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This I feel is a bit of a complicated question, so I’ll quickly try to paint as clear a picture as I possibly can:
The magnet is spinning on an axis perpendicular to its poloidal axis (the line which can be drawn pole-to-pole) at the center of a coil of enameled copper wire which has a length parallel to the magnet’s s... |
I'm reading Nielsen and Chuang's famous book on Quantum Computation and Information. In section 2.2 on the postulates of quantum mechanics, they talk about quantum measurements starting with
Postulate 3
Quantum measurements are described by a collection $\left \{ M_{m} \right \}$ of
measurement operators. These are op... |
In quantum mechanics, time reversal takes the form of an anti-unitary operator such that we preserve the canonical commutation relations. We can assign relations for each of the measurables like p and x etc.
However, how does time reversal work when we have a Hamiltonian like
$H(t)=H_0 + V(t)?$
The first part is symmet... |
so I am quite confused regarding the spatial metric tensor $g_{ij}$. If I have $g_{ij}g^{ij}$ I essentially get the trace of the metric tensor $g$ right? Or, do I get $\delta^i_i = 3$ instead?
The second part to this is, does curvature matter? In a Minkowski metric, I understand that I'll get $3$ either way, but what i... |
According to Wikipedia, the conservation of momentum states that In a closed system (one that does not exchange any matter with its surroundings and is not acted on by external forces) the total momentum remains constant.
But according to Taylor, the conservation of momentum states that if there are no external forces ... |
I want to know how a material's resistivity changes after the dielectric breakdown voltage is applied and crossed. Let's say for a circuit after air becomes a conductor for E=30kv/mm what would be the current flowing in that circuit and how to find it?
|
In several different contexts, I've heard the claim that quantum gravity in an accelerating universe messes with our ability to define precise quantum observables.* One version of the argument goes roughly as follows; we need to perform a measurement infinitely many times to get a precise outcome. To prevent quantum fl... |
I am considering background events like, $p p \rightarrow t \bar{t}$ and QCD events where t is a top quark. I want also to reduced the QCD events such that QCD events will be less observed than that of
$p p \rightarrow t \bar{t}$. Is it okay technically, to apply different sets of cuts to different background process? ... |
Let say we have the state $ |\varphi⟩ = \alpha|0⟩ + \beta|1⟩ $
Measuring this state provoke a change, $\epsilon$ to the system, $S$, making the state of $|\varphi⟩$ collapse to either $|0⟩$ or $|1⟩$.
The laws of physics, as far as I know, are always stated as being reversible, meaning that no information is lost.
From ... |
I am studying string theory from the book "String theory and M-theory", written by Becker, Becker and Schwartz. My question is:
We are told that the Nambu-Goto action is simply the one that extremizes the area of the world-sheet. The area of the world-sheet is described by the induced metric
$$G_{\alpha\beta}=g_{\mu\nu... |
I have some read answers on this forum, some books like Halliday Resnick and my course books. I have understood that binding energy is the energy we need to supply to break nucleus into individual nucleons (or the opposite). What I can not understand is why a high binding energy or more released energy helps in stabili... |
Let's take an object (all times mentioned in this problem are proper times). There is a constant proper acceleration
"$a$" on this object in the x-direction for time $t, 0\leq t \leq \tau$. After this, there is the same proper acceleration in the y-direction for time t, $\tau \leq t \leq 2\tau$. What is the velocity o... |
How dose a Tidally locked gas giant have a balanced gravitational force to keep it's spherical shape when one side is constantly facing the sun? Where does it's gravitational force come from to maintain its constant somewhat spherical shape?
