instruction stringlengths 31 24.3k |
|---|
I don't understand why exactly the notion of particles only makes sense in flat spacetime. From explanations I have read, it says that in general curved spacetime a unique vacuum couldn't be talked about as different coordinate systems used to describe the spacetime would imply different vacuum, messing up covariance.
... |
A banquet hall ($150 m^3$) is to be used for a formal dinner for 20 persons. Each person occupies $0.075 m^3$ of space and has an average heat transfer rate of $500 \frac{kJ}{hr}$. If the AC system fails, determine the increase in the internal energy and temperature of the air in the hall during the first 15 minutes of... |
In an inductor, back emf is induced as there comes flux change. It is said that back emf decreases as time passes (when inductor is just connected to DC source).
When back emf decreases current increases in inductor. Current increases flux associated with inductor.
Back emf comes obeying Lenzs law. (Back emf is to fig... |
The upsilon is an unstable particle that decays into a tau and an
antitau according to the reaction:
The upsilon is at rest relative to the laboratory when it decays. The
momemtum of the tau relative to the laboratory is $4.40GeV c^{-1}$.
The rest mass of the tau and of the anti tau is $1.78GeVc^{-2}$
Determine the r... |
The ergosphere is created because of the twisting of spacetime by a fast-rotating black hole.
Then what if we rotate a non-singular object (I mean just a normal object that is not a black hole) really fast? Can we create an ergosphere without a black hole?
And also in the ergosphere, it is known that negative energy is... |
I am creating a projector, for the purpose of explanation given I cannot take a photograph of my projected image, let's say I would like to project the following image:
The image I get however resembles the following:
That is to say the light seems to diverge more the further it is from the centre. My inclination fro... |
The Schrödinger equation is just another way of writing the conservation of energy, right? So how can you use it to find the quantum wavefunction? I mean in every example I've seen the wavefunction is calculated using sines and cosines so I don't see how you can use the Schrödinger equation to find a wavefunction. All ... |
When an electron moves at a high speed, it has a large kinetic energy.
I know that E = mc^2 and so if an electron was travelling at a high speed, wouldn't the mass decrease in order to increase the kinetic energy (as smaller masses travel faster)?
Where does the energy come from to increase the mass; if the energy cam... |
I made the surprising discovery that steam escaping a pressure cooker through a screw-valve on top of the pot feels relatively cool: I can comfortably place my hand on the steam without getting burnt.
The same thing does not happen when I heat water in a kettle: The steam there is live and dangerous.
Does this happen ... |
Let's say we have a QFT, which off-shell has a non-zero stress-energy tensor, but vanishes when the equations of motion are applied.
If the stress-energy tensor vanishes off-shell, then all field operators are necessarily spacetime independent. But what can we say about the fields spacetime dependence when it only vani... |
Two point charges are located on the $x$-axis, $q_{1}=-e$ at $x = 0$ and
$q_{2} = +e$ at $x = a$.
(a) Find the work that must be done by an
external force to bring a third point charge $q_{3} = +e$ from infinity
to $x = 2a$.
So i know we have to use (where $k$ is Coulomb's constant)
$$\sum_\ kq_{3}(\frac{q_{1}}{r_{1}... |
It seems that the Lagrangian of QED describing electrons and muons cannot include terms like that:
$$\overline{\psi_{(e)}}i\not\!\partial\psi_{(\mu)}$$
where $\psi_{(e)}$ and $\psi_{(\mu)} $ are 4-component dirac spinors describing the electron and the muon respectively.
I don't understand why this is illicite, as it s... |
Chirality is not conserved in propagation (e.g., electron oscillates between left and right chiral). But is chirality conserved in interactions? What is a good reference paper or book for this notion of chiral conservation (or not) in interactions?
As an example, in QED Bhabha scattering say a left-chiral electron and ... |
The top ball is then displaced along the cylinder by a distance d, while the bottom ball is held fixed. At t = 0, both balls are released with zero initial speed. Ignore any effects due to gravity.
