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In Quantum Field theory by M. Schwarz, the author in the introduction of chapter 12 on Spin Statistics theorem says, while describing identical Particles:
Let $$|s_1p_1n_1,...,s_3p_3n_3\rangle \tag{1}$$ be some state consisting of $n_1$ particles with spin $s_1$, momentum $p_1$ and similarly $n_3$ particles with moment... |
So, I have been studying thermodynamics for a while and some mathematical steps involving partial derivatives have now started to hurt my head.
First of all, I understand that whenever we take a $PVT$ system, there are only two independent variables for any process to occur. Using those two variables (choice is ours), ... |
In the book "Relativistic Quantum Mechanics An Introduction To Relativistic Quantum Fields" by Luciano Maiani Omar Benhar, page 174, the picture of that page is provided below.
I don't understand how 12.9 will give 12.10 by the indicated substitution of 12.7.
I tried rewriting 12.9 into $\bar\phi\gamma^0P^+\gamma^0\gam... |
In the last passage of 1975 paper Hawking tells that we can't use a local stress-energy tensor to tackle the backreaction of radiation since creation of particles is a non-local and global process while $T_{\mu\nu}$ is a local quantity, so we can't use it in EFE $G_{\mu\nu}=\kappa T_{\mu\nu}$ to get the dynamic nature ... |
Say I have two objects (we'll call them object $1$ and object $2$) of the same material but of a different colour, placed at the same distance away from another object (we'll call object $3$) that radiates only infrared. Will the fact that object $1$ and $2$ have a different colour cause different absorptions of infrar... |
Fluids obey the Bernoulli equation :a fluid will move from a high pressure area to a low pressure area. If we have a box with a pressure of 2 atm and we open it air will flow from the box to the atmosphere.
And due to conservation of momentum the box will start travelling to the opposite direction of the flow of air.
U... |
Here's the problem (From here):
"A large man sits on a four-legged chair with his feet off the floor. The combined mass of the man and chair is 95.0 . If the chair legs are circular and have a radius of 0.5 at the bottom, what pressure does each leg exert on the floor?"
So, from the explanation, if we want to find t... |
As I understand it, there was initially two formalism for QM, before Dirac reunites them both with his famous braket notation:
Schrödinger's formalism that involved differential operators acting on wave functions,
Heisenberg's formalism that involved linear operators acting on vectors.
Now, if we consider a scalar ... |
Why is 1000 micrometer not a correct representation of a prefix?
I ask because I recently took an entrance exam with a multiple-choice question which went along the lines of
which of the following is not a correct representation for prefixes: (A) 1mm, (B) 10km, (C) 1000 micrometer, (D) Both A and B.
and the stated an... |
Let $a^\mu$ be a spacetime vector in 2+1D: $(t,x,y)$.
What would be the spinor-matrix representation ${A^\alpha}_\beta$ of the spacetime vector $a^\mu$?
I have not been able to even find examples or clear definition of a spinor matrix. Any help is greatly appreciated.
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Why does electric potential definition need to distinct a positive test charge since the result will be the same even with a negative test charge? We could define electric potential with agnostic sign of test charge.
Page 687 from Halliday-Resnick 10 edition: "the electric potential is the amount of electric potential ... |
consider a particle in a central potential, i.e. the potential $V$ only depends on the distance $ r = \| \vec{x} \|$ to the origin. The equation of motion thus reads
$$ m\ddot{\vec{x}}=-\frac{\partial}{\partial \vec{x}}V(\vec{x})=-\frac{\vec{x}}{r}\frac{dV(r)}{dr} \tag{1}$$
We also know that the angular momentum is con... |
It is known that in superelastic collison the energy of particles after collison is more than the original particles but how is it possible . I barely could find suitable information on net for a high school student . These are some conceptions I have about such collisions
these collisions must be endothermic or I sh... |
From a pre-academic studies book, the example uses a gaussian surface outside of the charged sheet to show that because the flux through it is 0, the field on both ends has to be equal. Is this a valid use of Gauss's law?
|
My task is to compute the gravitational intensity $E(\vec{r})$ inside Earth.
