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Electromagnetism can be modeled as a $U(1)$-principal bundle over Minkowski spacetime. The strength of the electromagnetic field is given by the 2-tensor $F_{\mu\nu}$. In differential geometry this is the curvature tensor, and so when $F_{\mu\nu}$ is nonzero there is some curvature present in the bundle. Is there any i... |
I am only a amateur solving the time-independent Schrödinger equation, and I only know how to solve the 1D box. When I went to search up more realistic examples, i.e. the Coulomb well, no one seemed to provide a solution with steps on how to derive it. Can someone, please provide an answer with detailed explanations?... |
I'm reading TASI Lectures on Inflation(https://arxiv.org/pdf/0907.5424.pdf). On page 20, it says
... also called the Friedmann Equations
$$\tag{21}
\boxed{H^2=\left(\frac{\dot{a}}{a}\right)^2=\frac13\rho-\frac{k}{a^2}}
$$
...
... Eqn.(24) may be integrated to give
$$\tag{26}
\rho\propto a^{-3(1+w)}
$$
Together with t... |
Relativity tells us that there is no preferred reference frame, yet current cosmology does operate on the hypothesis that all points in the observable universe originate from the same big bang instanton. So in principle there is a common point to measure time from throughout the universe. It seems at a minimum every ... |
with distributing magnetic bipolars in vacuum, we have the magnetization:
$$\vec{M}= \frac{a}{\rho}M_{0}\hat{\phi}$$
in the region $0<a\leq\rho\leq b$ , $0\leq \phi<2\times\pi$ , $0\leq z\leq h$ in cylindrical coordinates.
$M_{0}$ is a constant with the unit $[\frac{A}{m}]$. there is no magnetic bipolars in other pl... |
Is the following statement true?
If $\frac{\partial \dot{q}}{\partial q}=0$, then the conjugate momentum $p_q$ is conserved.
We know that conjugate momentum of $q$ is conserved if $\frac{\partial L}{\partial q} = 0$.
If $\frac{\partial \dot{q}}{\partial q}=0$, applying chain rule implies
$$ \frac{\partial L}{\partial q... |
On page 14 of Peskin&Schroeder, the authors are calculating the amplitute of a free particle propagating between states $|\vec{x_0}\rangle$ and $|\vec{x}\rangle$ using relativistic quantum mechanics of a particle.
The integral of interest reads:
$$\langle\vec{x}|e^{-i\sqrt{\vec{p}^2+m^2}}|\vec{x}_0\rangle=\int\frac{d^3... |
In the beginning of every physics class in school, we learn vectors.
And, then learn their algebra.
Then start using them, as we do with a lot other math branches, in physics.
We say that the force is a vector because:
It is dependent on displacement, and derived from it, multiplying scalars and scalars; and by laws of... |
This is a diagram for the input signal through a logic gate circuit, but im not sure whether the points where jt goes up/down signify a 0 or 1.
|
Torsion tensor $T$ associated with an affine connection $\nabla$ on a smooth manifold is defined as a (0,2) tensor field as follows:
$$T(X,Y) := \nabla_XY-\nabla_YX-[X,Y]$$
I understand that this is set to zero by the choice of the Levi-Civita connection, but I've read that the following condition (now stated in abstra... |
Whenever we calculate any lengths in Physics, we tend to express using displacements. For example, while calculating energy, which is given by the formula-
E = Fswhere E represents the energy, F represents force applied and s represents displacement.
Why do we use the shortest distance to calculate, shouldn't the tota... |
I am currently coding a 3D (Monte-Carlo) implementation of the Ising model, using the single spin-flip & Wolff algorithm.
So far, I was able to calculate all the interesting observables, like $M$ and $\chi$.
Now I want to implement the two-point-correlation function, but I am struggling here both in understanding the f... |
How can the temperature of a body change unless heat flows in or out of it?