What are the resulting equations of motion, x(t), for each of the balls, where x is the position of the ball along the cir... |
In Peskin's book, he first tackled massless $\phi^4$ theory, its renormalization, namely the Callan-Symanzic equation when m=0. And then he put the mass term in later and approach this term 's effect by new technics conducted in the session of "renormalization of local operator". I'm just quite confused the reason behi... |
What are the main differences in the path of light ray for different values of $k$ in the FLRW metric?
Is it possible to build an experiment (even a mental one) with a single light ray to distinguish which variant of the metric we live in?
|
Let's say we have a system with Hamilton equations
\begin{equation}
\dot{Y}^A = \Omega^{AB}H_{,B}
\end{equation}
where the coordinates are
\begin{equation}
Y^A=\big(q^i,p_j\big)
\end{equation}
where $i=1,\dots,N$ and $j=1,\dots,N$, $A=1\dots, 2N$, $H$ is the Hamiltonian of the system and $\Omega$ is a symplectic 2-form... |
What is the origin of radioactivity that appears sometimes in rivers close to a nuclear plant? (due to nuclear plant activity) ?
In particular, is it due to primary circuit that would contaminate the tertiary circuit ?
Or is it due to nuclear waste that is sent on purpose to the river once its radioactivity is lower to... |
I was solving the P. 2.41 of Griffiths' Introduction to Quantum Mechanics.
Nothing really new until I read a proposed solution (from Griffiths' himself) for the problem in which it states that I can write a function $\Psi$ which is a linear combination of the first three states $\Psi_0$, $\Psi_1$ and $\Psi_2$ as
$$\Ps... |
Consider a 2-body decay $M\to X+Y$. I am looking for the
distribution function of a particle $X$ by having the distribution of
a particle $M$.
To proceed, I start from the following equation:
$$
(p_{M}-p_{X})^{2} = p_{Y}^{2} = m_{Y}^{2},
$$
or
$$
E_{X}^{\text{M rest}} - \frac{E_{M}E_{X}-|\mathbf{p}_{M}||\mathbf p_{X}... |
It's written multiple times in my textbook that
Some molecules at the surface of the liquid have kinetic energy more than those in the bottom, so they can escape from the surface.
But what causes them to have more kinetic energy or more speed (as far as I understand more k.e means a higher speed)
My usual guessing to... |
An outlaw is escaping in a car traveling with a speed of $v_o$ in the positive $x$ direction (as measured form a stationary observer on the side of the road). A police officer, chasing in a vehicle traveling at a speed of $v_p$ also in the positive $x$ direction (as seen by the same observer), fires a bullet with a muz... |
Imagine a car standing on the road. Now the car starts to accelerate.
On the first part, the car accelerates from 0 m/s to 10 m/s.
Some of the fuel was used during this first part. let's call that amount X.
Now on the second part, the car accelerates from 10 m/s to 20 m/s.
Some of the fuel was used during this second p... |
A coherent source looses it’s coherence as it propagates, but an incoherent source gains coherence as it propagates. This 28 sec video illustrates this.This 28 sec video shows incoherent to coherent. Distant star light leaves the star as incoherent light but arrives in our telescopes as coherent light. Light leaves the... |
What is the relationship between the pressure of water and its boiling point? I am aware that a substance boils as soon as its vapor pressure equals that of the surrounding air. I have researched extensively and the best I could come come up with was rearranging the Goff-Gratch or Arden-Buck equations for temperature. ... |
If everything slowed down around you, but you were just as fast you are normally, would you jump higher? I am thinking velocity would increase, thus the force generated would be stronger, but I am not sure what physics say about this. What are the conditions that need to be true in order for the assertion to be true?
B... |
An image question got me today when I was reviewing image theory.
With 1 mirror -- I see 1 image out of phase of myself.
With 2 parallel mirrors, me being between them -- I see infinite images of myself.
With 2 mirrors at angle (let's say right angle) -- I see 2 out of phase images and 1 in phase image at the corner.