I can use the spherical symmetry of the task to use $\vec r = (r, 0, 0)$ (here $\vec r$ is inside Earth), I integrate over all points in the form of $\vec {r'} = (r', \varphi', \theta')$.
By definition,
$$E(\vec r) = A\int_0^{\pi} \int_0^{2\pi... |
The tensor $F^{\mu\nu}$ is defined as $\partial^\mu A^\nu-\partial^\nu A^\mu$. Why is the equation
$$\epsilon_{\mu\nu\rho\sigma}\partial^{\rho} F^{\mu\nu} = 0$$
identically satisfied by $F^{\mu\nu}=\partial^\mu A^\nu-\partial^\nu A^\mu$?
We have
$$\epsilon_{\mu\nu\rho\sigma}\partial^{\rho} (\partial^\mu A^\nu-\partial^... |
I was reading the intrinsic equation of common catenary , where the author assumes tension in the catenary and proceeds.
Why does a freely hanging rope with uniform mass per unit length has tension ? This is contradictory to the fact we use in solving problems in mechanics i.e. when the rope becomes slack, we take the ... |
i just began to study special relavity, and i'd like to know if i made some mistake in one of the questions of the book i solved. the question is:
If we have to events A and B with timelike separation, show that the proper time
$${\Delta}{\tau}=\int_{A}^{B}d{\tau}$$ is maximum when calculated along a straight line
He... |
I have a naive question on how Bosons interact with Fermions.
In quantum field theory, it is stated that the Fermions interact with each other by exchanging Bosons. That means, at a given time, a given Fermion state $\psi_f$ interacts with a Boson state $\psi_B$. My naive question is: is there a direct way to model the... |
The question in my assignment: Suppose we have a tensor $A^{\mu\nu\alpha\beta}$ in four spacetime dimensions. This tensor is antisymmetric in the first two indices, i.e., $A^{\mu\nu\alpha\beta}=-A^{\nu\mu\alpha\beta}$ and symmetric in last two indices, i.e., $A^{\mu\nu\alpha\beta}=A^{\mu\nu\beta\alpha}$. Determine the ... |
Given the energy-momentum tensor for a perfect fluid:
$$T^{\mu\nu}=(\rho+p)u^{\mu}u^{\nu}+pg^{\mu\nu}\space\space\space\space\space(1)$$
I was trying to obtain Euler´s equation:
$$ (\rho+p)u_{\lambda;\nu}u^{\nu} + p_{,\lambda}+p_{,\nu}u^{\nu}u_{\lambda} = 0\space\space\space\space(2)$$
and here is my attempt:
$$T^{\mu\... |
in that problem why didn't we simply put F2=800 and the angle=60
|
From this discussion How can we define a potential for a moving charge? we know that we cannot define a scalar potential (as in electrostatics) in the case of moving charges as described by G. Smith:
You cannot describe the electromagnetic field of a moving charge as the gradient of a potential. If you could, the cur... |
Many sources I've seen have alluded to:
An exciton can form when a material absorbs a photon of higher energy than its bandgap
I looked at absorption enhancing effects of excitons, and am aware of the Hydrogenic series for an exciton. It seems to me that the absorption of light energy below the bandgap is due to exci... |
I feel like I am missing something simple here, but how exactly are gaussian surface determined? Looking at the case of a charge outside a sphere, why don't we pick a gaussian surface not including the sphere itself. Would then the flux inside this sphere be zero? Would that not mean the electric field is zero, since ... |
Question 3.7 b) from Quantum Mechanics: Concepts and Applications by Nouredine Zettili, on page no. 188 (solved examples) - I understand all the solutions mentioned therein but can't figure out why does the following solution give the wrong answer (What am I missing?)? -
$< \psi _0 | \hat {H} | \psi _0 > = < E_3 \phi _... |
From what I understand so far, we live in a 3rd dimension, and we see in the third dimension. We can imagine both the third, second, first, and even the zeroth dimension with thought. However, the fourth and negative dimensions are much harder to understand since we are not able to directly observe them.