|
I am studying string theory from the book "String theory and M-theory", written by Becker, Becker and Schwartz. My question is:
We are taught that one of the advantages of introducing a field $e(\tau)$ into the action of the point particle, namely
$$ S_0=-m\int d\tau\sqrt{-\frac{dX^{\mu}}{d\tau}\frac{dX_{\mu}}{d\tau}}
... |
The equations for 1D compressible flow are
$$\frac{\partial u(x,t)}{\partial t}-A\frac{\partial v(x,t)}{\partial x}=0,$$
$$\frac{\partial v(x,t)}{\partial t}-B\frac{\partial u(x,t)}{\partial x}=0,$$
with $u(x,t)$ the velocity, $v(x,t)$ the specific volume and $A,B$ constant. A simple explicit finite difference formulat... |
Let’s say we want to do a Fourier Transformation (FT) of a function $f(t-t‘,r-r‘)$ i.e. the function to be Fourier transformed only depends on relative coordinates. This is for example the case if we have a translational invariant space and time.
My question is:
If we do the FT we will get two delta functions like $\de... |
I've been doing some research on the topic of radiation reaction force/self force in classical electrodynamics and although there are some discussions on the internet I would like direct answers to these following questions:
Is there a rigorous and universally accepted treatment of radiation reaction force in classica... |
There are two spherical conductor A and B,and their radius are $r_a$ and $r_b $, and their charge are $q_1$ and $q_2$, and $q_1+q_2=Q$.
Now they are connected with each other with a wire, assume the distance $d$ between them is longer than $r_a$ and $r_b$, so their charge is Uniform distribution, the figure is as b... |
Let's consider we have three arbitrary vectors A, B and C. We have the quantity $A_{\mu}B_{\nu}C_{\rho}$. Is it possible to break the above quantity into sum of symmetric and anti-symmetric vectors in any two indices?
|
I am interested in the stress tensor of a CFT_2 living on a conformally flat background, say,
\begin{equation}
ds^2 = \frac{1}{x^2}(-dt^2 + dx^2).
\end{equation}
What if I want to know the stress tensor in the (tt) and (xx) components? I can find endless resources on the properties of the stress tensor in 2d. But I am ... |
so I'm trying to derive an equation for the maximum height an object reaches after being vertically thrown upwards, where the two forces acting on it are gravity and quadratic air resistance, so that
$$
ma=-mg-kv^2.
$$
I'm trying to "fill in the gaps" of the derivation from this text, p. 2 under "Alternative Method".
I... |
My question is pretty much all in the title. I was always told that our planet is flattened at its poles due to the centrifugal force generated by its own rotation. However I don’t see how centrifugal force can explain anything at all, it not being a real force, but rather a mathematical expedient (together with Coriol... |
I'm wondering if one can say that a black hole is an object "made of matter" that has a size (as a size, I'm not talking about the size of the event horizon).
I would like to know if one can represent a black hole in the following manner:
If yes, what is the (typical) size of the black hole as an object?
PS: I'm not a... |
A black hole has a radius of $R = \frac {2Gm}{c^2}$, in this context, if we take a single proton and neutron as a black hole, its Schwarzschild radius will be near about $4.8 \times 10^{-52} \mathrm{m}$.
Now quantum mechanics says that both particles can stay together if they satisfy the uncertainty relation as $$\Del... |
In the standard classical Maxwell theory, we use the following arguments to claim that there are only two propagating degrees of freedom
$A_\mu$ has 4 components
$A_0$ is non-dynamical (-1)
$\mathcal{L}_\text{Maxwell}$ enjoys gauge symmetry and should be removed (-1)
So in total, we have $4 - 1 - 1 = 2$ dofs.
How... |
Since the weak interaction violates CP symmetry but electromagnetism doesnt,does it mean that the electroweak fields also violates CP symmetry?Can a field which violates some symmetry be the product of a field at lower energies which doesnt violate the same symmetry?
|
I've learned some basic ideas of group theory like the basis for a group representation.
In 2 spin-1/2 electrons coupling case,
it is said $$2\otimes2=1\oplus3.$$
The direct product can be reduced to some direct sum. The basis belongs to one representation of a "group".
My question is, what is the concrete "group" here... |
I'm trying to understand a phenomenon covered in several resources that I think I'm struggling with due to my lack of understanding of its meaning.
