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I'm trying to make sense of what actually happens to light when it interacts with an opaque surface.
The fresnel equations give us the proportion of light which is reflected off the surface of a material, and the proportion of the light which is transmitted into the material. For something like glass, this makes sense... |
According to Einstein, mass bends the fabric of space-time. And nothing in the universe has infinite mass to infinitely bend space-time. So how do remnants of supermassive stars, i.e black holes infinitely bend space-time, so much so that even light can't escape it? How do black holes infinitely bend space-time when th... |
The nonrelativistic expression for the electric field of a charged particle from classical electrodynamics,
\begin{equation}
E(r) = \frac{q}{4 \pi \epsilon_0 r^2},
\end{equation}
implies the particle is infinitely narrowly localized at a point, so it does not admit an uncertainty in the position of the particle.
In qua... |
Suppose I wish to add angular momenta with some relative coefficients
$$\vec{J} = \alpha \vec{J}_1 + \beta \vec{J}_2$$
Can any one explain how this would be done? And how different would it be from the usual case of $\alpha = \beta = 1$?
|
A free particle of spin 1 is at rest in a magnetic field B, so that
$$ H_0 = −κ B_z S_z $$
where $S_z$ is the projection of the spin operator in the z direction. A harmonic perturbation
with frequency $ ω = κ B_z $ is applied in the x direction for a short time (one period of
oscillation only), so that the weak perturb... |
I have an application for a rotating disc with inertia that is put on a "knife edge" balancing fixture. The disc is then released in order to find the "heavy spot", once identified the point is rotated for 90 degrees and is released again. I record the angles with respect to time. What I've found is that I'm dealing wi... |
I am referring to
https://en.wikipedia.org/wiki/Bell%27s_spaceship_paradox
and explanations based on diagrams like
The reasoning for a resolution of Bell's spaceship paradox is mainly that the definition of equal time slices for the two observers and therefore their distance calculations yield different results, i.e
$... |
I'm following Shankar's treatment of 1D scattering in Principles of Quantum Mechanics (Page 167 to Page 172).
In general, the eigenstates of the single-step potential $$V(x)=\begin{cases}
0 & \text{for } x < 0 \\
V_0 & \text{for } x > 0
\end{cases}$$
is:
$$\psi(x)=\begin{cases}
A_1 e^{-i k_1 x} + B_1 e^{i k_1 x} & \t... |
I'm just wondering why the current density $J$ is always defined as the amount of electric current traveling per unit cross-section area $J = \frac{I}{S}$, and not per volume unit $J = \frac{I}{V}$ so $\frac{A}{m^2}$ instead of $\frac{A}{m^3}$. Wouldn't it be useful to calculate electric current density per volume?
|
Basically I am asking if gravitional lensing is bending or refracting light.
|
When we solve the single coordinate Schrödinger equation,
\begin{equation}
i \hbar \partial_t \psi = - \frac{\hbar^2}{2 \ m} \ \nabla^2 \psi \ + \ V(x) \ \psi, \tag{1}
\end{equation}
we imply the potential $V(x)$ is exactly defined everywhere on $x$ with no uncertainties, i.e. a classical $V(x)$, despite the fact tha... |
Have you ever stood above a river or lake and noticed that the surface has visible "patches"? It looks like the surface has different average wavelengths in some areas, leading to the light being reflected differently (more vs less shiny).
Something has puzzled me for a long time. These patches are quite stable. Their... |
I have an exercise with a pendulum starting at horizontal position, then we give it a velocity of 5m/s pointing down, $z=0$ at this horizontal position and potential energy = 0. This confuses me because then if we dont't have that initial velocity the mecanichal energy at start would be 0, but still the pendulum have m... |
CASE 1:
If dielectric is inserted QUICKLY then what difference will we see in the charge , potential, capacitance?
CASE 2:
If dielectric is inserted SLOWLY then what difference will we see in the charge , potential, capacitance?
(Battery is Connected)
|
I have been watching this Veritasium YouTube about Gyroscope Precession and I understand why the spinning wheel will rotate about the string. But now that the whole spinning wheel and axle is rotating about the string there must be an angular momentum component vector pointing upwards to the ceiling. But how is that ve... |
My textbook says that light ways produced by light bulbs are not coherent but it doesn't describe the reason.