My personal hy... |
I have a few basic queries regarding a proof in the set of notes MIT: Open Quantum Systems, the following is stated:
We can derive the Lindblad equation from an infinitesimal evolution
described by the Kraus sum representation with the following steps:
From the Kraus sum we can write the evolution of $\rho$ to $t + \... |
Energy production in stars occurs mainly when a nucleus absorbs a proton or fuses with another nucleus. Some examples:
(i) $\rm{p}(\rm{p},\rm{e}^+\nu)\rm{d}~$ and $~\rm{d}(\rm{p},\gamma)^3\rm{He}~$ and $~^3\rm{He}(^3\rm{He},2\rm{p})\alpha~$ in the ppI chain in the Sun;
(ii) $2\alpha\to\rm{Be}^*$ in the triple alpha pro... |
I know that the n-p-n transistor is faster than p-n-p transistor. My book explains it with 'the hole is faster than an electron. But I think the hole is empty space of electron, so these speeds should be perfectly the same.
Why is faster n-p-n transistor than p-n-p transistor?
|
I am extremely curious about instantons in the context of mathematical physics, and I would like to learn more about the subject. Could anyone give me good references about this? Especially references of modern research articles.
|
Consider two frames $S$ and $S'$ that are related by a Lorentz transformation.
The wavefunction in $S$ is $\psi(x)$ where $x$ is the spacetime coordinates. In $S'$, the transformed wavefunction is $\psi'(x')$.
If the wavefunction in $S$ has a value of $A$ at a spacetime point $x_1$ (i.e. $\psi(x_1)=A$), does it also m... |
When solving collision problems related to the conservation of momentum in my applied maths course, the question of whether the collision was elastic or not is often asked. A lot of them time (such as when a car and a truck collide) the collision is inelastic, even though momentum was conserved.
It is then explained to... |
I don't think I can further elaborate this. It's pretty straight forward.
If we know something (say a tortoise) to exist at two points in time, then can we rightfully assume that it has existed everywhere in between that time period? Or let's say you open a box and find a cat in it. Then you close ... |
The entropy of a Schwarzschild black hole is located near the horizon, and the moment of inertia of a Schwarzschild black hole is $MR^2$. Both aspects imply that the mass of a Schwarzschild black hole is distributed around the horizon, or at least near it.
But a Nobel prize was just given, in 2020, for a black hole sin... |
If everything in the universe were revolving around an axis, how would that affect space-time? In my mind it would be no different from a normal universe since it would look normal in a comoving frame, but I want to get an insight from someone more knowledgeable on the subject.
|
Consider the free scalar field generating functional
\begin{align}
Z&=\int\!D\varphi\, e^{ -\frac{i}{2}\int\!d^4x\, \varphi(\partial^2+m^2)\varphi +J\varphi }\\
&:=\lim\limits_{N\to\infty}\left( \prod^{N-1}_{k=1} \int d\varphi_k \right) \exp\left[ -\frac{i}{2}\int\!d^4x\, \varphi(\partial^2+m^2)\varphi +J\varphi\rig... |
Question:- Two circular coils of radii '$a$' , having resistance per unit length $\lambda$, are moving with uniform speed '$v$' along x-axis as shown, in a uniform magnetic field $\vec B=-B_0\hat k$. At t=0, separation between their centres is just greater than $2a$. Find the force on any one circular ring when $\angle... |
For the Lorentz transfomation matrix elements ${\Lambda^\mu} _\nu$ and inverse Minkowski metric elements $\eta^{\mu\nu}$, how can the relation
$${\Lambda^\mu}_\rho\Lambda^{\nu\rho}=\eta^{\mu\nu}$$
be shown to be true?
I first tried to create a $\eta$ element:$${\Lambda^\mu}_\rho\Lambda^{\nu\rho}={\Lambda^\mu}_\rho(\eta... |
For a may electron atom, a closed subshell structure implies $$L=S=0$$ and therefore also, $J=0.$ Therefore, the ground state wavefunction of such an atom is spherically symmetric because the rotation operator does not alter the state. I understand this mathematically.