B... |
When reviewing the derivation of specific angular momentum for an angular momentum balance of the annular control volume of an impeller, ℏ , I have not been able to determine how the equation is derived:
ℒ /m = ℏ = ( ɽ X ν)
(specific angular momentum = cross product of position vector and velocity vector )
Shouldn’t t... |
I'm trying to compute the Lyapunov exponent for a smooth continuous time dynamical system(say, $\dot{\bar{x}} = f(\bar x)$). I using the QR decomposition method. Here are the steps that I follow.
Choose some initial condition in the basin of the attractor. Call this $\bar v_0$. And have a blob (hypersphere, $U$) of un... |
Assuming the cosmological constant is zero, the Einstein equations are:
$ R_{\mu \nu} -\frac{1}{2} R g_{\mu \nu} = 8 \pi T_{\mu \nu} $. Using the definition of the scalar curvature, we may obtain:
$ R = R^\nu_{\; \nu} = g^{\mu \nu} R_{\mu \nu} = \frac{1}{2} R g^{\mu \nu} g_{\mu \nu} + 8 \pi g^{\mu \nu} T_{\mu \nu} = \f... |
Every particle in the universe is moving in spacetime: a massive "still" one (in the 3D sense) is moving in a purely timelike direction, a massive "moving" one in a direction with both timelike and spacelike components (but obviously timelike in total), a photon in a lightlike direction. We even theorized the tachyons ... |
Forgive me in advance for not being 100% accurate in my explanation. I am not an electrical engineer, nor have I academically studied physics, algebra, or anything of the sort.
So without further ado:
Let's say if I have a saucer made out of a light ferromagnetic metal sheet...If I put a device in it that creates an el... |
When we want to draw the band diagram of a solid and we know the solid has point defects can we leave some 'columns' of the band diagram empty?
|
I was going through the following proof of Lorentz invariant Phase space (in Modern Particle Physics by Mark Thomson).
Could someone please help me understand how the equation in the box is valid? If we are differentiating $p'_z=\gamma(p_z-\beta E)$ with respect to $p_z$ then why do we treat $\beta$ and $\gamma$ as co... |
Say im trying to prove $\frac{\partial \dot{T}}{\partial \dot{q}^i} - 2\frac{\partial {T}}{\partial {q^i}} = - \frac{\partial {V}}{\partial {q^i}}$ from the Lagrangian equation: $L = T - V$, and the euler-langrange equation, where $T$ is the kenetic energy and $V$ is the potential energy.
Below I have attached what I c... |
In what media the speed of visible light is slower than the speed of radio waves, if any?
Particles can be faster than visible light, but other electromagnetic waves?
|
I have always thought that current has the same definition as the ampere.
When this problem comes up:
So I instinctively choose answer A. But according to the my book, B is the answer?!?!
But why? Isn't current the number of electrons that flow through a given point per second? So does this mean that current and amp... |
I have the gain plots of a transmitting and receiving monopole antenna as shown in the image below. The axis of both antennas are coincident thus using the Friis Transmission Equation gives zero received power. In reality, would the power received be non-zero and is this caused solely multipath effects (eg path in oran... |
Please do provide assurance of what formula you used and that you did the calculations for the answer. Thanks.
My back of letter calculation says that CMBR was never in visible range since it became free from the opaque universe and that the point when it could be used to boil water is still far in the future.
Please c... |
I am trying to expand the flat-space action
$$
S_{BI} = -T_p \int{d^{p+1}} \sigma \ \mathrm{Tr}\left( e^{-\phi} \sqrt{ -\det(\eta_{ab} + 4\pi^2\alpha^2 \partial_a\Phi^i\partial_b\Phi^i + 2\pi \alpha F_{ab}) \det(Q^{i}_{j}) } \right).\tag{1}
$$
After some manipulation, I want to use the power series expansion of the n... |
The only quantity that appears after doing a Feynman path integral evaluation is the propagator which is used to compute different observables. The paths in the FPI don't appear anywhere in the calculation of an observable. Moreover, lots of irritation/paradoxes arise when one takes the paths in the FPI literally.
|
For circular motion to happen we need a centripetal force or acceleration i.e. a force perpendicular to the direction of motion at all instants. So without any perpendicular component of force circular motion will not occur.