I was wondering how could two waves not be coherent regardless of the source they are produced from. As far as I know coherent waves are waves having a constant phase difference, meaning their phase difference ... |
Consider any potential field $$V = V(x)$$ (not limited to gravitational potential field, but we only consider time-independent ones) in 3-d space that satisfies the following conditions:
The potential field is everywhere negative, i.e. $V(x) < 0, \forall x \in \mathbb{R}^3.$
The potential field tends to zero at infini... |
Electromagnetic induction means magnet convert it momentum to an electrical current. So I wonder if it possible to use this phenomeno for making an enigne which will accelerate a magnet And the magnet will push the spacecraft but some sort of coil will slow doen the magnet on when it getting back so it won't push th... |
In the Dirac the spinor components are defined by fermion/antifermion (here labeled as $+,−$) and spin component $S_z$ ($↑,↓$):
\begin{pmatrix} \psi_-^\uparrow \\ \psi_-^\downarrow \\ \psi_+^\uparrow \\ \psi_+^\downarrow \end{pmatrix}
We understand the first 2 components as the fermion and the last 2 components as the ... |
I was studying standing waves today and the teacher took a string attached to a fixed end then waves are produced (of equation $Asin(\omega t-kx)$ )on the string.
and then he told us that the reflected wave equation will be $-Asin(\omega t+kx)$
Then he put the value of $t=0$, in both equations and the values he got wer... |
I'm curious about the physical meaning of the following equation:
\begin{equation}
\oint \mathbf{F} \cdot d \mathbf{s} = 0
\end{equation}
What does this physically mean? I think is has something to do with the chosen path of the particle but I'm not really sure. I have no experience with line integrals but looked up so... |
I have designed a simple inset-fed microstrip antenna, resonating at 2.45 GHz.
The transmission line model of the antenna reduces it to two radiating slots separated by a microstrip line, and it's precisely the surface current density in these slots that is responsible for radiation.
However, I encountered doubts when ... |
I'm studying principles of physics.
I have a question.
In my book, they seem to have calculated the Q value in different ways.
$$
\begin{align}
\rm p + {^{27}_{13}Al} &\rightarrow \rm{^{27}_{14}Si} + n
\\
\rm ^{13}_7N &\rightarrow \rm{^{13}_6C} + e^+ + \nu
\end{align}$$
In first example, they calculate Q = (26.981539 +... |
So i know we can get radial velocity by measuring blue shift and then we can use the distance to the star and its proper motion to get its tangential velocity. In the case of Bernards star, its expected to approach within 3.75 light years in 11800 years. How is the trajectory of the star calculated or plotted using jus... |
Apologies in advance if this has been addressed before... it's something if a daily puzzle during my morning ablutions and I haven't gotten a handle on it yet.
Consider the hot water pipe from my basement to second floor sink. Between uses this cools to ambient temperature; call it 15 degrees C.
When I turn on the hot ... |
As I understand particles are localized fields (16fields+g). Can you explain on hydrogen atom example that moves in space vacuum. Does it really moving, or it is continious field disturbance interaction that travels in space time since BB inflation. As analogy with 2D water wave. Does matter fundamentally travels or it... |
Let’s say you have a planar soap film, which thickness increases linearly. If you burst it, the film will retrace and the retracing speed will decrease. How exactly does the velocity of bursting depend on the film thickness? I need to find the equation describing this kind of retraction.
|
I think if curl of a vector field v corresponds to an applied rotation, it's cross product with a velocity vector field w (say) should give something analogous to the resulting torque. Am I close?
|
When calculating the self-energy correction of a massless quark up to one loop, I get
$$i\Sigma(p)=i\frac{\alpha_s}{4\pi}C_F/\!\!\!{p}\left[\frac{1}{\varepsilon_{\text{UV}}}-\gamma+\ln(4\pi)+1+\ln(\frac{-\mu^2}{p^2})\right]+i/\!\!\!{p}\delta_2.$$
I assume it is easier to work with the on-shell (OS) scheme, since the di... |
I am reading this paper regarding cornea phantom sensing using THz radiation.