But physically, why should this be true? If we con... |
XY is a straight wire carrying current I. Every point on XY will form magnetic field lines in the form of concentric circles in a plane perpendicular to the plane of XY. I know that some magnetic field exists at point A with a direction of into the plane of the screen. But no magnetic field lines are there as the conc... |
So my question is probably quite basic, but I have found this paper online.
http://www.astro.lu.se/~david/teaching/SPH/notes/annurev.aa.30.090192.pdf
And it defines the rate of change of thermal energy per unit mass as:
$\dfrac{du}{dt} = -\left( \dfrac{P}{\rho} \right) \nabla \cdot \mathbf{v}$
Where $u$ is the internal... |
In mechanics, the only physical route a particle can take is the one where action is minimized. Why is this true? Is there a proof?
|
I'm planning an experiment, but due to cost and other circumstances, there will only be one realization of it. So the plan is to collect as many different types of data as we can with a variety of techniques and sift through it. However, I'm not sure how to address quantifying or estimating the uncertainty in any given... |
Suppose i have, in one spatial dimension, a unique ground state $\Omega$ of a local, gapped, translational invariant Hamiltonian. Denote by $\sigma_s$ the density matrix of $\Omega$ on lattice sites $\{1,...,s\}$. I deal with a certain functional, namely
$$
f(s) := \text{Tr}_{\{1,...,s\}}(\mathcal{N}(\sigma_s) \sigma_s... |
I'm looking to create a model using a reasonable physics-based approach to estimate calories burned for arbitrary movement.
To keep the scope fairly limited and tractable, I am looking at the displacement of limbs over time, tracked in real time. Imagine, for many points in time, comparing and accumulating movement dif... |
In the Lumerical tool, I'm simulating a setup using a broadband dipole signal. It is (or should be) centered at $\lambda=$ 922.5 nm and has various bandwidths $\Delta \lambda$ for different simulations. Below, you see the signal as it is submitted to the simulation region for $\Delta \lambda=$ 100 nm (first three graph... |
(note: this is not a school project but a thing I'm trying to do in my free time) I am trying to model 3 point basketball 'swish' shot. A 'swish' is when a point is scored without the ball touching the rim or the backboard. My goal is to find what initial velocity and initial spin (which will be a backspin) can maximis... |
The non relativistic Schrodinger equation of the harmonic oscillator in dimensionless variables is
$$\frac{d^2 \Psi}{d \xi^2} = (\xi^2 - k)\Psi$$
where
$$k \equiv \frac{2E}{\hbar \omega}$$
According to this stack a direct power series solution is a correct way to solve this equation. So I tried substituting $\Psi = \su... |
It was mentioned by N.Arkani-Hamed https://www.youtube.com/watch?v=uPrlD0vorzk that Mandelstam variables in Minkowski signature $(+---)$ do not cover that whole allowed space of $s$, $t$, whereas in some other signature, namely, $(++--)$ they do.
My question is - How can one see the domain of $s$, $t$ of dissallowed va... |
I've read a claim about POVMs in my lecture notes, which I fail to prove. Hence, I would be grateful if some of you have some hints for me /can help me.
Let $\{N_i\}_{i=1}^{d^2}$ be an informationally complete POVM on $Herm(V)$, where $V$ is a Hilbert space. We define its dual frame $\{D_j\}_{j=1}^{d^2}$ by requiring $... |
While calculating S-matrix elements $$\langle\Omega|T \{ \phi(x_1)...\phi(x_n) \}|\Omega\rangle=\frac{\langle0|T \Big\{ \phi_0(x_1)...\phi_0(x_n) e^{i\int d^4x\mathcal{L}_{i}[\phi_0]}\Big\}|0\rangle}{\langle0|T \Big\{e^{i\int d^4x\mathcal{L}_{i}[\phi_0]} \Big\}|0\rangle}$$
Bubble diagrams come from the numerator when d... |
I want to prove that the magnetic field inside a cylindrical cavity in a long, cylindrical conductor carrying uniformly distributed current i and having radius R is uniform. The radius of cavity is 'a' and it's axis is parallel to the main conductor axis. However the axis of cavity is not coaxial with main conductor.
M... |
A bit of a hypothetical situation for y'all here.
Let's say you want to test a video game's accurateness with regards to its physics; by seeing how closely the game's physics matches up with real-life physics (uses the same equations, and relations).