So shouldn't all adiabatic process be considered isothermal too? but that is not true as both the processes have different equations.
|
Is the electric potential at the mid point between two equally oppositely charged plates zero.
granted between the plates there is uniform fields.
and what would the resultant potential graph look like due to the two plates. That is between the two plates only.
|
I'm covering the Hydrogen atom wavefunctions $\psi(r,\theta,\phi)$ which are separated into three functions $R(r), \Theta(\theta), \Phi(\phi)$. ((The function $Y(\theta,\phi)$ is what we call a spherical harmonic)). $\theta$ runs from $0$ to $\pi$ and $\phi$ runs from $0$ to $2\pi.$
We require $\psi$ to be normalizable... |
If we have a challenge to increase the mass flow rate in a CD nozzle, with additional condition like no structural changes are allowed, and cooling the nozzle is not allowed (inefficient), and you cannot change the medium of flow (to change density or other parameter).
How can we increase the mass flow rate in such a c... |
Earth moves in a few different ways through the universe. Earth orbits the Sun (plus the orbit precesses), the Sun moves through the Milky Way, and the Milky Way moves through the universe.
Compared to my position exactly one Earth revolution around the sun, approximately how far have I actually moved relative to my st... |
Let's consider a real source emitting a sequence of single-photons (like for example a N-V colour centre pumped with a pulsed laser with highly accurate frequency of the pulses). I want to characterize the source. In particular I want to directly verify experimentally that in each of the sequential time slots at most 1... |
I lately have been confused by the work energy theorem which states that:
Work done by all the forces on an object is equal to the change in kinetic energy.
However, I have a doubt
Consider we have an object resting on the ground. We lift the object from the group and bring it to a height say $h$. We ensure that the ... |
I am asking within the context of electromagnetic theory. Much of the discourse I could find in the literature was more focused on the phase differences between the scattered fields of various particles, rather than the phase difference between the incident and scattered field.
For the case of a single Rayleigh scatter... |
I more or less understand the complications and difficulties in combining the two theories, but what confuses me is why physicists have assumed that this combination makes sense in the first place.
It is not obvious to me, given the evidence that we have, that the two theories can be combined at all. It seems that the ... |
Consider a simple $LC$ circuit in which the charge on the capacitor varies sinusoidally. Current flows in this circuit, changing the charge on the capacitor and hence changing the electric field inside the capacitor. Shouldn’t this time varying electric field produce a magnetic field in the capacitor and similarly an e... |
The Hamiltonians corresponding to beamsplitter and squeezing operators are respectively:
\begin{align}
H &= ab^\dagger + a^\dagger b \: (\text{beamsplitter}) \qquad H = a^\dagger b^\dagger + a b \: (\text{squeezer})
\end{align}
Usually when considering the evolution of the modes $a, b$ undergoing respective beamsplitte... |
Suppose we have a uniformly charged hollow cone(ice cup) of surface charge density σ, slant height L and the half-angle at the vertex is θ. I want to calculate the electric field at its tip using Gauss law. I have done the calculation using Coulomb's Law by dividing the cone into rings of thickness dx and integrating o... |
Computing the entropy of a single particle has a number of pitfalls, however there seems to be a classical definition that should work.
This answer provides a definition of temperature for $N$ classical particles by using a probability distribution $D$ on phase space, setting up the maximization problem using Lagrange ... |
I'm a bit confused on how to approach a minimization/uncertainty problem. Say we have some function:
$ a(b) = \int_{0}^{b} \frac{dx}{1 + C \cdot g(x)} $
And we have experimentally determined $ a_{\mathrm{measured}} $ and know what $ b $ should be theoretically, and know their uncertainties ($ \sigma_{a_{m}} $ and $ \si... |
Why is there no current in a magnet even though magnetic field is present?