In this paper, the authors propose using a bunch of modelling and to measure a bunch of spheres of different radius of curvature (RoC) to compare to the the results obtained from measuring an imperfectly hemispherical sample.
It is stated in ... |
I'm doing an experiment where I'm trying to determine the conductivity of a material by putting a sample rod in the center of a coil which is a part of an RLC circuit with an AC generator.
I was told by certain professionals in the field that putting the rod inside the coil will have an effect of extra resistance in th... |
If a passing star can jostle comets in the Oort Cloud, why doesn't the Moon disrupt the orbits of high-flying satellites?
Or does it? Maybe the satellites need periodic course corrections?
|
For simplicity, I only calculated half of the commutator. I didn't leave everything in components because I'm uncomfortable considering
(I previously messed up the indices. The following is the corrected version by Sean)
\begin{equation}
\begin{split}
\nabla_{V^i e_i}(\nabla_{W^je_j}X^k e_k)=\nabla_{V^i e_i}(W^j (\part... |
I'm trying to make sense of how the fresnel equations apply to metals. Here are a few of the things I believe I understand:
All reflections of light occur specularly. When an object appears to reflect diffusely, this is because at a microscopic level, the surface is rough and so the light is being specularly reflect... |
Following Peskin & Schroeder's Sec.7's notation, I would like to compute the matrix element
$$
\left<\lambda_\vec{p}| \phi(x)^2 |\Omega\right>\tag{1}
$$
where $\langle\lambda_{\vec{p}}|$ is obtained by boosting the state $\langle\lambda_0|$ whose momentum eigenvalue is zero i.e. $\langle\lambda_0|\vec{P} = 0$ while its... |
I have zero experience with lidar systems, but I have been under clear water and looked up at the interior/ceiling of an indoor pool, and even the slightest turbulence at the surface distorts what I see to a greater extent than anything I look at underwater.
I do realize that laser light is more coherent than regular v... |
Like in the case of a gridded ion thruster, the positive ions are accelerated due to their attraction to a negatively charged gird at the back end of the thruster. Why don't the ions just stay by the grid? How are they ejected out of the back at high speeds? Do the ions simply have a high oscillation amplitude, and are... |
In Chapter I.7 of "Einstein Gravity in a Nutshell", Zee introduces the concept of covariant derivatives. I am confused by the first line in this section (see below) as it appears that we can represent any vector field in a 3 dimensional euclidean space by $\overrightarrow{W}(x) = W^\mu(x)\overrightarrow{e_\mu}(x)$ wher... |
I am wondering why reflected rays are not considered with lenses. If a ray strikes a surface, another is reflected off that striking point; however, this is not added when studying lenses, only refracted rays are considered.
Is there any law which gives the ratio of reflected and refracted rays with lenses?
|
I realized that enthalpy is defined as the total "energy content" of the system. Given that in Hamiltonian mechanics we also deal with the total energy H = T + V, can we somehow use Hamiltonian mechanics (or some modification of it) to solve thermodynamic problems?
For eg, H = U + PV, can this equation be dealt with Ha... |
Given,
\begin{equation}
T^{\mu\nu} = F^{\mu\lambda} F^\nu{}_{\lambda} - \frac{1}{4} \eta^{\mu\nu} F^{\lambda\sigma} F_{\lambda\sigma}.
\end{equation}
Here $(T^{\mu\nu})$ is the energy-momentum tensor of electromagnetic fields.
Staying in four-dimensional tensor notation, demonstrate that the tensor obeys the energy... |
At least naively, there seems to be a tension between two seminal works on the stability of Minkowski space.
In Witten's A New Proof of the Positive Energy Theorem, in the section "Semiclassical Stability of Minkowski Space," Witten considers the vacuum Einstein equation of $R_{\mu \nu} = 0$ and an asymptotically Eucli... |
I have two electrons X and Y.
In Y's rest frame, X is approaching it radially from infinity with, say, 70% the speed of light. I want to know what the radius of the classically forbidden region is for electron X, in Y's rest frame.