The idea is that 2 spin 1/2 particles can combine to form 4 spin states. These are broken down into the following prescriptions:
$$|1,1\rangle = |\frac{1}{2},\frac{1}{2}\r... |
EDIT: this question is ill posed because it describes an equation that adds two values that I claimed have different physical dimensions, which is incorrect. But I left the question up in case someone makes a similar mistake and ends up here.
I am trying to understand how to track the "units" (or dimensions) of the fol... |
Goal:
I am interested creating a simple gravity simulation and was wondering if it was possible to describe two objects motions through time with percision. All other parameters are known (acceleration, velocity, position, mass, etc.).
Current Approach:
I have a 2d plane and every 1/60 seconds the position, velocity, ... |
A 100 g ball with a speed of 5 m/s hits a wall at an angle of 45 degrees. The ball then bounces off the wall at a speed of 5m/s at an angle of 45 degrees. What is the change in the momentum of the ball?
When I look at this problem it seems intuitive to me that the answer should be 0, as the ball's mass remains const... |
This might sound a bit weird, but I do not understand what I am missing!
We have the combined gas law:
$$PV/T$$
And the ideal gas law:
$$PV/nT$$
My first question is that why didn't French physicist Benoît Paul Émile Clapeyron consider the number of moles in his equation?
It is because Avogadro's law: $v/n= v/n$ wasn't... |
My teacher said that in equilibrium no matter what approach we use we arrive to same result i.e. in this case ideal gas equation. So if we were to use the two approaches (thermodynamics and kinetic theory respectively) will the two approaches lead to different results
|
I am doing some research on asymmetric magnetic fields. I have simplified my problem to an isosceles triangle mangnetized with the N side on the tip with the smallest angle and the S side opposite of it. I am attempting to determine where the boundary from N to S will be and the curvature (if any) of that line.
I am h... |
The ODE for a driven harmonic oscillator is given by
$$
\ddot{x}+2\gamma \dot{x}+\omega_0^2 x = \frac{F}{m}\cos(\omega_dt)
$$
By assuming balance of forces, i.e. energy conservation, one can solve for x and eventually arrive at
$$
\sigma=\arctan \left(\frac{\gamma \omega_d}{\omega_0^2-\omega_d^2}\right)
$$
which descri... |
When two neutron stars collide they may form a black hole which is not a supermassive black hole but it should provoke that outside its newly formed event horizon photons are emitted as a consequence of the titanic collision and this EM-radiation is highly redshifted but also slowed down by black hole gravitational tim... |
While solving for the chemical potential of a fermi gas at $T\ne 0$, we first take
$$n = \int_0^{\mu}g(\epsilon)d\epsilon+(\pi^2/6)(k_BT^2)g'(\mu)+O(T^4)$$
Which is obtained by the Sommerfeld expansion. After this step, the author has stated the approximation,
$$\int_0^{\mu}H(\epsilon)d\epsilon = \int_0^{\epsilon_F}H(\... |
I have read at different places that in 3 spacetime dimensions, there are NO propagating gravitational degrees of freedom. This seems to imply that we have only "non-propagating" degrees of freedom. What does that mean?
For concreteness, let me give two examples where I encountered this such statements:
In Supergravit... |
I have just taken apart a broken USB microscope, and recognized that there is actually no magic going on inside.
So I thought how about building one of my own. The idea is to buy a regular (possibly used) optical microscope's objective lens and a USB webcam. All still low to mid cost, of course. I think I have learned ... |
When calculating for Torque in torsion or for Moment in the case of bending, the concept is usually first introduced with the simplification of the assumption that the stresses and strains are in the elastic region of the material, appended by perfect elasto-plastic assumption of the material. And later for the same ca... |
So I am trying to do a question where I have two objects that are rolling without slipping. We have found the potential function for this setup, have found the H, we are given y and we're also give the Icm in the problem. The small semi circle has mass m.
I have had many approaches to this question and can't seem to f... |
Based on this question
Ampere's law and Biot-Savart law gives different terms for magnetic field in middle of a current running in a loop
I made the following square Amperian loop:
where I have colored the section of the line integral that would cancel each other, as well as side 4 that canceled itself.