Does the above statements mean that the circular path is a resultant path of the given velocit... |
I want to take the functional derivative of an integral with a d'Alembertian Operator:
$$ \frac{\delta }{\delta F(x)} \int d^4y\,G(x) \partial_\mu \partial^\mu F(y) $$
I believe this is related to the product rule (or integration by parts) and tried the following:
$$ \partial_\mu \partial^\mu (F\cdot G)
=\partial_\mu ... |
In Griffiths’ Introduction to Electrodynamics, he asks what changes would need to be made to Maxwell's equations to accommodate the existence of magnetic monopoles. Now, it is clear to me that the Gauss’s law and Ampere’s law must be left untouched. I also understand why the divergence of $\vec{B}$ should be $\alpha_{0... |
I have been thinking about what would happen if by chance the photons collided with each other. I heard once that electromagnetic waves pass through each other without any interference.
I wanted to know if I am correct?
Does the collision produce sound?
|
I am making a billiard game and need to push white ball to move other balls which should pocket so I need to calculate the force. I have mass, friction, distances, angles, collision point, origin point and destination point
How can I calculate the needed force to push the ball to reach the specific point in a 3D world... |
Are there solutions of the Schrödinger equation that are not a linear combination of separable solutions and how do we find them?
In Griffiths, Quantum, Prob. 2.49, there is a solution of the (time-dependent) Schrödinger equation, which reads
$$
\Psi(x,t)=\left(\frac{m\omega}{\pi\hbar}\right)^{1/4}\exp\left[-\frac{m\om... |
One of the propsed ways to reduce skin friction drag is by maintaining laminar flow. But to do this normall requires a low Reynolds number. But a low Reynolds number is in itself a recipe for extra drag.
This concept is meant to allow laminar flow at high Reynolds.
It removes the slowest part of the boundary layer by ... |
This is a very basic question in optics: why the mathematical language we use corresponds to what we actually see.
There are (at least) two ways to think of a decomposition of a visible light.
One way is experimental: when a beam of light passes through a glass prism it decomposes to many beams according to their color... |
I have a finite element model of homogeneous conductor in electricity with stable voltages setting. For simplicity, the conductor is in 2d dimension and a round shape. The boundary is insulated. I set some vertices with pre-defined potentials.(The red vertices are in 1 voltage and blue vertices in zero).
My problem is... |
I am trying to understand problem 3.4 in Griffiths' Introduction to Electrodynamics:
Prove that the field is uniquely determined when the charge density is given and the potential $V$ is specified on each boundary surface. Do not assume the boundaries are conductors, or that $V$ is constant over any given surface.
I'... |
We all know that faraday law mathematically states:
$$ V = - \frac{\partial \phi_B }{\partial t}$$
But I think this law is a bit weird because it says that the voltage developed across any conductor due to changing flux is same.. which is a bit counter intuitive for me. I mean, is there no dependence of how the materia... |
For my course in General Relativity I am given the problem to find the expressions for the gradient, laplacian, divergence and curl in spherical coordinates using covariant derivatives.
I have tried multiple ways to arrive at the answer but I have yet to find an answer that I can fully understand.
Here is what I tried,... |
When a person walks (assuming the feet don't slip), the ground is pushed backward by the foot while the force of static friction opposes the force and the foot remains stationary while the upper body moves. - This is what I've understood.
However, the upper body moves - I believe, since the foot exerts a force backward... |
C. Y. Lo says:
"According to Newton and Einstein, gravitation is independent of the temperature, but experiments show that the gravitation of a metal is reduced as temperature increases. ~~~. "
http://meetings.aps.org/Meeting/APR19/Session/H11.9
What is the experiment mentioned by the author?
If anyone knows that excep... |
Why does a neutron get ejected when Aluminium-27 is hit with an alpha particle?
It seems like:
Al-27 + He-4 --> P-31 (stable) and a gamma/(s) as the nucleus re-arranges. So why eject the neutron and go to the unstable P-30, which then decays by beta+ via:
Al-27 + He-4 --> P-30 + n?
If it helps, this is the context of 6... |
Do protons and electrons lose energy due to radiation?