We know current is produced due to magnetic field and vice versa. But there is no current produced in a magnet, why?
|
I am trying to find information about the absorption response of the cones in the eye to different wavelengths of light. I have noticed two types of graphs and answers: one which shows the S-absorption peaking at about 420 nm, and another which shows it peaking at about 440 nm. What is the difference between these two?... |
I'm not sure if this makes any sense, but could I calculate the kinetic coefficient of friction between sandpaper and sandpaper experimentally, then divide it by 2 for the coefficient of friction of sandpaper and a point mass? Or should I keep it as the kinetic friction between sandpaper and sandpaper?
|
There are several theories for the fractional quantum Hall effect. The last listed in the Wikipedia article are composite fermions, though these seem to be a subset of fractional exchange statistics:
A finite group of anyons has some character that defines their Cayley graph. But you can view $n$ vortices as a rose, wh... |
This might sound a very amateur question but I couldn't find the answer anywhere. Simply, what is the meaning of Gibbs average? I've came across this term on the paper: Transmission of Information between Complex Networks: 1/f-Resonance (https://arxiv.org/abs/1112.5553) (precisely, in the equation 3; saying that an ave... |
I understand that there is a basic energy to the vacuum, the observable universe and any matter beyond it is surrounded by and infinite continuous spacetime, does the energy of that spacetime exert any sort of gravitational pull on the matter in the universe, I know it doesn't account for the expansion of the universe ... |
So I know a bird can stand on a power line without being electrocuted because there is no current going to the ground. However, I know that curents will pass to different electric potentials. My question is, if a bird has only one foot on the wire instead of two, would this open the current and allow the energy to buil... |
Thanks for anyone that can help.
Say we have a rocket engine in the vacuum of space with exhaust velocity of 2,000m/s or more, but low pressure exiting nozzle, say 1-2psi. A wider nozzle engineered for space, with low exhaust pressure. The rocket is landing on an asteroid, a crater, a moon, whatever. Something with no ... |
In physics, the fundamental description of physical theories frequently revolves around the concept of a Lagrangian. My expertise encompasses diverse algebraic formulations within the domain of Quantum Field Theory (QFT). For instance, considerations extend to formulations pertinent to the free scalar field, chiral bos... |
I have been researching electro lasers. However I keep on finding resources of pulsed electro lasers however I have not found any resources on continuous wave electro lasers. So could continuous wave lasers exist wave lasers and if so what would their wattage be? From a human being.
|
In any book that I studied, never saw anything like "position of a wave". Does it have to do anything with quantum particles showing so called "superposition".
|
Say we have a rigid tank of nitrogen gas ($N_0$ molecules) at temperature $T$. The tank is in vacuum. If we now punch a small hole on the tank, the gas will leak. Assume the hole is small enough so the gas inside is remains ideal. The tank is not fixed so it is accelerated by the leak. What is the average energy of esc... |
I'm studying about the exchange interaction and it's quite confusing.
Why does it happens between same kinds of particle?
How about electron and muon? Or one particle and another one which has all the same properties except mass?
|
I read that Beats are heard when sound waves with same amplitude and a small difference in frequency are travelling along the same direction are superimposed, but in problems related to frequency, the sources of the two sound waves that are superimposed are not the same,hence, when they superimpose at a point, and we a... |
Although title is more broad, and you are welcome to give examples, I will ask about why we accept certain things as acceptable in Einstein's thought experiments using a specific experiment:
Consider the famous mirror in a train example:
There is a train moving with velocity $v$ relative to earth. The train has height... |
I'm confused about the term wave group velocity: It is usually explained in terms of a superposition of harmonic waves with very closely spaced wave vectors and frequencies. It is then easily shown, that the envelope of such packet moves with group velocity
$$v_g=\frac{d \omega(k)}{dk}$$
On the other hand, the individu... |
I read that when two waves are superimposed we can find the resultant wave by adding the equations of the two waves. Now, I also learned that when two waves travelling along "same direction" and with "same frequency" are superimposed,the net amplitude of the resulting wave can be found by the treating the amplitudes of... |
I'd like to simulate sun effects on a material affected by UV and IR.
Actually is winter and I'll need to wait 6 months to have maximum sun intensity and be able to expose it to direct sun.