This is bogu... |
I'm studying Alexander Friedmann's equation about the Hubble parameter and, thus, the time dependence of the cosmic scale factor varies as the matter density, ρ, and as the dark energy, Λ as shown in the picture:
|
In the PBS spacetime video about charge (https://www.youtube.com/watch?v=esayi49OAk4), at 10:55 he said that weak hypercharge is carried by the $Z$ boson. Is this accurate?
|
For visualization purposes, let’s say I slam my hand into sheet metal and it vibrates. Will that vibration extend beyond the metal sheet into the space surrounding it, and would that energy wave permeate into space forever? (even if it’s on a very small scale)
The question I’m trying to get at is: does an excitation of... |
Expanding on the title, I am hoping for a little bit of insight into the philosophy of Newton's mechanics as a physical theory. My question, essentially, is does a point mass have constant mass by definition?
Elementary textbooks (I am using Taylor's Classical Mechanics) introduce Newton's three laws in the context of ... |
It is my understanding that at low gravitational potentials like we experience on earth that the time curvature dominates and that the curvature of space only becomes relevant within stronger gravitational potentials.
I know GR has been validated to great precision around earth and the sun. Do these validations of GR ... |
I am taking physics. There was a problem which was talking to a person who can exert force to the book so that it won't slip down vertically. In the answer book it was saying, the two normal force is working on the $x$-direction. Could anyone clear me up about this normal force?
|
Say I have two Wigner functions $W_1(x,p)$ and $W_2(x,p)$ representing pure states on optical phase space, and I want to know what the Wigner function of their superposition $W_{1+2}(x,p)$ looks like (let's say an equal superposition for this case). Is there any way to combine the functions to find $W_{1+2}$ without de... |
How much thrust could a solar sail receive from sling shooting around the Sun and riding the wave of a solar flare during the escape?
I found this link https://ww4.fmovies.co/film/the-ark-season-1-1630854809/ at 23:32 somewhat examples the maneuver.
|
Consider a man with a thick padded punching glove who strikes a bag. He then strikes that same bag without a punching glove. Both punches travel at the same velocity. Which one exerts more force? Which one takes longer to stop?
Here's my understanding:
We know by newton's 2nd law that $F=ma$. With the glove there is mo... |
The dimension of the stress-energy-momentum tensor is similar to that of pressure, according to wikipedia.
The stress-energy-momentum tensor $T_{μν}$ is defined as $μ$ momentum in a spacetime box of volume $ν$. So, its dimension must be similar to that of momentum per unit volume.
Where am I wrong?
|
I'm a college student majoring in chemical engineering and I was simulating a pipe design using a versatile plant designing and chemical engineering tool, Aspen Plus.
The thing I wanted to ask a question about is, the simulation showed that when there is a pressure drop inside a horizontal pipe due to friction, the vel... |
This is a very trivial question I suppose.
But, I dont remember any other sources of light mentioned anywhere other than the atoms emitting radiation due to electrons changing energy levels.
So, are there any other sources? What are they?
(Edit- In other words Iam asking for other light/electromagnetic wave production ... |
In isothermal reversible process is pressure constant along with temperature if not then why change in enthalpy is zero as the formula $\Delta H = n C_{p} m \Delta T$ valid for constant pressure?
And if pressure is constant then why not $\Delta H = q = 0$?
|
I am reading Susskinds book General Relativity: The theoretical minimum and I got a bit stuck on the transformation rule of contravariant components. The book defines the components of a vector $(V^{’})^m=\frac{\partial Y^m}{\partial X^p}V^p$ where the primed system corresponds to changing from coordinates X to Y. My q... |
Why some books write light itself is invisible but makes things visible for us. I mean if a laser beam is passing just parallel to our eyes in a dust free environment we can't see it but the reason for this is that position of our eyes was such that no amount of light got a chance to enter our eyes. Even if a table is ... |
I was solving this question and ended up getting an incorrect result. So this is the answerkey provided .