You don't have access to any of the game's code or physics processing... |
In most simple terms, Bernoulli's principle dictates that
a fluid or gas moving in one direction exposes less pressure in orthogonal directions.
the sum of the pressures, in the direction of movement and otherwise, is equal the pressure as measured in rest.
Essentially, we loose static pressure and gain dynamic press... |
Suppose an object is subjected to a force of constant magnitude, which is always directed to the origin. And suppose we know the initial position of the object relative to the origin, and the initial velocity of the object, can we determine if the object will perform uniform circular motion? If so, what conditions are... |
When an electron changes its spin projection in a magnetic field does it receive or take energy?
When the initial spin projection is indefinite (as is according to QM) how much is that energy?
|
My question is may seem vague to some, but for me is a concept I am now learning for the first time (Tensors). I'm now reading from "APPLICATIONS OF CLASSICAL PHYSICS" by Roger D. Blandford and Kip S. Thorne. There in Ch.1 they introduce a the notion of a tensor being a "thing" that accepts vectors as inputs and gives ... |
Consider a two-particle system with Hamiltonian
$$\hat H = \frac{(\hat{\mathbf p}^{(1)})^2}{2m_1} + \frac{(\hat{\mathbf p}^{(2)})^2}{2m_2} + V(\hat{\mathbf r}),$$
where $\hat{\mathbf r} = \hat{\mathbf r}^{(1)} - \hat{\mathbf r}^{(2)}$.
For a little background, let's see how we can handle this in coordinate representati... |
If we ignore the greenhouse effect and imagine all the worlds energy is produced by nuclear or other power plants would the energy needed by humanity to heat be enough to measurably increase the temperature of the whole atmosphere?
In my imagination heating for a few billion people around the world should increase the ... |
I'd like to find the electric field produced by a homogeneous sphere of charge density $\rho$. I know you can use Gauss's law to solve this problem in two seconds. And I know you can simplify the calculation by looking only at points along the $z$-axis, and using the symmetry of the situation to generalize the resultin... |
Say I have a non-Hermitian hamiltonian, such as one might have in an incomplete description of a system where the states are allowed to decay. Then probabilities are not conserved since magnitudes will decrease with time. In particular, say I have an eigenfunction $\mid \psi \rangle$ with $\langle \psi \mid \psi \rangl... |
There is something physically I do not understand, consider this situation:
Lets assume there is no friction. if we defind $x_1$ and $x_2$ the displacement of mass $M_1$ and $M_2$ respectively, we get the equations of motion:
$$
\begin{array}{l}
M_1 \ddot{x}_{1}=-k x_{1}+k\left(x_{2}-x_{1}\right)=-2 k x_{1}+k x_{2} \\... |
In this video it's explained that there is no gravity force, it's all acceleration: Earth moving toward us, but how that's possible without expanding (toward people standing on the opposite sites of the planet) isn't clear (formula's magic doesn't clarify this).
Also this guy disagree and I understand him.
|
Let us assume a charged particle moving in a circle due to a constant magnetic field. Does this particle emit radiation? If so, where this energy comes from?
|
Let's say you're telling the story about two people starting walking toward the north pole from two different points (one from LA the other from NY), they going to walk straight line, but nevertheless they're going to meet at the same point. Trying to explain space-time curvature / relativity.
And after that a person w... |
$Q = mc\Delta T$ (1)
where
$Q = \mbox{heat}$
$m = \mbox{mass}$
$c = \mbox{specific heat}$
$\Delta T = \mbox{change in temperature}e$
$Q = c_vn\Delta T$ (2)
where
$Q = \mbox{heat}$
$n = \mbox{number of moles}$
$c_v = \mbox{specific molar heat at constant volume}$
$\Delta T = \mbox{change in temperature}e$
(1) is used to... |
I read a paper about using femtosecond laser to control a 3-level quantum system. The author wrote the Schrodinger equation for the system and wrote the expression of the laser field. But I still don't know how to put the laser field into the Schrodinger equation.
Below is the Hamiltonian. The author never write anythi... |
More or less the title.