I've a halogen lamp of 220W, working at 220V, that is inside a parabolic reflector. Whitout protection glass I've a very similar e... |
Why, when determining the lengths of pendulums for a pendulum wave, do you use the equation $L = g[Tmax/2π(k+n+1)]^2$?
|
Error of measurement is defined as the result of a measurement minus a true value of the measurand (Source: Page no. 36)
Uncertainty (of measurement) is a parameter, associated with the result of a measurement, characterizes the dispersion of the values that could reasonably be attributed to the measurand. (Source: ... |
I am studying Exact RG and I have a question.
I think, it should be possible to reproduce the flow equation of $\lambda_4$ term in perturbative RG, from exact RG.
However, from Peskin, equation of $\lambda_4$ is like
\begin{equation}
\frac{d\lambda_4}{dt} \sim \lambda_4^2
\end{equation}
when I use $t=\log \Lambda$, whe... |
I am trying to understand how to calculate the necessary force to start moving a train and I was wondering about the roles of rolling and static friction into the equation. From several sources I read that the rolling friction coefficient is about 0.0015 and the static friction ranges between 0.35 and 0.50 for most tra... |
In the double slit experiment, a source of particles is pointed towards a wall with two thin slits, the state of the particle before a dot appears on the screen is represented by a linear superposition of all locations. I have two questions:
What is the probability that a dot will appear on the screen in a time $t$ af... |
While reading some papers on Einstein's theory of relativity, seeing how the flow of time is not the same for everyone, a doubt occurred to me:
Let us imagine a photon moving in a well-defined space at the speed of light. While it will not "feel" the passage of time, according to our point of view the photon will come ... |
We have a system of point charges in free space ,due to which electric field has some value at each point . Now we introduce a dielectric material into this configuration at some location where no point charge is present . Would the presence of this dielectric change the value of electric field at any point outside i... |
The representation of any operator $F$ in the fermionic Fock space in terms of displacement operators as -
\begin{equation}
F = \int d^2{\bf{\xi}}~f(\xi) D(-\xi)
\end{equation}
where $f(\xi)$ is the weight function and $D(\alpha)$ is the displacement operator and $\xi$ be the Grassmann variable.
For any set $\alpha=\{\... |
We say that a geodesic is (future ) inextendible if there exist no (future) endpoint for example. Wouldnt that imply the domain of the geodesic is $[p, \infty)$ with some beginning point $p$? And it is incomplete if there is a gedesic with finite affine length, i.e. there exist inextendible geodesics (at least in one d... |
The general equation of an oscillator with a damping term $-rv$, where $r$ is damping coeffeciet and $v$ is velocity is
$$x=e^{-pt}(Ae^{qt}+Be^{-qt})$$
where $p=r/2m$ and $q=\sqrt{p^2-s/m}$, $s$ is Hooke's constant, $m$ is mass and $t$ is time
Now I don't understand why we physically cannot have $q=0$. Almost every aut... |
These are a few basic questions of mine in thermodynamics whose answer I can't find anywhere.
$1$. How does a quasi static process serve the purpose of thermodynamic equilibrium?A quasi static process is one which occurs slowly enough so that the gas is in thermodynamic equilibrium at every instant which means i have i... |
An electron is usually defined to have a charge of 1.602 × 10-19 coulombs. But a Coulomb is the amount of electrons accumulated in 1 second = 6.24 x 10^18 charge carriers. An electron charge is defined in terms of a percentage of the number of electrons accumulated in 1 second?
Isn't it a bit useless to define it as su... |
Suppose an interface with the wave function of left side a plane wave $A e^{ik_1x}$, and the right side a helical wave $Be^{ik_2x}e^{im\theta}$, $m \ne 0$ is the orbital angular momentum and $\theta$ the azimuthal angle. Can this setup meet the wave function continuity?
|
The intended output of many lasers in laser scanning is Gaussian. At distance $z$ from the waist, the radius of a Gaussian beam is calculated as
$$w(z) = w_0 \sqrt{1+(z/z_R)^2},$$
where $w_0$ is the waist radius, and $z_R = \pi w_0^2/\lambda$ is the Rayleigh range, depending on the waist $w_0$ and the wavelength $\lamb... |
Consider an expansion channel, where isothermal incompressible flow enters the domain from the smaller channel.