So I noticed that the author explains work done by friction is converted completely to potential energy in the spring and the main reason behind this is because the question mentions "A force F drags slowly...".
W... |
What exactly is the motivation for the use of the Self-Dual Canonical Anticommutation Relation (CAR) algebra in the context of infinite lattice systems? Why not remain with the CAR algebra, as both are in some sense $^*$-isomorphic to one another.
|
I'm trying to understand power and torque relationship in terms of cars.
Let's assume we have a four tracks with a load that needs a total of 1000N to move.
First one has 1000 Nm and 1000W
Second one has 1000 Nm and 2000W -> (Q1) Is my understanding correct, that no.2 will move the load on the same distance 2x faster... |
When light enters water, the light changes their direction because they only use 75% of their speed in water, because the interactions with the electrons, the wavelength of the photon changes. We SEE the light change direction, but why can't we see the wavelength change too? Shouldn't wee see another color because the ... |
A circular coil carrying current has a magnetic moment associated with it and it produces magnetic field. A electron spin also has magnetic moment associated with it. Hence it should also produce magnetic field. (I seen papers where they measure Magnetic field created by a collection of spin). Can i just plug in electr... |
It must not be pressure because it is a energy.
|
I found this statement in a discussion about the application of local Lorentz symmetry in spacetime metrics:
Lorentz invariance holds locally in GR, but you're right that it no longer applies globally when gravity gets involved. While in SR, quantities maintain Lorentz (or Poincare) symmetry via Lorentz (or Poincare) ... |
Ballentine's textbook presents an experiment with entangled electrons (page 271 of the pdf, problem 9.6) whose resolution of the "paradox" can be found in the chapter "solutions" (pages 646-647 of the pdf):
https://faculty.washington.edu/seattle/physics441/online/Ballentine.pdf
The solution is:
The probability density ... |
For the sake of simplicity, assume a 3 level system, subject to a Hamiltonian $H_0$. The Hilbert space is then completely spanned by 3 states with energies $E_1$, $E_2$ and $E_3$.
I'd like to understand what happens in the following experiment:
I prepare the system in state $|1\rangle$
Now I illuminate the system with... |
White light can be produced by the mixing of red, green and blue light.
If one mixes red and green light, one gets yellow.
Why, then, does the mixing of yellow and blue light produce green, rather than white?
|
I'm trying to understand something from my Special Relativity notes.
Assume here that $\vec{E}$ and $\vec{B}$ are perpendicular and $|\vec{E}|>|\vec{B}|$.
Show that there is a frame $\bar{\Sigma}$ in which $\bar{\vec{B}}=0$.
This I understand, if we imagine having a boost in the normal direction to both $\vec{E}$ and... |
What i mean to ask is that, i learnt that EM waves are just disturbance in the already ever existing EM field, so when there is a charge in space, does it enhance the field in its required direction or it creates new ones, i had a perception that EM field exists every where with no or very little magnitude and the em w... |
Suppose that I have a metric $g_{ij}$ with covariant derivative $\nabla_{j}$ and another metric, $\gamma_{ij}$, with covariant derivative $D_{j}$ that is conformally related to $g_{ij}$ as $\gamma_{ij} = \psi^{-4}g_{ij}$.
I am confused how $\nabla^j K$ and $D^j K$, with $K$ a scalar, are related. Evidently, I think tha... |
I am working on a specific example where the metric I am using is the $AdS_4$ metric whose ricci scalar $R=-12/l^2$ for some characteristic scale $l$: $$ds^2=-\cosh^2\left(\frac{\rho}{l}\right)dt^2+d\rho^2+l^2\sinh^2\left(\frac{\rho}{l}\right)(d\theta^2+\sin^2\theta~d\phi^2)$$
And more specifically, I am looking at a p... |
Does heat is sum of all All types of kinetic energies of all the molecules or just the translational k.E of molecules???
|
I'm studying from "Solid State Physics" by Ashcroft-Mermin. In particular, in chapter 12 it talks about the semiclassical model and tries to reason about the Hall effect in the limiting case of high magnetic field.