Assume that we have found a box containing a completely isolated system of particles. We do not know for how long this system has been allowed to evolve. We do know what particles the box contains (let's say it's written on the box).
We now decide to open the box and measure the positions of the... |
Say we have a water reservoir with a valve near the bottom to allow water to be released into a separate reservoir (for example, in order to avoid flooding). The valve is initially slightly (10%) open, and they want to open the valve to 20%. What effects will this have on the valve and on the water traveling through it... |
Let us consider a Minkowski space of the form:
$$ds^2 = -dt^2 + dx^2 + dy^2 +dz^2.$$
What would the linearly independent null vectors of this space be?
I am aware this is a trivial question but is something that has not been made clear to me and so causes me some confusion when reading some of the GR literature.
|
An atom consists of 3 parts: Protons, neutrons, electrons. Protons and neutrons go to the center to make up the nucleus, while the electrons go to the outside in the electron cloud. Of the three subatomic particles, there are light particles and heavy particles. Heavy charged particles are all energetic ions with a mas... |
If the thermal radiation of stars is close to the thermal radiation of a black body the sun should appear yellow but yet it appears white because of emitting all of visible wavelengths which combine into white but this is inconsistent with the classification of star colors with respect to their temperatures.
|
since gauss law for electricity is derived from the divergence theorem and couloumbs law. why can it be assumed it is valid for moving charges as coulombs law is only valid for static charges since it has no curl when non moving. so when deriving the wave equation you assume the curl of E is non zero as per faradays la... |
Can someone explain to me or point me towards some references about how can one obtain experimentally a polarized proton beam. I find many talks about using siberian snakes to preserve the polarization of a proton in an experiment, but they don't talk about how you polarize the proton in the first place. Thank you!
|
The authors of the paper "Webs of (p,q) 5-branes, Five Dimensional Field Theories and Grid Diagrams" consider type $IIB$ superstring theory compactified on a circle $S^{1}$ and claim (in page 20) that there is a chain of string dualities between a given $(p,q)$-5 web wrapping the circle, and one $M5$-brane wrapping a $... |
I wanted to make sure that I was definitely understanding the proof of locally flat correctly. I can't see to find a similar proof to the one in the book, so I'm not super sure if my understanding/interpretation is correct. The book that I'm using is "Einstein Gravity in a Nutshell" by Anthony Zee.
Starting with the ... |
The meson particle, Kaon, can decay into pions or leptons + neutrinos. Each decay has its own probabilities as measured and confirmed during experiments.
Has there been any research into the possibility that Kaon particle decay or any particle decay depend on its own surroundings?
There is Bell's theorem and the Hidden... |
I derived the following formula to estimate sunrise and sunset times:
$$ t=\pm\cos^{-1}\frac{\sin\theta-\sin L_{loc}\sin L_{sun}}{\cos L_{loc}\cos L_{sun}} $$
$L_{loc}$ is the local latitude
$L_{sun}$ is the solar latitude
$\theta$ is the desired solar altitude angle (for sunset and sunrise, I used $\theta=0$)
$t$ is ... |
What leads to magnetic monopoles existing before the Inflationary Epoch and becoming infinitely diluted during inflation (if indeed that is the explanation to their absence), but the electric monopoles we know today, namely the quarks and electrons, only forming at the end of the Electroweak Epoch? Indeed, if our think... |
If there was a Universe with nothing but photons, and these photons were all left-circularly polarized, would it stay like this?
(I know this is possible since in a lab you can create a beam of left-circularized light for use with 3D glasses).
But on the other hand we know that massless spin-1 particles have 2 quantum ... |
Stress describes how a body responds to an external force. Or, i.e., stress quantifies the internal force that resists the applied force to maintain a state of equilibrium. So stress, as a vector quantity, should point in the opposite direction to any externally applied force.
In the drawing below, if my hand applies a... |
I don't have any idea how I would go about solving this problem.
|
For an experiment;
A ball is rolled down a ramp and drops off a table
The theoretical and practical horizontal distance of the ball is compared.
