# All Questions

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### Introduce Ghost Field to eliminate unphysical degrees of freedom in case of Photon Field

In wikipedia's article about ghost fields is mentioned that An example of the need of ghost fields is the photon, which is usually described by a four component vector potential $A_{\mu}$, even if ...
1 vote
44 views

1 vote
24 views

### Landau Ginzburg path integral (PI) for the Ising model at gaussian order

I am stick with a problem in computing explicitely the gaussian PI in the Landau-Ginzburg theory for the Ising model. If we do a procedure of coarse graining, we can define $m(x)$ as a continuous ...
95 views

### Mathematical objects on crystal meltings and their relation to particle physics

I am a mathematician interested in analytic number theory, and I found the paper Dimers and Amoebae , which shows how many mathematical objects like the Mahler measure, the Ronkin function and the ...
331 views

### Wave amplitude as a complex number?

In section 1-3 An experiment with waves of The Feynman Lectures on Physics (https://www.feynmanlectures.caltech.edu/III_01.html) it says: "The instantaneous height of the water wave at the ...
44 views

### Why is the $ΔT$ for the heat transfer of the copper segment, like in the picture, $(100 - T)$ instead of $(T - 100)$? [closed]

Image taken from the linked video So, I was trying to figure out the answer for a problem very similar to the one in this video, where I have to find the temperature T at the middle of the ...
43 views

### Trajectory Equation for Pitched Baseball [closed]

I am working with a [NASA Curveball simulator] (https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/ballkiosk/) and am trying to come up with equations to match its results. Unfortunately, [NASAs ...
1 vote
33 views

### Coupling two Ising chains via an energy-energy interaction

Consider the transverse-field Ising model on a chain with periodic boundary conditions: $$H = -\sum_{i=1}^{L} \sigma_{i}^z \sigma_{i+1}^z + h \sigma_{i}^x$$ There's a phase transition at $h=1$, which ...
65 views

### Doesn't matter collapsing inside a black hole spin at the speed of light?

Once an event horizon is formed in the process of the gravitational collapse of a star, the original star collapses inside the event horizon. As far as we know, stars and in particular neutron stars, ...
56 views

### Are creation and annihilation operators functions of momentum?

In QFT, we usually write creation and annihilation operators in the following way: ${a^s_{\textbf{p}}}^\dagger$, $a^r_{\textbf{q}}$, where $r,s$ denote the spins and $p,q$ the three-momenta of ...
14 views

### Change of scaling due to a perturbation

I am looking for known examples of models where the introduction of a perturbation changes the scaling law of one or more observables. I would appreciate suggestions relevant to any branch of Physics, ...
22 views

### Is the normal to an embedded surface generally undefined up to a connection?

Let there be an embedding $\phi:S\rightarrow M$ where $M$ is a d-dimensional manifold and $S$ is a codimension-k submanifold. the space of all tangent vectors to the embedded surface $\phi(S)$ is ...
60 views

### How to find the optical path difference between two non-parallel light rays?

Consider this Thin Film Interference diagram here. The Optical Path Difference (${OPD}$) between the reflected light rays from ${C}$ and ${A}$ is $$OPD = n_{2}({AB} + {BC}) - n_{1}{AD}.$$ I can ...
31 views

### AC Node analysis [closed]

i want to ask about the concept of ac anlysis in the following question,i want to find the value of Vc here is the soluion Here is the equation to find out the value of Vc I know i1+i2+i3=0 in the ...
51 views

### What causes this fluorescence-like effect?

I have a New Year's garland that emits blue light: When I turn it on and turn off all other lights in the room, almost all objects in the room would be colored in different shades of blue - as I ...
31 views

### Light doppler effect to low velocity [closed]

Show that for low speeds the Doppler effect of light can be written in the following approximate form: $$\frac{\Delta \lambda}{\lambda} = \frac{v}{c}.$$ I don't have many ideas. Can anyone help me?
29 views

### Frequency Dependent Absorption According to Wu

I was reading the paper "Theory of strong-field attosecond transient absorption" by Wu, and he says that the difference in energy of a material interacting with an electromagnetic field (...
16 views

### What is the point of the booster/sonotrode combo in an ultrasonic cutter? Can it be replaced with a single flat sheet of metal? [closed]

I want to make an ultrasonic cutter for home use projects, something like this or there are many online videos of industrial ultrasonic cutters in e.g. the food industry. A typical design of an ...
22 views

### How does photoelectron yield quantum efficiency change for metals in presence of electric field?

Figure 1 of this paper gives quantum efficiency for stainless steel. https://arxiv.org/pdf/1503.08074.pdf However, I am interested in photoelectron yield quantum efficiency for stainless steel at 4kV/...
30 views

### Difference between friction force and force because of friction?

I'm doing some physics studying right now and the wording of an example question really confused me so I was hoping to get help in figuring it out. It says that " The coefficient of friction ...
54 views

### Explicit Form of Feynman Propagator for a Scalar Field in Position-space: Derivation Details

This is Problem (6.1) from Schwartz's QFT and the Standard Model. I am trying to directly calculate, by performing the integral over momenta, the explicit position-space expression of the Feynman ...
61 views

### About Second-Order Poles of Matsubara Sum

I would like to ask about the calculation regarding Matsubara sum of the form \begin{equation} \frac{1}{\beta}\sum_{i\omega_n} \frac{1}{(i\omega_n-\xi)^2} \end{equation} which is a second order pole ...
100 views

### Book on numerical solution of PDEs

I would like to learn how to solve partial differential equations (first and second order, e.g. Poisson, etc...) numerically with finite differences. Which book can be recommended if one want it to ...
18 views

### What happens to the material within a pin when it is sheared? [closed]

how do I explain what is going on within a cylindrical pin when it fails due to shear stress? specifically what happens within the material to produce the grooves and the messed up area shown in the ...
33 views

### Capillary Rise and Orientation of the beaker

When a capillary is dipped vertically inside a liquid, the liquid rises upto a height $h$. In the same capillary, the same liquid is filled in horizontal position, then it is kept in a vertical ...
56 views

### Post-Newtonian Stress-Energy tensor

I am currently studying Michele Maggiore's book - 'Gravitational Waves: Volume 1: Theory and Experiments'. On pages 245 and 246, each order --- until the second order --- of the stress-energy tensor. ...
44 views

### Unable to re-derive Inverse Transfer Matrix

I don't get the same result as the book when computing the inverse of this matrix. For context, I'm rederiving some equations from a book on acoustic waves in periodic structures, specifically a ...
46 views

### Confusion in calculation of power [duplicate]

Question- Sand is being dropped from a stationary dropper at a rate of 0.5 kg s$^{-1}$ on a conveyor belt moving with a velocity of 5 ms¹. The power needed to keep belt moving with the same velocity ...
57 views

### Newtonian 2-Body problem

The Newtonian equations of motion for two-point masses $m$ and $m^{\prime}$ are derived from the following Lagrangian: L = \frac{1}{2}m\mathbf{v}^{2} + \frac{1}{2}m^{\prime}\mathbf{v}^{\prime \, 2} +...