Which one loses more energy, and why?
|
When you solve the Schrödinger equation for the classic particle in a box you get that $$\psi=\sqrt{ \frac{2}{l}} \sin{(\frac {n\pi x}l)}$$
where $x$ is the length from the leftmost point of the box, $l$ is the length of the box and $n$ is an integer where $$n=\sqrt{\frac{El^2}{\pi^2}}$$($E$ is equal to the energy in t... |
For the sake of this question, let's say I were the secret service, and wanted to install a system of magnets that could disable the weapon of someone in the oval office. This should be able to target the weapon of an adversary without affecting the weapons of the secret service agents in the room or preferably, any el... |
in particular, if the distance is more than about 1 fm?
|
I was recently taught about the expectation values of observables (Hermitian operators), namely that they are always real. I am wondering about non-Hermitian operators that have complex expectation values (and I know that that notion does not make "physical sense", but never mind). For example, there are the ladder ope... |
I was introduced the generator of Galilean boost $K=mx-pt$.
I was given an Hamiltonian with several particles: $H=\sum_i \frac{p_i^2}{2m_i}+V(|x_i-x_j|)$ where the potential only depends on the relative position between the particles.
I was asked to compute the poisson brackets $\{K,H\}$ and show that the general time ... |
I am building a homemade VDG generator and it does not seem to provide any electrical charges. My construction is as follows:
The top roller is PVC, it is "pierced" (I don't know the phrasing, sorry) by an aluminum shaft over two standing acrylic boards. They are connected with some stainless steel bolts and nuts.
The... |
Like many people, I've been chasing down idle curiosity, trying to get a better understanding of how certain particles interact with each other.
I have been particularly unsuccessful in trying to pin down what happens when an anti-down quark and an electron collide. Many of the other interactions I've looked into have ... |
$$\mathbf{B}=\begin{cases}
B_{0}t ;t \in [0,T]\\
B_{0}T ;t>T
\end{cases}$$
Assume negligible resistance for the connecting wire and other necessary constants.
Should I use Faraday's Law or Kirchoff's Voltage Law? I tried both of them end up with different answers. Also I assumed the area of the loop to be A in the cas... |
My middle school daughter became fascinated after reading the article below about how the matter/anti-matter balance of neutrinos helped create the big bang, so decided to make it her term research paper topic for science.
https://www.nytimes.com/2020/04/15/science/physics-neutrino-antimatter-ichikawa-t2k.html
Excerpt ... |
I have this generating functional
$$ Z(J)=\int \!D\varphi(x^\mu)\, e^{ i \int\!d^4x\,\left\{\tfrac{1}{2}\left[(\partial\varphi)^2-m^2\varphi^2\right]+J\varphi \right\} } ~~.$$
I am using Zee and he uses a trick to solve this integral by imagining discretizing it (page 22.) I don't want to use the trick, I ... |
Under the framework of resource theories like entanglement, asymmetry, athermaility, etc, a set of operations $\mathcal{O} \subset \mathcal{B}(\mathcal{H})$ is chosen (e.g., LOCC) due to physical limitations, which corresponds to a set of free states $\mathcal{F} \subset \mathcal{S}(\mathcal{H})$ (e.g., separable state... |
In this paper https://arxiv.org/abs/1211.6442 they compute the stress-stress correlation function for a Chern insulator by using a Feynman diagram with a Fermi loop and an ingoing and outgoing "graviton" corresponding to the stress tensor (equation 98). What I am wondering is, if I wanted to compute this in the case o... |
What is the closest thing we have to a 'black-body' bolometer?