I know that a classically forbidden region is when the total energy of a particle is les... |
I have a "philosophical" question regarding the use of periodic boundary conditions (PBD) in modeling and simulating systems of particles.
Let us consider a system of $N$ classical particles whose dynamics is described by Hamilton equations with the following Hamiltonian:
$$
H(\boldsymbol{x}_1,...,\boldsymbol{x}_N,\bol... |
I stumbled upon the following question in a textbook. The direct translation would be, for a potential:
$$
V(r)=\frac{\alpha}{r^2}
$$
perform partial wave analysis. What I assume this means is, use partial wave expansion to find $\delta_l$, the scattering phases and $\sigma_l$.
Both are directly connected via:
$$
\sigm... |
I know that water can exist in various states (liquid, solid, ...) and can be in various places (clouds, oceans, ground, ...). What I want to know is whether or not the total number of water molecules on planet Earth is steadily increasing or decreasing and why? For example, is the amount of water now on planet Earth... |
The expected energy in the canonical ensemble is given by
\begin{equation}
\begin{split}
\langle E \rangle &= \frac{\displaystyle\sum_{i=1} E_i e^{-\beta E_i}}{\displaystyle\sum_{i=1} e^{-\beta E_i}} \\
&\hat{=} \frac{1}{\mathcal{Z}} \displaystyle\sum_{j=1} E_j g(E_j)e^{-\beta E_j}
\end{split}
\end{equation}
Here... |
The Wikipedia page about the optical equivalence theorem mentions that, if we denote with $f_{\Omega}(\hat a,\hat a^\dagger)$ an "operator that is expressible as a power series in the creation and annihilation operators that satisfies the ordering $\Omega$", then "the quasiprobability distribution associated with $\Ome... |
I've been studying Talagrand's What is a Quantum Field Theory? lately and I have some questions regarding the scheme he presents.
Essentially the state of affairs as of where I am in the book is that if one wants to model a certain type of particle, one finds a suitable representation of the Poincaré group (and all the... |
Recently my teacher asked me to create a Fresnel zone plate (Fresnel lens to be accurate).
I wanted to print it using a laser printer with a resolution of 1200*1200 dpi. I know that i should block even or odd zones in order to focus the light. The problem is using r_n = (f * z * n)^(1/2), the zone radiuses are so small... |
EDIT: This is a more precise version of an old post Classical Theory explanation of Compton Effect by someone else.
Standard textbooks explain the Compton effect using the notion of photon. It is always stated that the classical theory fails to explain the experiment. In fact, Compton in his original paper "A quantum ... |
The normal diagram used to explain gravitational lensing shows a two-dimensional plane that is deflected by a heavy weight. This is a two dimensional description that requires an extra dimension to complete it. My question is does real three dimensional space require an extra dimension to explain gravitational lensing.... |
I'm currently reading arXiv: 1703.05448 [hep-th]. In this question, I'm interested in a statement made on page 67 of the pdf (76 of the printed book, if you prefer to check in it). There, the author says
Supertranslations transform one geometry into a new, physically inequivalent geometry, despite the fact that they a... |
I have an enclosure running an ON/ OFF temperature control system. The below graph shows internal air temperature over time. I have the raw data providing actual values.
I have the dimensions of the enclosure, I know its material of construction, and I know the external air temperature over the duration of the system's... |
There have been previous questions on this, for example see this and this question, but my question is different.
I get that in 2+1D, mathematically speaking, exchanging two identical particles twice may not be equivalent to not exchanging the particles. All good. But since we do not live in a 2+1D world, but actually ... |
I am deriving an equation modelling a magnetic guitar pickup and I am stuck.
I am trying to derive based on a paper for guitar pickups and it uses a magnetic masses method to find the magnetic flux at point c from magnetic field generated by point a and steel point b. I am confused where the integral comes from:
These... |
I was reading the Wikipedia page on Proca Action. To summarize, it is almost like Maxwell action, but with a mass term because of which Proca action does NOT have gauge invariance. From the equation of motion, we see that each of the 4 modes obey Klien Gordon equation, and they also obey a "Lorenz gauge" condition $\pa... |
Two square conductors with neutral charge and surface $A$ and $d<<\sqrt{A}$.