Adjustments are made to reach the initial distance
I am trying to use marble tracks for this experiment. I noticed that when a balls diameter is almost the same as the track... |
When the intensity of a light source is measured before and after the light passes through a convex lens, should the two intensity values theoretically be the same? In other words, can a convex lens capture and transmit all photons incident on it by altering their paths only? Or is the ability of a convex lens to captu... |
Can Amperian loop be taken parallel to current. I.e suppose current is in a circular loop in xy plane. And let the screen you are watching is xy plane . Can we take amperian loop in the same plane.
And find out magnetic field at a point .
|
According to the law of conservation of energy:
Energy can neither be created nor be destroyed
Then how did energy come into existence?
|
According to Einstein, mass curves spacetime and objects in the nearby field tends to travel in the shortest possible path to reach their heavier counterparts. My question is was not Newton's interpretation better; i.e. considering gravity as a force that acts on $n$ masses and tends to attract? I know that photons don... |
What can we use in place of relay for very high voltage and current supply switching (let's say 35000 volt).
|
I am reading the Background Field Methods in the EPFL Lectures on GR as an EFT. The authors use this identity on Page 23, Equation (174):
$$
\mathcal{N}^{-1}\int\mathcal{D}\phi\,\mathcal{D}\phi^*\exp\{-i\int\mathrm{d}^4x\,\phi(\square+v(x))\phi^*\} = \frac{\mathcal{N}^{-1}}{\det(\square+v(x))}\tag{174}
$$
which is just... |
I have a setup where I can measure the optical power, in watts, the current, the voltage and the spectrum of an LED. Is it possible from this to calculate the external quantum efficiency? I realise I can calculate the ratio between the optical and the electrical power from this but I think this is a different type of e... |
Let the stochastic process $\{X_t\}$ be defined by the following SDE (Ito's convention for discretization)
$dX_t=\frac{1}{p}S_tg(X_t)dt+\sqrt{2}dW_t$
where $W_t$ is a standard Wiener process, $g: \mathrm{R}\rightarrow \mathrm{R}$ is a $C^{\infty}$ function and $S_t$ is an other (white) stochastic process described by
\... |
I read that bath scales measure body weight and not mass which means they measure m*g and not m.
If I got a reading of 50 kg, does that mean that my mass is nearly 5?
Units of m*g aren't kg so why we say my weight is 50 kg? shouldn't it be called like my weight is 500 N?
|
This is a single ray of an electromagnetic wave propagating in one dimension. But we know an electromagnetic wave travels in three dimensions.
So, I wish to draw the Electric field and magnetic field of an em wave emitted from a spherical source. If I draw the rays, It would be as below.
But Now, if I draw electric F... |
Sometimes I measure LIV curves of many semiconductor lasers with the same material and width and different cavity length.
There should be positive slope and intercept of Threshold current vs inverse cavity length dataset, and also positive intercept of Inverse External Differential Quantum Efficiency vs cavity length d... |
If I have 3 LED lights of following colors and wavengths:
Red 650 nm
Blue 450 nm
Green 550 nm
All three are placed side by side and turned ON.. then what will be the wavelength of the combined light that my eye will see? Most probably the combined color will be 'whitish' because the mixing of RGB colors give white colo... |
Here in the Netherlands we are always trying to get ice as soon as possible so that got me thinking. If you would build a thick layer of ice by spraying a layer of water and wait till its frozen, is it faster to use many small layers or several larger layers. My intuition would say that a small layer would freeze faste... |
Consider this following thought experiment: There are two tracks, one with a line of cameras and another on which a car with transparent sides moves (*). Now, imagine attaching a pendulum to the roof of the car, as the car accelerates to gain speed, we see that the pendulum makes an angle with the vertical in a directi... |
I need to find the equivalent resistance of the circuit here in order to find time constant. I know that I should replace current source with open circuit, then we have this:
That 1k Ohm confuses me. Is it serial or parallel to others? What about 2k and 3k ones? I assume that we should ignore the 1k and then 2k and 3... |
While studying the fundamentals of sound waves in organ pipe, I noted that the fact about phase of reflected waves is contradicting while referring multiple sources
This book of mine describes the reflection from a rigid surface/closed end to be in phase
Whereas this one describes the reflection from a closed end to b... |
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