# All Questions

56 views

### the action of $\bar \psi \psi$ on a one-particle state

Suppose, in the quantized theory of Dirac field, we start with some one-particle state $|\vec p\rangle\equiv a^\dagger_{\vec p}|0\rangle$ in the Fock space. What is the action of the operator ...
22 views

### Why is radiation at the relativistic limit characterized by 1/gamma angle?

Trying to think of a reason as to why? Also, the factor that radiation is zero on axis? I haven't been able to resolve these two fundamental principles in my head :(
78 views

### Questions about the second law of thermodynamics

I can not understand the second law of thermodynamics and have trouble explaining the following questions: 1) In the tropics the water near the ocean surface is warmer than the deep water. Does the ...
53 views

### Realistic interpretations of quantum entanglement: Are there alternatives to the “Transactional Interpretation”?

Quantum entanglement bridges space and time: entangled particles show correlations independently of where and when they are measured. This is most evident in "delayed choice quantum eraser" ...
56 views

### Fresnel's explanation of rectilinear propagation

How did Fresnel explained the phenomenon of rectilinear propagation of light using concept of half period zones?
57 views

### Measurement of speed of static electric field propagation?

Could one measure the time delay between charging up an electrode and measuring the static electric field at some distance? For example I've looked up the specifications of an Electric Field Meter ...
20 views

### about vosges landscape and natural water transportation

Hi, there is no geologic/geographic communities on stackexchange.com, so I ask here. The Vosges are « horst », I'm not sure, but I guess they are also what people called « Anticline ». I read that ...
57 views

### Convective heat transfer coefficient for counter-current flow

This is not a counter-current heat exchanger. It is two phases, Gas and Water, flow in one flow path but in opposite direction. I have found many source doing analysis on flow pattern of the ...
69 views

### Phase shifting using the Hilbert transform

I am still struggling to understand how the phase shift of a complex signal works. Today I stumbled over the Hilbert transform and heared that it is possible to phase modulate a signal $f(t)$ ...
10 views

### What's Polarization in case of Blazars' emission?

It's known that the emission from Blazars is highly polarized. WHat does that mean? Is it simply another way of stating that blazars have highly collimated and beamed emission?
19 views

### How to derive the exponential distribution for the Pool-Frenkel effect?

For the Pool-Frenkel effect, the external electrical field $E_{ext}$ reduces barrier by a potential energy amount $U_{ext}(r_{m})$, where $r_{m}$ is the distance maximizing the total potential enrgy ...
49 views

### Difference between RPA and generalized RPA

The random phase approximation (RPA) is an approximation method in condensed matter physics and in nuclear physics. What is the difference between RPA and generalized RPA?
29 views

### Boundary effect on the Beer-Lambert for F-center/photon interaction

The Beer-Lambert law is: $I=I_{0}e^{-n\sigma(\lambda) x}$, where $n$ is the volume concentration and $\sigma$ the "efficient" cross-section. For interaction with F-centers (kind of crystal ...
36 views

23 views

### Detailed balance formulation in solar cells?

Hello I wanted to know where does the integral of following picture come from and what are the alternatives in it? How and where can i find information i need to know to understand this text? thank ...
29 views

### Quantum wave interference in 3d space

Why, in the double slit experiment, is there an interference pattern only along the horizontal axis and not along both axes?
59 views

### What if the surface charge on a conductor is positive?

This site says that if the field at the surface at the conductor has a parallel component, then the surface charge will move, which is impossible if the conductor is at equilibrium. But I learnt ...
36 views

### Force exerted by a capacitor on a polar object

I was reading about capacitors and wondered what the force an electrostatic field created by a capacitor would be on an object with a certain charge and mass. If it can exert a force on a polar object ...
37 views

### Standard Heat of Combustion

When considering tabulated standard values of heat of combustion (∆H° combustion) or any other similar value, the results are reported for species in their standard states (1 bar pressure, 25°C, etc). ...
75 views

### How to achieve Gigavolts?

I was searching the internet when I found this article http://arxiv.org/abs/0804.1764, about achieving high voltage and power to ignite thermonuclear reaction by inertial confinement, the plan was to ...
35 views

### Shrinking and Expanding objects in a CFT

In a conformal field theory, is it possible to construct a machine that shrinks or expands objects?
36 views

### Difficult to visualize Franck-Condon overlap

The franc condon principle says about the vertical transitions, means the coordinates of the nuclei remains unchanged during an electronic transition. But, what is the physical meaning or how to ...
15 views

### Zinc is more electronegative than copper,than also why it happens?

Despite the fact that zinc is more electronegative than copper,why it will lose electrons more readily than copper in the voltaic cell due to sulphate ions.
45 views

### Working of dry cell battery!

please help me out in this query!! actually i need to know why when we use a battery or dry cell, As we know it consists of :- 1)electrolyte 2)cathode and anode. but i need to know as electrolyte ...
56 views

### Meaning of Eigenvalues/Eigenvectors of a linear system of equations

I have a 41x41 system of linear equations (inhomogen) which I derived with Eureqa by describing the timecourse of fMRI haemodynamic data from a brain area as a function of the timecourses of 40 other ...
18 views

### Can unexposed PMMA be reused (successfully exposed) after development?

Can unexposed PMMA be reused (successfully exposed) after development? To clarify, PMMA is exposed using an electron beam in an SEM, and then the exposed areas are removed using a developer solution, ...
46 views

### How to interpret Lenz's law in STR?

By the Lenz's law, when a charged particle goes through a coil it generates a magnetic field. This field generates a current in the coil, slowing down the particle. But by Special Relativity (STR), ...
57 views

### Notation for Propability Amplitudes

I've recently stumbled upon a certain piece of notation that doesn't quite seem clear to me. When discussing the amplituhedron, my teacher mentioned the relation between the volume and the amplitude ...
21 views

### Radiometric Intensity of Non-Monochromatic LED

So I have a problem with the LED with the spectrum shown below I am asked to find the radiometric intensity in Watts/steradian given that the LED produces $5.6\times 10^{-3}$ mcd. We are also told ...
75 views

### range of the difference of two-qubit density matrix determinants

The determinant of a two-qubit (4 x 4) density matrix lies between 0 and (1/2)^8. (A pure state has determinant zero, and the fully mixed [classical] state, determinant (1/2)^8.) The determinant of ...
39 views

### How to analyse data that is in four dimension?

I have obtained a series of data that is about density distribution of liquid in three dimensions, density$=f(x,y,z)$. How can I know the detail information about the way that density changes with $x$ ...
Given the Hamiltonian $$H=p^{2}-ge^{-x},$$ are the energies negative? If I impose the boundary condition $y(0)=0$ and $y(\infty)=0$, I get the condition for the energies  J_{2i \sqrt{E(n)}}(g) ...