The conductor in the middle is the same shape but with a very small hight, $dh$, and is charged with $q$
How to determine the charge distribution on each of the edges of the conductor?
I know the E field on the edges of the middle conductor $... |
I am having a hard time understanding the physical meaning of asymptotic symmetries in General relativity. I think I understand the mathematics, but the meaning eludes me. I'll try to write the things I do understand, with an emphasis on an analogy with electromagnetism, and then I'll ask what I don't get.
Gauge symmet... |
There is a reason to the question but I don't think the stack exchange will allow me to give it. It would be proposing a personal theory, which is not allowed. But we are allowed to ask speculative questions so I think the question should be allowed to stand as it is.
This is, by the way, close to the critical density ... |
Here is the definition I know:
$V(\vec r)-V(\vec r_0)=\int_{\vec r_0}^{\vec r} -\vec E \cdot\vec dr$
I have lots of problems with this topic. How can I choose the starting point? and does it matter where? I see in books that sometimes we can write $\vec r_0=\infty$ so that $V(\vec r_0)=0$, because for a finite charge,... |
I found a nice text about the illumination of the sky with respect of the position of the Sun
https://www.brikbase.org/sites/default/files/ies_030.pdf
where I could find the following formula:
What I would like to have explained are:
IO and M values.
Could it be possible?
|
In Nolting's QM book (Theoretical Physics 7), in the chapter on central potentials, a radial momentum operator $\hat{p}_r$ is defined as
\begin{equation}
\hat{p_r} = -i \hbar \Big( \frac{\partial}{\partial r} + \frac{1}{r}\Big).
\end{equation}
In two following problems, we try to find the conditions satisfied by wave f... |
I have seen the total energy of a system, $E$, given in two forms:
$$E = K + U$$
where $K$ is the kinetic energy and $U$ is the potential energy, as well as
$$E = K + U + I$$
where $I$ is the internal energy.
Is it correct to always view the internal energy as part of the potential energy? Or is this simply a matter of... |
Say I have two points on the surface of a sphere $p_1$ and $p_2$. To each point, I have two unitary vectors $v_1$ and $v_2$ (not necessarily tangent). I want to find the alignment between $v_1$ and $v_2$. I understand that I can't just take the scalar product $\langle v_1, v_2 \rangle$ as I am in a curved geometry. So ... |
If we design a setup similar to Michelson Interferometer but with one mirror only. So, there is an angle between the 2 rays to the detector. Will we get an interference pattern on the screen?
|
https://ui.adsabs.harvard.edu/abs/2014cosp...40E1114G/abstract#%3A~%3Atext%3DIt%20was%20shown%20statistically%20that%2Ccomparison%20with%20quiet%20geomagnetic%20conditions
This study says that on average, rates of heart attack and brain stroke increased by an average factor of two(!) during geomagnetic disturbances. Ge... |
I've looked on-line for a simple treatment of springs under tension/compression while moving at relativistic velocities parallel to the direction of tension/compression and could not find one. There have been several recent posts involving springs and special relativity and I wanted to make sure I understand. I have a ... |
Let a particle with a mass $m$ and a charge $q$ move with a speed $v$ close to the speed of light ($v\approx c$). Then, the special theory of relativity tells us the particle's relativistic mass would increase in a factor $\gamma = \frac{1}{\sqrt{1-(v/c)^2}}$. Nonetheless, the particle's charge would not be modified (a... |
What happens to the repulsive force between two electrons, once one of the electrons travel at relativistic speeds?
Let's consider two electrons in an atom with magnetic dipole moment, one of which is travelling at relativistic speed $v\sim c$. If electrons were stationary in a reference frame $S$, one could use Coulom... |
I'm going through the section on generalized Langevin equation (Chapter 15) in Mark Tuckerman's textbook Statistical Mechanics: Theory and Molecular Simulation, and there is a property that I am struggling to prove: that the force (eqn 15.2.11)
$$
R(t)=-\sum_\alpha g_\alpha\left[\left(x_{\alpha0}+\frac{g_\alpha}{m_\alp... |
The product $\omega t$ is a dimensionless quantity and the same is true for $\sin{\omega t}$. If they are dimensionless, then they are identical between the rest and relativistic frames because there is no dimensions of time or length to dilate or contract.
