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Force is defined by acceleration , and acceleration requires the determination of" inertial frames".
But an inertial frames also requires the knowledge of forces which requires measuring acceleration, but with respect to what ?
|
So I am trying to get a more clear picture of what temperature exactly is. Is temperature equal to the microstates divided by the microstates it gains when you add energy $dE$? My reasoning is the following:
$$\frac{dS}{dE}=\frac{1}{T}=\frac{d}{dE}\left(k\ln{\Omega}\right)$$
$$\frac{dS}{dE}=k\frac{d}{dE}\left(\ln{\Omeg... |
The velocity-time graph for the free-fall and rise of a body after hitting ground is given as:-
In this diagram, at $t = 5$ units, the velocity has every value between $5$ and $-5$ at the same time.
This diagram is certainly wrong? So, why is this taught in school?
|
I am reading Witten's article and have a basic question about gauge theory in curved space.
In ordinary flat space (Euclidean space or Minkowski spacetime), covariant derivative of a gauge field $A_{\mu}$ can be written as
\begin{align}
D_{\mu}\phi =\partial_{\mu}\phi +[A_{\mu},\phi]
\end{align}
where $\phi=\phi^{a}T^{... |
We consider an electron "Bob" trying to escape from a metal surface as shown (blue circles represent electrons, red circles represent ions). I know that Bob can't leave the metal surface is because the attraction due to the ions is greater than the repulsion due to the electrons below. My question is: why F(attraction,... |
Suppose I have an equipotential surface S. Thus the electric field at each point on said surface is direction normal to the surface.
Will the magnitude of this electric field be constant for all points on this surface?
(This reasoning comes from the feeling that if the electric field strength were to differ, a closed l... |
I wish to mathematically model the speed of a beaker which is ejecting fluid out of a tiny orifice (area a) at the bottom, as a function of time, t.
[I'll assume the surface area of the beaker to be A >> a, and the container to be extremely light]
At time t,
Let the speed of the liquid layer be u downwards, speed of t... |
I have a couple questions on the mechanism for how solar projection through a telescope works:
I recently took a small telescope focused at infinity, aimed it at the sun, and held a sheet of paper behind the eyepiece. It projected a focused image of the sun onto the paper. When I changed the focus away from infinity i... |
When we solve Klein-Gordon equation, it gives both positive energy solution and negative energy solution. These two solutions are responsible for positive and negative value of $\rho$ which was previously known as probability density in Born's interpretation. But this freedom of $\rho$ of being both positive and negati... |
I'd like to understand the concept of the 2-particle quantum correlator for massive fermions with mass $m>0$ in 1 spatial dimension: $$C(x,y)=\langle 0|\psi(x)\psi^{\dagger}(y)|0\rangle=\int_{-\infty}^{+\infty}\mathrm{d}p\frac{p\gamma^{3}+m\gamma^1}{\sqrt{p^2+m^2}}e^{-ip(x-y)}.$$ While the term in $\gamma^1$ is well de... |
Setup 1: the grounded case
When a positive point charge is near a conducting grounded infinite plate of finite thickness, the area near the charge becomes negative.
The net charge on the plate should be negative:
One way to find the total charge on the plate is to use the method of images (replace the plate with an ima... |
What I mean is that are there any elements which we can actually observe decaying into other elements, like a magical transmutation? Just like how a paper burns into ash.(or some other interesting chemical reaction)
If yes, then please tell me about them.
|
As stated in Wikipedia, the phonon is a quasiparticle, it's the representative of the collective oscillation of the particles which build a crystal. These particles can be atoms, ions etc. The oscillations of the atoms and the spread of these oscillations through the medium, can be associated with a wave, which is char... |
Optical soliton formation in laser systems with devices that facilitate mode-locking such as a saturable absorber help me understand why solitons form in the first place.
However, when one considers a device like a ring microresonator which is simply a dielectric ring, why do solitons form? It has been proven that othe... |
I have a vague notion that thermodynamics is best captured in some language like differential geometry or something of the sort, but I am unfamiliar with said language. That being said, it seems to come up over and over again and, unfrortunately, my lack of knowledge hurts me here. In particular, I am studying Callen's... |
Consider a bipartite quantum system $A\otimes B$ with arbitrary Hamiltonian $\hat{H}$. Consider the partial trace of the canonical ensemble as a function of temperature.
$$\rho_A(T)=Tr_B\left(\frac{e^{-\beta\hat{H}}}{Z}\right)$$
Consider the function $f$ defined using quantum relative entropy by
$$f(T)=S(\rho_A(0)\|\rh... |
Like the title says: If Earth’s water were composed of pure H2O molecules, without anything else dissolved in it, would the atmosphere still produce lightning? I remember that distilled water is not a conductor, this is why I’m wondering.
|
The electric field of an electron moving in $x$ direction has the field $E_y'=\gamma E_y$ in the $y$ direction (where $E_y$ is the field at rest and $\gamma$ the Lorentz factor).
Why is this stronger field $E_y'$ not observed for a current in a wire?
Problem 5.5 of Purcell: "Electricity and Magnetism" (3rd edition) cal... |
All other things being equal, how does the mass of a pistol's slide effect the recoil imparted to the shooter?