What are the best absorptive bolometers made of?
|
Consider a Fokker-Planck (FP) equation where the advection term is a function of time, i.e.
\begin{align}
\frac{\partial P ( x , t )}{\partial t}
=
-\nabla \cdot \left[ -\mu \, P \, \nabla U (x,t) - D \nabla P \right]. \qquad\qquad ({\rm I})
\end{align}
Q1 Are there general steady-state distributions (ie $\partia... |
I was reading my freshman physics textbook (fundamental's of physics by Jearl Walker), and the book says that Newton's first law only applies in a special frame of reference
Newton’s first law is not true in all reference frames, but we can always find reference frames in which it (as well as the rest of Newtonian mec... |
If a black hole accelerates a hypothetical stick near the speed of ligth the stick will tend to reduce its length but does it mean that if the distance between atoms of that stick changed, accelerations of different parts of the stick were of different?
|
I am trying to better understand the Lorentz Transformation on a fundamental level and gain some intuition of it. In the Lorentz Transformation, the derivative of x' with respect to x must be a nonzero constant. We know that it is nonzero because spatial coordinates are correlated between reference frames (that is to s... |
We see an object when light from a source strikes the object and then reaches our eyes. How does light, which is an electromagnetic wave, gets encoded with the information about the object? Do the individual photons get encoded with this information or is it the wave nature of light that gets modified to carry informat... |
I have been trying to compute, without much success, the following Fourier transform in 4-dimensional Minkowski space
$$
I=\frac{1}{(2\pi)^4}\int d^4 k \,\frac{e^{ik\cdot x}}{k\cdot v},
$$
where $v^\mu$ is any constant vector. $v^\mu$ would be spacelike in my case, if that's helpful. Do you have any ideas on how to do ... |
During an adiabatic process there is no heat exchange and thus, q = o.
During a free expansion no work is done and so w = o.
Since q = U + w, thus we can say that during the overall process, change in internal energy is also 0.
And since in an ideal gas, internal energy energy only depends on the kinetic energy, and K.... |
I was studying a qft text when this equality was taken for granted. When I try to do $p\rightarrow -p$ by hand, I get an overall factor of $-1$ from the differential. How is this justified?
$$\phi(x)=\iiint_{-\infty}^\infty \frac{d^3p}{(2\pi)^3} \frac{1}{\sqrt{2p^0}} (a_{\vec{p}} +a_{-\vec{p}}^\dagger)e^{ip\cdot x} = ... |
Under what conditions can you just add velocities? For example if I throw a paper ball in the air in a 1m/s wind the ball should move in that direction at 1m/s as it falls according to relative velocities. However what if I throw a bowling ball like this, common sense says it will just fall straight down, why doesn't ... |
I have difficulties to apply Wick's theorem to the following problem-set:
We have three free scalar fields $\phi_1, \phi_2, \phi_3$. While the field $\phi_3$ has the mass $M$ while $\phi_1$ and $\phi_2$ are massless. With the interaction Hamiltonian:
$$
H_{int} = \frac{\lambda_{3333}}{4!}\phi_3^4 + \frac{\lambda_{3111... |
I'm a high school student, and I have a question about the mass defect.
I learned that when nuclear reaction occurs, the total rest mass (or rest energy) of reactants is greater than that of products, and the missing rest energy is released as a form of kinetic energy etc. But considering the fact that those reactants ... |
In curved spacetime, the spacetime interval $ds^2=g_{ab}dx^a dx^b$ between two infinitesimally events $(t,x^i)$ and $(t+dt,x^i)$ happening at the same space point w.r.t an observer is given by $ds=\sqrt{g_{00}}cdt$ since $dx^1=dx^2=dx^3=0$. How is the proper time interval $d\tau$ equal to $d\tau=\sqrt{g_{00}}dt$? How d... |
Say a conductor is grounded and its potential is $0$. Now if we bring other charges near this conductor, they may cause the conductor to have a certain net non zero charge with the potential on the conductor remaining the same.
From where does this conductor gain this charge? And how does the conductor manage to spread... |
As far as I know, monochromatic waves are waves in the form: $$\vec E(\vec r, t) = \vec E_o \cos(ωt − \vec k \cdot \vec r)$$ where $\vec E_o$ is a constant. Note that this waves are a subset of the plane waves family.
However, in this question: Is a plane wave necessarily monochromatic?, I read that there are monochrom... |
Let the position of a particle be given by the vector:
$$\vec{r}=(2t-t^2) \vec{e_{x}} +(8+6t)\vec{e_{y}}$$
where $t$ is the time, starting from $0$.