The first case the book considers is when, in a band, either all occupied or all unoccupied levels give r... |
When Dirac derived his equation he started from the non relativistic time dependent Schrodinger equation and then treated the partial derivative of time as the partial derivative of position and then he had to change the $H$ and the $E$ to make them compatible with SR.However I dont see the problem in writing a equatio... |
We all know from General Relativity theory that movement of objects around, for example, a star actually straight in spacetime continuum. It just time distortion causes the movement to curve.
Considering this, I have the following questions:
Do planets experience coriolis effect in terms of rotation around a
star?
And... |
Suppose I have a cylinder tank with R radius and height h, and water filled with water up to the level h. There is a vertical rectangular slot on the surface with sizes h x 1 cm. There is only gravitation, no air resistance etc.
Obviously, a jet flowing from the small hole will have parabolic trajectory. But I want to... |
The heat kernel coefficients $b_{2k}(x,y)$ of the covariant Laplacian in an $SU(2)$ instanton background (for simplicity let's say $q=1$ topological charge, so the 't Hooft solution) on $R^4$ is usually presented for the lowest few $k=1,2,3,4,5,\ldots$ in papers, reviews and books. For simplicity let's stick to $k>1$ a... |
my question is as I believe quite simple since I'm new to physics. However here it is: if we take a double slit and constantly shoot helium atoms on it with a constant speed one by one we will see a certain interference pattern on a properly set up screen behind the double slit (scenario 1). If we now set up a detector... |
I am learning about relativity and am interested in time dilation. I now exactly understand where the formula of kinetic time dilation comes from and wondered about gravitational time dilation. I have some questions about this
The formulas of both resemble each other. I think v in the formula of kinetic time dilation ... |
Imagine a pulley (with non-negligible mass) with two masses hanging from the pulley on a rope on opposite sides. One mass is accelerating downward and the other mass is accelerating upward. We assume that the rope does not slip relative to the pulley during the motion. In this case, the tension force on each mass canno... |
The holographic encoding interpretation from the Bekenstein-Hawking entropy is due to it scaling with the area $S_{BH} = A/4$ of the surface, rather than the volume $V$. While I am aware that most quantum systems have volumetric entanglement entropy, I cannot really find any 3 dimensional result for the von Neumann ent... |
When one wants to calculate the two-point-function for an electronic system with Coulomb-interactions in quantum many body systems with the path-integral-formalism
$$
\mathscr{G}_{ \alpha , \alpha^{ \prime } } ( \tau ) = - \langle \psi_{ \alpha} ( \tau ) \overline{\psi}_{ \alpha^{\prime} } ( 0 ) \rangle
$$
which becom... |
I am trying to show that the interaction picture represents a valid picture. We use this picture when our Hamiltonian takes the form $H = H_0 +H_1$. "Valid" means that it should reproduce the predictions of the canonical Schrodinger picture and, following Ballentine, that this "reproducing" is implicit if we can show t... |
There are many situations where a photon is emitted from a charged particle because it accelerates. This includes bremsstrahlung, which is usually a charged particle scattering of a nucleus and losing energy through radiation. And we have an electron radiating photons in a magnetic field because the electron is acceler... |
I'm trying to solve the following problem:
A particle with electric charge e moves with 4-velocity $U_{\alpha}$ in a spacetime with metric $g_{αβ}$ in the presence of a vector potential $A_µ$. The equation describing this particle’s motion can be written
$$U^{\beta} \nabla_{\beta} U_{\alpha} = e(\nabla_{\alpha} A_{\bet... |
A degenerate quantum error correcting code is one in which distinct error operators (e.g. $E_1$ and $E_2$) apply the same transformation to the code's logical states (i.e. $E_1|\psi_L\rangle = E_2|\psi_L\rangle$ for $|\psi_L\rangle$ in the code space). These aren't too uncommon; even the Shor code is degenerate ($Z_1$ ... |
Is there any other way to measure time without using any type of periodic motion. I think it's a no.