Assume I inject infinitesimal particles (with same density as the flow) into the domain from the red area, and let them move with the streamlines. I think the scalar quantity representing the volume fraction ... |
If you had a loop made of completely transparent glass (or other material), in the shape of a donut; think atomic collider (but probably not needing to be so large :) ), and you introduced light from a "port" on the edge (that wouldn't allow light to escape if the photons are travelling in one direction), such as from ... |
In Julian Schwinger's book Quantum Mechanics: Symbolism of Atomic Measurements, pg.33, he says that the process where nothing is measured (represented by the unity symbol $1$) is equal to the process where a physical variable $A$ is measured and every possible result is accepted. This is called the completeness relatio... |
There apparently was recent experimental validation of a protocol (ref 1) which allows an exchange of energy between 2 individuals who have entangled spin chains and one user passes a classical key to the other user. While this is characterized as pulling energy from the vacuum, it does open up teleportation options t... |
Here is the contradiction, which I arrive at.
Renormalization group (RG) eqs. are basically a statement that observables (cross-section or Green's function) don't depend on the arbitrary renormalization energy scale $\mu$ (in the context of $\overline{MS}$ scheme dim. reg.).
Asymptotic freedom was observed and awarde... |
I have a question regarding what I think should be a simple dynamics problem, but somehow I’m struggling with it.
Imagine an object with mass $m$ coming from the left with velocity $v$. An identical object is hanging on a massless rope. I chose a frame of reference in which the axis around which the second object can ... |
My question is regarding what happens with $\vec D$ and $\vec H$, when the medium changes, in the case of $\vec D$ when the dielectric changes from $\epsilon_1$ to $\epsilon_0$ or to another $\epsilon_2$ and in the case of $\vec H$ when we change from a paramagnetic material with $\mu_1$ to $\mu_0$ or other $\mu_2$. I ... |
Suppose you have two superconductors that resemble rectangular prisms with identical width and length. The first superconductor call it $A$ is shorter than $B$ visualized below:
Now both $A$ and $B$ are somehow carefully cooled and pinned over an identical magnet from an identical height so that they have flux tubes ... |
in the first part (i) i am not able to understand why these resistors are considered that they are parallel. is because of the joints?
|
The following generalization of angular momentum is given on page 571 of the third edition of Goldstein's Classical Mechanics:$$\mathcal M^{ij}=-(x^iT^{j0}-x^jT^{i0}).\tag{13.44}$$The metric used in this case is the Lorentzian one with signature $(+,-,-,-)$.
Since the ordinary relativistic generalization is given by, $... |
Please be kind - have probably a silly question about static electricit, the type when you walk across a carpet and touch something and you get a spark/shock on your finger.
Hoping someone here can answer as I’m getting confused.
If I’m holding say a cell phone in a rubber case and I have built up static charge on me, ... |
If I have a rigid rod and I apply a force $\vec F$ distance $r$ away from the centre of mass the torque on the rod is $\vec r \times \vec F$ from the centre of mass and the torque causes the rod to have a proportional angular acceleration.
So could the laws
$$\vec \tau = \vec r \times \vec F, \quad \vec \tau = I \vec \... |
I always thought that object turning means acceleration but what if an electron is caught inside a magnetic field that simply changes it path into a circular one so no electric field is allowed. The electron would be doing circle at the same speed so it seems contradictory, how can I resolve this problem?
|
In various references, we see the construction of unit cells of carbon nanotubes from chiral and translational vectors.
