
Zack's user avatar
  • 3,098
0 votes
2 answers
82 views

What would happen to the moon's orbit if we reduce (instantaneously) its mass? [closed]

In my opinion the moon's orbit shouldn't change, because an orbiting body is a free falling object and the trajectory of a free falling object is not affected by its mass (because the inertial mass ...
Suppiluliuma's user avatar
0 votes
0 answers
36 views

Calculating Bandgap of material from specular reflectance vs diffuse reflectance

I am looking for some clarification on whether specular reflection data can be used to calculate the bandgap of a material. I am using a UV-vis spectrometer and measuring the reflectance from an ...
user668074's user avatar
1 vote
0 answers
36 views

Derivation of the Equivalent Photon Approximation in Peskin and Schroeder

I am trying to reproduce the equivalent photon approximation as discussed in chapter 17.5 in Peskin and Schroeder but cannot justify equation (17.93). The process we are considering is the scattering ...
Lurianus's user avatar
  • 337
4 votes
1 answer
91 views
+50

Albedo of water vs temperature

This question arose out of pure curiosity. Is there a relation between the temperature of water and its albedo? Would the albedo increase if I increased temperature? Say I measure albedo by directing ...
Vivaan Daga's user avatar
-3 votes
0 answers
44 views

What is the cause of gravity according to general relativity? [duplicate]

The question is based on general relativity and it can help big bang theory.
surya dev's user avatar
-5 votes
0 answers
50 views

Can self-indication assumption solve the fermi paradox? [closed]

Consider $P$ the probability that our civilization appears from beginning to the end. $P$ should also be the probability that at least 1 extraterestrial civilization exists. If we asses that $P$ is 50%...
Thheo_sc2's user avatar
1 vote
1 answer
53 views

Time evolution of operators in the path integral formalism

I have studied the Hamiltonian formulation of non-relativistic quantum mechanics (NRQM) in detail but have limited knowledge of the path integral formulation. In the interaction picture of the ...
SCh's user avatar
  • 756
0 votes
0 answers
79 views

How might you quantise this non-polynomial action?

I am interested in the following non-polynomial action: $$L = \sqrt{(\partial_\mu \phi \partial^\mu \phi^2 + m^2 \phi^2 -\lambda^2\phi^4)^2 + \varepsilon^2 } dx^2 $$ where $\varepsilon$ is very small....
bob's user avatar
  • 117
0 votes
3 answers
78 views

Is the kinetic energy of a rotating system just the sum of the instantaneous kinetic energies of the individual particles?

Take a look at this construction which shows linearly moving particles giving the illusion of circular motion. (Follow the instructions on the screen). Now the question is when I calculate the total ...
KDP's user avatar
  • 6,102
-2 votes
0 answers
53 views

Force applied by hand, force applied by the spring and the corresponding work done

Consider a block of mass $m$ is attached to a massless spring of force constant $k$. If the spring is pulled by hand so that it stretches by an amount $x$, its potential energy increases from zero to $...
Solidification's user avatar
-1 votes
0 answers
37 views

Is my vector notation in electrostatics correct? [closed]

Let’s say we are expressing Coulomb’s law in Cartesian coordinates (not radial). Let the two charges of equal magnitude (and opposite sign) lie on x-axis. The equation for calculating the force acting ...
Alexander Djurovich's user avatar
0 votes
0 answers
50 views

Given Green's function, can I find the corresponding operator? [migrated]

Green's function is the solution to the equation $L G(x;x') = \delta(x-x')$, where $L$ is a linear differential operator. Usually, we want to find the Green's function of a given $L$. Instead, if we ...
Sean's user avatar
  • 101
-1 votes
0 answers
16 views

Parallel plate capacitors with dielectrics [closed]

I was studying capacitors with dielectrics ,where my teacher gave one example for us to solve between the parallel plate capacitor there is dielectric which is further divided into four dielectrics ,...
Kushagra Mishra's user avatar
-5 votes
0 answers
82 views

Where can I publish a paper on an overhaul of quantum mechanics and relativity, for peer review? [closed]

I am working on a theory that combines quantum machanics and special relativity, the paper is by no means ready, I am just wondering where I could publish it for peer review when it is. I have never ...
Xeno's user avatar
  • 1
8 votes
5 answers
2k views

Does color temperature limit how much a laser of a given wavelength can heat a target?

The Sun has a peak wavelength of around 500 nm and an effective surface temperature of 5770 K, and sunlight cannot be focused to make something hotter than the Sun, because this would be heat flowing ...
causative's user avatar
  • 912
0 votes
2 answers
93 views

Why don't disturbances/wind move at the speed of sound in air?