This represents a circle rotating about a fixed center with $\... |
A very fundamental equation in understanding fluid flow is $Q = \Delta P / R$. When the flow is through a cylindrical pipe of constant radius, $R=8\eta L/\pi r^4$ can be substituted to give Poiseuille's Law. This is basically the first think you learn after Bernoulli's Equation. However, I cannot remember the name of t... |
A complex refractive index is defined as $n = n_0 + \kappa$ where $n_0$ is the "standard" refractive index, and $\kappa$ is the optical extinction coefficient. The optical extinction coefficient "indicates the amount of attenuation when the electromagnetic wave propagates through the material". The larger the value, ... |
I've recently read Feynman's QED in which he mentioned the possibility that the seemingly random numbers that correspond to the mass of the electron and heavier charged particles (mu and tau electrons) could be the result of something even smaller making up and governing their mass. Is there any theory or experiment th... |
The Schwarzschild metric represents a stationary (and static), spherically-symmetric, spacetime. These characteristics are manifested by the four Killing vector fields: one for time translation and three for rotational symmetries.
Inside the horizon, however, the time coordinate (and its associated Killing vector fiel... |
I am trying to deep dive and study the isotropic Schwarzschild coordinates, whose line element is written for particles lying onto the equatorial plane $\theta=\pi/2$ as:
$$ds^2 = -\left(\dfrac{1-\dfrac{R_s}{4r'}}{1+\dfrac{R_s}{4r'}}\right)^2c^2 dt^2 +\left(1+\dfrac{R_s}{4r'}\right)^4 \left[dr'^2 + r'^2 d\phi^2\right].... |
My confusion arose while studying two dimensional models of quantum gravity, in particular the well-studied Jackiw-Teitelboim gravity model in the holographic context. Is it correct to say that the JT gravity model is a theory of dynamical gravity? My naive understanding is that in two and three dimensions there are no... |
suppose I'm given the co-efficient of friction of a surface where the normal force of a block is equal to $mg$ and the block is at rest. Now will the friction force change over time if I displace the block from it's initial position to a distance $d$? or it will be kinetic friction co-efficient*mg throughout the path
|
Could someone explain Holsapple's simple scaling law?
Furthermore, is Holsapple simple scaling law able to be used on Earth in the context of dropping an object and measuring the impact crater size?
Lastly, I’ve seen this equation, but I’m not sure if it’s a correct simplification of the law
$\displaystyle D=A \left( \... |
When we convert a galvanometer into an ammeter we connect the resistance in parallel, the only reason we connect a resistance in parallel with galvanometer is so less current passes and the flow of current through galvanometer is slower but the same could be achieved with resistance in series.
|
I have read that a very large number of partial waves around 200 and a large matching radius of 300 fm is required to obtain the cross section in Coulomb excitation. This is certainly far greater than normally being used. Why are these values so high. 1. How does one arrive at the maximum number of partial waves (or ... |
In Weinberg's QFT volume 1, section 2.2 and appendix 2.B discuss the Lie group symmetry in quantum mechanics and projective representation. In particular, it's shown in the appendix 2.B how a representation of the Lie algebra extends to a representation of the group in the neighborhood of the identity. Unfortunately I ... |
I was reading a book to understand the limits of the euclidean space I understand that lines that are parallel in 2d can meet in 3d space like on a sphere but it is hard to imagine or fathom why the deviation in the angle is happening
what I deduced is is that the 2d space of the sphere is actually curved so what appe... |
This might be a stupid question or has already been asked before, so please refer me to the answer if it has.