A clock is essentially a periodic motion in which we measure some type of periodic displacement. I can't imagine any physical measurement that doesn't use the displacement at its core and since displacement and momentum... |
One sunny day my kids asked me about the light circle (see photo below) they noticed on a small wooden bench in a dark room with no windows (there are just doors to other rooms and kids usually sit on the bench when we come in). The colours was like from rainbow.
We tried to trace the path of the light - it brings us t... |
I'm trying to intuitively understand proper time which is defined as the time that is always measured in a moving observer’s or particle's rest frame and is given by the equation
$\Delta\tau = \sqrt{1 - \frac{v^2}{c^2}}\Delta t$, where $\Delta t$ is the coordinate time.
My confusion stems from the following, if proper ... |
The standard derivation in obtaining a single wave equation involves making use of the heat equation with a Taylor expansion of the equation of state, then differentiating this equation and the continuity equation with respect to time, and combining with the divergence of the NS equation.
From the literature I have fou... |
Consider a wheel attached to an axle.
Since the torque on both must be the same:
$$F_wR_w=F_aR_a$$
$$F_w < F_a$$
because the radius of the wheel is greater than radius of the axle.
My question is: What horizontal force does the axle exert on the wheel?
My ideas: the total force exerted on the system must be the force o... |
Just to preface things, this exact question has been asked before here, but I don't feel like the answer really clarifies things for me.
The core issue is that we want to construct a 4-vector that we can contract with $\partial_\mu$ to form a Lorentz invariant kinematic term we can introduce in the Lagrangian. Schwartz... |
I've heard that there is no limit to photon density. So if we have a bunch of photons going in the same direction, or with some going in opposite directions but with arbitrarily low energy(so that a black hole doesn't form), then can we in theory make a measurement and measure arbitrarily many photons at one point in s... |
The equivalence principle tells us that in some local neighborhood, every free-falling observer in a general relativistic spacetime will measure the speed of light to be $c$; this literally means at a given tangent space, a light beam's 4-velocity is a null vector. Following the geodesic postulate, it will go on its me... |
Consider the free scalar theory with the zeroed Hamiltonian (i.e. such that the vacuum energy is zero). What is the energy of a multi-particle state $\phi^n|\Omega\rangle$ or (perhaps the more physically meaningful normal-ordered) $:\phi^n:|\Omega\rangle$? (where $\phi$ is appropriated smeared such that it is localized... |
What is the voltage induced on the outer shield/sheath by the current of the inner phase conductor in a concentric cable?
The radius of the inner phase conductor is r, the distance from the center of the phase conductor to the shield/sheath is d, and the inner space is air.
Also, not three-phase, only single-phase.
|
https://arxiv.org/abs/hep-th/0111270 by O.Y. Shvedov tries to relate the 'group averaging procedure' (see https://ncatlab.org/nlab/show/group+averaging and references therein) to the BRST formalism so that group averaging can be made sense of for open Lie algebras.
I have a question about the technicalities of the pape... |
Why is the induced voltage due to the current of the phase conductor wrapped around the shield not included in the voltage calculation formula induced by the shield/sheath in the three-phase coaxial cable?
As shown in the equation below, the voltage induced in the a-phase shield/sheath surrounding the a-phase conductor... |
I have doubts about whether chemical equilibrium is possible outside phase coexistence lines on phase diagrams.
I understand that on coexistence lines, chemical potentials of two phases are equal but what happens to chemical potentials outside coexistence lines?
Consider the phase diagram for $H_2 O$
In the water-stea... |
So I was trying to find the electric potential at any point $\boldsymbol{x}$ of a charged wire of length $L$ at the $z$ axis, from $-L/2$ to $L/2$, and I had to write it down in terms of elliptic integrals. Thing is, the potential formula is
$$\phi(\boldsymbol{x}) = \dfrac{1}{4\pi\epsilon_0} \int \dfrac{\rho(x')}{|\bol... |
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