Why don't sound waves move at the same speed as air that has a pressure differential? Imagine you have a box that is filled with air. One half high pressure air, the other half low pressure. They are ...
Wyatt's user avatar
  • 275
-2 votes
0 answers
52 views

Which field of computing looks more promising, the biological computers that have been springing up or quantum computers? [closed]

Hello this is my first question on this site so thank you for taking a look. Anyways as an aspiring electrical engineer I try my best to keep up with the current trends. Such that I’ve noticed two ...
Arthuro Cisneros's user avatar
1 vote
0 answers
76 views

Why are quantum-many body problems difficult to solve? [duplicate]

I am a little confused about which classes of interacting many-problems are considered intractable. Suppose I have some tight-binding system with some nearest-neighbor density-density interactions, ...
meer23's user avatar
  • 51
0 votes
0 answers
37 views

Measurement of position using a lens [closed]

I am slowly reading the first chapters of Schiffs Quantum Mechanics and I don't understand where does this uncertainty of the measurement of x comes from and how exactly does this experiment work. I ...
Zuzia Woźniak's user avatar
1 vote
0 answers
42 views

Draw the angle graphically [closed]

Hi everyone (sorry for the "unclear" title), I'm having trouble graphically representing the point of this: A stone is thrown from the top of a tower with $h = 50\text{m}$ and with a ...
Pizza's user avatar
  • 11
0 votes
0 answers
76 views

What is the difference between material time derivative and total time derivative of a tensor field? [closed]

I consider material coordintes as $(X_1(t),X_2(t),X_3(t),t_0),$ ($t_0$ arbitrary) and space coordinates as $(x_1(t),x_2(t),x_3(t),t).$ $\textbf{Remark.}$ I am interested just in dim=3. We consider a ...
pikunsia's user avatar
1 vote
1 answer
71 views

Can black holes fully merge, according to a distant observer? [duplicate]

According to a distant observer, an object falling into a black hole doesn't disappear behind the even horizon but rather red-shift due to time dilation. Does the same apply to merging black holes? ...
Michael's user avatar
  • 1,951
-2 votes
0 answers
26 views

Simulate Temporal Coherence [closed]

Which Optical simulation software can simulate Temporal Coherence? I need to simulate temporal coherence, how I can do this?
mohammad ali hossain's user avatar
-1 votes
0 answers
28 views

How to determine the speed and acceleration of an item moving vertically when another item moves horizontally? [closed]

A horse lifts a bucket with a rope and a pulley. Find the velocity $v_{a}(x)$ and acceleration $a_{A}(x)$ in terms of $x$. How do I go about solving this? What is wrong in my attempt?
Delta Foxtrot's user avatar
0 votes
0 answers
58 views

Eigensystem of part of the representation of the position operator: $a^\dagger+a$ in the base of the quantum harmonic oscillator [closed]

What are the exact eigenvalues and eigenvectors of the following matrix? \begin{equation} \begin{pmatrix} 0&\sqrt{n}&0&\cdots&0&0\\ \sqrt{n}&0&\sqrt{n+1}&\cdots&0&...
Thanos Athanasopoulos's user avatar
7 votes
1 answer
651 views

Photon propagator in path integral vs. operator formalism

I am self-studying the book "Quantum field theory and the standard model" by Schwartz, and I am really confused about the derivation of the Photon propagator on page 128-129. He starts ...
Andrea's user avatar
  • 613
0 votes
0 answers
10 views

Modeling centrifugal distortion with an effective charge distribution

The hamiltonian of a rigid object with a totally symmetric moment of inertia (i.e. a "spherical top") will depend only on the magnitude of its angular momentum. If we allow the object to ...
creillyucla's user avatar
0 votes
2 answers
59 views

Some questions regarding a pulley [closed]

Please have a look at the following diagram sketched by my Professor. The points $P_1$ and $P_2$ have mass $m_1$ and $m_2$ respectively . The pulley is frictionless and it is represented by a ...
Davide Masi's user avatar
-4 votes
1 answer
64 views

As I read an article on this website that light cannot warp space time fabric [closed]

But actually we know that energy is equals to mass then light energy can act like mass and it can create a black hole made up of light . As per Einstein equation E=mc² then why there is no black hole ...
Arpit Jha's user avatar
0 votes
6 answers
152 views

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

In my book, Concise Physics of Selina Publications for Class IX, it's written there that "If there is no transfer of heat between the two bodies placed in contact, they are said to be at the same ...
Kakiaririki's user avatar
0 votes
1 answer
36 views

How does Shear Force on a fluid in a vessel reaches an equilibrium if molecules are free to make contact?

In Hydrostatic, if the fluid is a perfect fluid that is non-viscous, it doesn't experience any shear force because if it would experience so it might start flowing so something might be working to ...
soumyadip_poddar's user avatar
0 votes
2 answers
48 views

Why the frequency component is not included when the energy of a wave is described?

Energy of a wave is directly proportional to its Amplitude squared. There is no inclusion of frequency in it. But by intuition if one thinks about it, isn't it obvious that a wave with higher ...
Vibhav shivadeker's user avatar
3 votes
1 answer
361 views

From what equations is magnetic field uniquely determined for a given current distribution?

The Maxwell equations for magnetostatics in the absence of time varying electric field state that - $$ \mathbf{\overrightarrow{\nabla}} \cdot \mathbf{\overrightarrow{B}} = 0 $$ $$ \mathbf{\...
Bipul Kumar's user avatar

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