When solving for the distance the particle has traveled from $t=[0.0 ; 2.0] s$, my teacher said it was equal to the displacement since:
$$s= \parallel\vec{r}\parallel = \s... |
I am currently following the book of Lowell.S.Brown.
In the book, we construct:
$$|\zeta\rangle = e^{\alpha^{\dagger} \zeta} |0\rangle \tag{2.4.38}$$
Now, to show that the states so constructed are coherent states, we apply the destruction operator to it:
$$\alpha |\zeta\rangle =\alpha e^{\alpha^{\dagger} \zeta} |0\ran... |
Shouldn't these photons create a stronger photon when they collide? If you shine a light at another light it gets stronger not destroyed. Why is it different in the Casimir effect case?
|
If we imagine a lightwave moving through space without considering how the space is deformed due to the energy and momentum of the light, we would find it redshifted once we take GR into account correct?
Is it then correct that if we instead had a massive particle moving through space without taking GR into account, we... |
When resonance occurs, there is a maximum transfer of energy from the driver to the forced oscillator. This means that the damping system should have the same frequency as the forced oscillation because then, the maximum transfer of energy will be from the driver to the damping system.
However, this also doesn't make s... |
I have phonon dispersion curves for a crystal with two atoms per unit cell.
The following figure is phonon dispersion curves for the same crystal as above. $q_{BZ}$ denotes the wavevector at the BZ boundary. The direction of $q$ is antisymmetric, so the LA, LO branches are doubly degenerate. LA/TA, LO/TO denote longitu... |
I am following these (http://edu.itp.phys.ethz.ch/fs13/int/SpinChains.pdf) lecture notes and I can't understand why given the following XXX Heisenberg hamiltonian
$$
\mathcal{H}=\frac{J N}{4}-J \sum_{i} \left(\frac{1}{2}\left(S_{i}^{+} S_{i+1}^{-}+S_{i}^{-} S_{i+1}^{+}\right)+S_{i}^{z} S_{i+1}^{z}\right),
$$
then,
$$
\... |
In this paper: A. Y. Kitaev, "Unpaired Majorana fermions in quantum wires", Phys.-Usp. 44 131 (2001), arXiv:cond-mat/0010440, it says:
Unlimited quantum computation is possible if errors in the implementation of each
gate are below certain threshold. Unfortunately, for conventional
fault-tolerance schemes the threshol... |
I don't have training in physics (so forgive me if I use the wrong terms or mix up concepts), but I was thinking about “artificial gravity” in space. If a spaceship were being propelled by some force, a passenger would experience an acceleration. So ok, I’m pretty much ok with that situation. In a sci-fi rotating ring ... |
I simply don't understand the reason such collisions are elastic.
The elastic collision should be satisfying 1. (kinetic) energy conservation and 2. momentum conservation.
Lets saying the wall is on $x = L_{x}$, and the x-dir velocity of a molecule is $ v_{x} $.
The textbook and other sources that I saw, after the coll... |
This is a follow-up to this previous question. We are encouraged to use 4-vectors to solve these types of problems:
Decay kinematics using 4-vectors.
Here we look at the kinematics of particle decays and how 4-vectors can simplify this type of problem quite considerably. The point here is to use energy-momentum 4-vect... |
How does curved space explain why a denser object of the same shape and volume feels heavier?
|
Let me begin the question by admitting upfront that my knowledge of physics is limited only to high school and I am extremely rusty with that.
With the above out of the way, I want to understand the following better. So, it seems that the high school description of Newtonian mechanics leaves a lot to be desired (at lea... |
I am working in extensions of General Relativity Theory and at the moment of taking the Newtonian limit of this extension theory (essentialy, mathematically speaking, this is just linearizing the field equations obtained via the variational principle, but this is not important) I arrive to the following partial differe... |
I am a second year physics student. I am following my regular classes and additionally trying to improve my mathematical tools. I am wondering whether is there any course or textbook about the symmetry notion and insights of it?
|
I hope it's ok to post this question. I came across a random video on Youtube and this deer was hit by a car. Upon impact, however, his body flew up pretty high before hitting the ground. I was wondering why that's the case? I would imagine him being thrown in the opposite side of the car's velocity instead of up.
http... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.