Let's say we have a rolling ball, which is purely rolling, and there is no friction. (Is that even possible?) What I'm having trouble with is that the total kinetic energy of the ball is the translational kinet... |
Consider a bipartite quantum system described by the density operator, $\hat{\rho}$, an operator acting on the Hilbert space $\mathcal{H}=\mathcal{H}_{A}\otimes\mathcal{H}_{B}$. This matrix will be a vector (that in quantum physics is denoted with a double bra or ket $|\rho\rangle\rangle$) in the Liouville space, $\mat... |
A gradient $\nabla \rho$ in the density field $\rho$ of fluids at thermodynamic equilibrium is suppressed at a rate given by $D \nabla^{2} \rho$, allowing to measure the diffusivity $D$ of the fluid from the linear map between the density gradient and the rate of gradient suppression $\partial_{t}\rho\sim \nabla^{2} \r... |
Is there any possible way to trap atoms that are 'hot' and the trap itself doesn't cool them, but instead can continue to trap the atoms even at high temperatures? Where hot is defined as temperatures close to room temperature (ie 200-300 K).
I am aware that most traps operate at nK temperatures and then many traps (op... |
The uncertainty principle is confusing me. Considering this image from the article:
Is the particle believed to be physically moving with similar capriciousness in real space; and if so, what physically causes it to do so? (Some fundamental property of nature, a result thereof at small scales, the high energy of the p... |
We have two places, call them Here and There where a particle could be. When the particle isn’t spatially superposed we write its state as $ |1\rangle_{Here}\otimes|0\rangle_{There}$ zero being the vacuum mode.
My question is why when the particle is superposed, for example in the state $$\frac{1}{\sqrt{2}}(|Here\rangl... |
I am working with an effective model describing an exciton-polariton system. I need to solve the Schrödinger equation (eigenvalue problem). To describe the presence of losses the diagonal terms are complex and also the parameters multiplying the first and second order derivatives of the differential equation system. Th... |
I know that particles in QFT are just excitations of its corresponding field. But is it possible to have a field which cannot generate particles?
If yes, what terms must be added to the Lagrangian so that particles can be created?
|
So I have always been passionate in physics but recently I began to take a greater interest in learning more than the curriculum of my age. I have a significant theoretical understanding of quantum physics and mechanics yet my technical ( as in terms, constants and formulating equations) knowledge is far from sufficien... |
Imagine a world where polaroid filters have somewhat strange properties, in such a way that this is impossible or very hard to know. The inhabitants use polaroid filters to determine what polarization photons have. The logic is kind of circular, they assume that polarization filters have symmetrical probability distrib... |
A couple of days ago I encountered a problem on special relativity. It said
There are 2 observers A and B. B is emitting $k$ balls per unit time per unit angle from it in all directions from its perspective. The speed of those balls are $c=$ speed of light, and the B itself is moving with respect to A at a speed of $v... |
Assuming I have a homogeneous solution such as salt in water. My intuition tells me that gravity or centrifugal forces would affect sodium ions more than water molecules. Theoretically, if I could centrifuge salt water fast enough for the pulling forces to surpass the forces of the hydrogen bonds between salt and water... |
A particle with mass $m_1=m$ moves along the x-axis at a velocity of $v_0$ and collides with another particle $m_2=4m$. As a result of the collision $m_1$ travels upwards at an angle of $90 ^\circ$. (see diagram)
How can I find the velocities after the collision?
My approach with conservation of momentum and kinetic e... |
How would one simplify the expression
$\gamma^0 {\not}p \;\gamma^0$
?
My guess would be that its
$$\begin{align}
\gamma^0 {\not}p \;\gamma^0&=\gamma^0 \gamma^{\mu} p_{\mu} \;\gamma^0\\
&=\gamma^0\gamma^{\mu}\gamma^0 p_{\mu}\\
&=\gamma^{\mu\dagger}p_{\mu}\\
&={\not}p^{\dagger}
\end{align}$$
|
Problem
Consider a Hamiltonian
\begin{equation}
H(c^\dagger, c) = \mu_1 c_1^\dagger c_1 + \mu_2 c_2^\dagger c_2 + U c_1^\dagger c_1 c_2^\dagger c_2\,,
\end{equation}
where $c_i$ are fermionic operators. Following e.g. Altland, Simons. Condensed Matter Field Theory, the partition function, written as a functional path i... |
I'm struggling to calculate the s-matrix elements for 2 photon scattering from a 2 level system. I'm trying to understand the difference between coherent and incoherent scattering and following the paper https://hal.science/jpa-00209720/document. So far I've been trying to use time dependent perturbation theory to try ... |
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