The chiral vector is given as:
$$\vec C_h = n\vec a_1 + m\vec a_2$$
While the translational vector is given by:
$$\vec T = t_1\vec a_1 + t_2\vec a_2$$
Clearly, $\vec C_h$ and $\vec T$ must be orthogo... |
I am looking to irradiate water containing some amounts of iron and would like to measure the amount of hydroperoxyl and hydroxyl radicals produced in real time as a result of the irradiation. Is there any way to do so without very expensive equipment such as an EPR machine?
|
I kept a ceramic cylinder wrapped in a Moly sheet. This whole thing was kept on an another Moly sheet inside muffle furnace. I ramped up the muffle furnace to 800°C in half an hour, kept there for half and hour and reduced it to room temperature in half an hour. I opened furnace at 352°C and saw that Moly has completel... |
Imagine a planet with the same properties as Earth, this time moving in an elliptical orbit around a black hole of a large number of solar masses. Also imagine that the surface of this planet is as massive as that of the Earth and that you can therefore experience a normal force on it as on the Earth's surface. At a sp... |
If the energy of a photon increases under the influence of time dilation in a gravitational field, does this have an effect on the photoelectric effect? Does this mean that the photoelectric effect in a specific experiment could take place at the gravitational field of the Earth's surface but not at high altitudes wher... |
The (failed) goal of the Michelson-Morley experiment was to detect the motion of the Earth with respect to the hypothetical ether. As far as I understand (e.g. from the exposition in Feynman’s textbook, Ch. 15.3, and some other textbooks) the only property of ether which was used is that the constant $c$ from the Maxwe... |
How to find tachyonic instabilities for some parameter ranges in the $f(R)$ gravity model? I have tried to find the parameter ranges for exponential $f(R)$ model, Starobinsky $f(R)$ model and Tsujikawa $f(R)$ gravity model, but could not find any proper ranges which lead to tachyonic instabilities
.
|
I need to prove that the energy-momentum tensor density is defined as:
\begin{equation}
\mathcal{T}_{\mu\nu}=-\frac{\partial \phi}{\partial x_\nu}\frac{\partial\mathcal{L}}{\partial(\frac{\partial \phi}{\partial x\mu})}+\mathcal{L}\delta_{\mu\nu}
\end{equation}
satisfies the equation $\frac{\partial \mathcal{T}_{\mu\nu... |
In my notes of topological QFT we demonstrated that the holonomy associated with a path in $\mathbb{R}^3$ is invariant under smooth deformation of the path if the connection is flat.
Then I wrote:
If we do a smooth deformation of the path shrinking it to a point, since the holonomy $H_{\gamma}$ is invariant it corresp... |
The equation of motion for a damped harmonic oscillator is
$$m \ddot{x}=-sx-r\dot{x}$$
where $s$ is Hooke's constant and $r$ is damping coefficient.
For Damped Harmonic motion,
$$x=Ae^{-pt}(\sin(wt+l))$$
Where $A,l$ are constants of integration, $p=r/2m$ and $w=\sqrt{s/m - p^2}$
The energy/work is defined as the line i... |
Why do many science communicators say that negative masses fall upwards? Is it the same in the physics literature that they say that negative masses fall upwards?
In general relativity, things don't fall down, it's the earth that accelerates upwards.This is from the Einstein Equivalence Principle. It states that standi... |
I will go straight into an example. Let's take the case of an electron of mass $m$ confined in an infinite 1D box of width $a$. Solving the Schrödinger equation and pay attention to the boundary conditions will give us the set of wave-functions:
$$\psi(x) = \sqrt{\frac{2}{a}}\sin\left( \frac{n\pi}{a} x \right),$$
where... |
While an individual photon has no rest frame, when two photons move apart, it makes sense to ask where their centre of mass is, as described here.
If I proposed that while a photon has no mass, a system of two parting photons does have mass, how would I quantify that mass, in a manner consistent with the prevailing the... |
If current has two ways to flow in a single circuit, let’s say one path has a resistor of 5 Ohms and the other has no resistors whatsoever, will current still flow in both of the conductors?
Can anyone help me with this question since the answer for the reading of ammeter is 4.5A but the solution implies that the curre... |
More generally, my question is about the similarity between an $N$-slit and an $N$-mode beam splitter. Conceptually speaking, would it be accurate to say that the beam splitter is just the discretized version of the slit? (Let's simplify things and ignore the specific parameters of each such as slit width, transmittanc... |
Considering other mean field approximation (e.g. Max entropy approach or $<S_i> = m_i
+\delta S_i$ , $\delta S_i \simeq0$), a common approach that I've seen is that of maximising the partition function $Z$ of the Boltzmann Distribution $\frac{1}{Z}e^{-\beta E(S)}$.
Going into the Weiss Mean Field Approximation, startin... |
I am trying to draw out electric field lines for different conducting bodies, and I know that electric lines in case metallic conductors incident and emerge out perpendicularly, considering a parallel plate capacitor's base component is a metallic conducting plate(s), the electric fields should be perpendicular through... |
Let's consider an $\rm NH_3$ molecule.
The Hamiltonian in the $\{|\psi_L>,|\psi_R>\}$ basis can be written as:
$$\hat{H}=\begin{pmatrix}
E_0 & -A \\
-A & E_0
\end{pmatrix}$$
Now by diagonalizing this operator we can find the following eigenvalues:
$$E_S=E_0-A$$
$$E_A=E_0+A$$
And their respective eigenkets:
$$|S>= \fra... |
Ok so I may be very much completely wrong about this, but as far as I understood from Veritasium's video, even though electrons themselves don't travel at that speed, information in the electrical field travels at light speed. So my question is, even though electrons in computer chips don't travel at light speed, infor... |
Pressure is defined as force per unit area. What is the meaning of unit and why is the term unit used with area?
|
I am looking into Weinberg "Quantum Theory of Fields" Volume 1 Ch. 12-1.
There, he discusses the general rules of power counting.
He defines the UV asymptotics of the propagator $\Delta_f$ for a field labeld by "f" as
\begin{equation}
\Delta_f(k) \simeq k^{-2+2s_f} \text{ as } k \to \infty.
\end{equation}
so that $s_f ... |
According to the output voltage equation, the output of a piezoelectric material increases when its dielectric constant is increased. But it reduces the coupling constant. Since that can we directly say the behavior of piezoelectricity with respect to the dielectric constant?
|
I am reading H.B. Callen - Thermodynamics, and I am having a hard time understanding a lot of its logic. One example is in the first chapter (chapter 1, sections 5, 7, 8), where he talks about measurability of internal energy.
He starts saying that the state of a system (in simplified conditions, such as no charge, no ... |
What are some good, possibly modern, references for Hanany-Witten brane setups? I know the one of Giveon and Kutasov: Brane Dynamics and Gauge Theories, but I would like to have some more since this one is not super clear to me, beside being a quite old reference. Moreover I would like something that goes straight to t... |
I've noticed what seems to be a fine-tuning issue. To be more specific, electric neutrality implies that the amount of lepton asymmetry produced through some unknown processes precisely cancels out the baryon asymmetry produced by some unknown processes. This precise cancellation appears to me as a fine-tuning issue. P... |
The so-called freeze-out of dark matter is based on a homogeneous description. However, in the later stages of the universe, where structures form, it seems very likely that the reaction rate would increase enough for dark matter and anti-dark matter to annihilate again in denser areas. If this is true, I believe the f... |
What gives us the certainty that the unit charge of a free electron - measured and confirmed with the highest precision in numerous experiments - is retained even when approaching and integrating into an atom and associated with the emission of EM radiation?
Subordinate questions, which should primarily serve to unders... |
Studying quantum mechanics, or QFT, the concept of generator $G$ of an infinitesimal transformation $T$ keeps showing up. My problem is that I don't have in mind a solid (dare I say "rigorous") definition for it.
Sometimes I have seen it defined as this:
$$T=\mathbb{I}+G\varepsilon$$
sometimes instead like this:
$$T=\m... |
I was reading a paper by Ed Witten called "Algebras, Regions and Observers". It can be found here: https://arxiv.org/abs/2303.02837
A major theme is theorems relating the algebra of observables for a spacetime region to a larger one. In section 3.3, it is claimed that the best one could hope for is the additive algebra... |
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