Background: firearm enthusiasts often assert that the larger the "reciprocating mass" the more recoil. I am no physicist, but this seems completely wrong to me. Here is my argument. I would appreciate anyone p... |
When dealing with the Dirac equation in curved spacetime one has to replace the partial derivative with the following covariant derivative:
${\partial_{\mu}}-\frac{i}{4}\omega_{\mu}^{\alpha\beta}\sigma_{\alpha\beta}$
where $\omega_{\mu}^{\alpha\beta}$ is the spin connection. What type of physical field this spin connec... |
Reference: Drazin and Reid
Consider Rayleigh's equation away from the continuous part of the spectrum, which is governed by $$\phi''-\alpha^2\phi=0.$$ Given the shear flow $U(z)=\text{sgn } z$, one has solutions of the form $\phi=Ae^{-\alpha z}$ for $z>0$ and $\phi=Be^{\alpha z}$ for $z<0.$ The authors state that if we... |
And Is it the same than for a proton-proton collision and creation of an antiproton?
|
I've only ever heard about information theory being used in stuff related to probability distributions, which makes sense because information and entropy are related. However, I'm having trouble finding resources on a direct relationship between newtonian mechanics and information dynamics, which is weird because most ... |
From what I have gathered, complete constructive or destructive interference results in all light or no light traveling a given path of an interferometer (correct me if this is incorrect). However, when waves are partially constructive (the waves are mostly, but not completely in phase with each other) or partially des... |
In equations (10) and (11) of this article by Curzon on the adiabatic piston, Curzon uses that a system which is thermally insulated cannot have its entropy decrease (irrespective of anything else conceivably "doable" to the system). Why is this so, or am I misinterpreting?
The crux of the derivation is that we want a ... |
In textbook treatment of the BCS theory, by taking the mean field approximation, we get a quadratic hamiltonian, which can be exactly and easily solved (by invoking a Bogoliubov transform of the fermionic operators). In this way, we get a finite gap for the single particle excitations.
What if we do not invoke the mean... |
I am reading through the paper Magnetic Flux, Angular Momentum, and Statistics by Frank Wilczek (https://doi.org/10.1103/PhysRevLett.48.1144) and had some questions about parts (B) and (C) as labeled in the paper.
The setup: We consider a particle of charge $q$ that orbits a solenoid whose magnetic field runs along the... |
While deriving the Planck's radiation formula, why do we use MB statistics when we calculate the average energy of oscillators? Shouldn't we use BE?
Is this because temperatures concerned are very high and quantum stat goes to classical at high temperatures?
But again, in a similar calculation, while calculating the la... |
It is said that to prove mechanical energy can convert to heat energy, Joule measured the temperature increase of water after a free fall. He did his experiment at some waterfall. Because of the high value of the water heat capacity, the effect is not significant.
Now, could we repeat the experiment at the low temperat... |
I have been trying to derive the expression in Ex.3.3 of Straumann's book for the evolution of the separation vector
between neighbouring curves that are not necessarily geodesic.
The claim is that, for $u$ - the tangent vector field, $a=\nabla_{u}u$ its acceleration and $n$ - the separation vector ($n=v+g(u,v)u$, wher... |
As pointed out by Induced electric field from homogeneous magnetic field in free space points in all directions, a current density must present if we impose a uniform and oscillating magnetic field.
However, current density doesn’t quite make sense to me if there is no charge or conductor in such a space. So, if it’s a... |
In Griffiths' "Introduction to electrodynamics" (3rd edition, page 102) he states that:
since the electric field inside a conductor is zero, boudary condition 2.33 ($\mathbf{E_{above}-E_{below}}=\frac{\sigma}{\epsilon_0}\mathbf{\hat{n}}$) ...yields (Eq. 2.49) $\sigma=-\epsilon_0 \frac{\partial V}{\partial n}$.
This is ... |
I'm trying to use the Virial theorem to determine the mass of the M5 cluster and I need the velocity dispersion to calculate this. Does anyone know where I can find a table with these velocity dispersion constants?
|
It still haunts me that during photoelectric effect, incase the energy ($hv$) of the photons is less than the work function, (ofcourse it doesn't get emitted, heard that a hundered times even after slowly & repeatedly asking my professor) do the electrons still completely absorb that insufficient energy or not absorb i... |
This is a simplified version of one of my previous questions. Let $b_1, b_2$ be two boson operators; their vacuum is denoted as $|0\rangle$, i.e. $b_i |0\rangle = 0$. We can make a canonical Bogoliubov transformation:
$$
\beta_1 = u b_1 + v b^\dagger_2, \quad
\beta_2 = u b_2 + v b^\dagger_1
$$
where $u,v$ are two real ... |
To understand the attractive and repulsive force between two currents, I am looking at two electrons moving parallel and antiparallel to each other.
How can an attractive (or less repulsive) Lorentz force between two charges and its directional dependence be explained?
I would like to understand this in terms of dynami... |
Concerning symmetry in fundamental physics, it is usually said that symmetry indicates that laws of physics are invariant independently of something
For example, time translational symmetry indicates that laws of physics are invariant in time, spatial translational symmetry indicates that they are invariant in space an... |
When dealing with thermal expansion problems I've encountered a situation where I must calculate the change in length of an iron bridge 2km long if the amplitude of temperature changes by 40ºC, considering $\alpha_L = 1.25\times10^{-5} 1/K$.
I used $\Delta L = \alpha_L L_0 \Delta T = 1.25 \times 10^{-5} \times 2 \times... |
What is the basis of the believe that there should be a unified theory which simultaneously gives quantum physics (the regime small things moving very fast) and gravity (the regime of big things moving very slowly)? Is this just wishful thinking?
Are there any people who make a strong case of the possibility that no su... |
I know that in plasma, phase velocity $v_{p}$ is faster than light and group velocity $v_{g}$ is slower than light, for the refractive index of plasma $n<1$. When calculating optical path difference, we have $$OPL=\int_{L}n ds$$
therefore the OPD of plasma and vacuum $$\Delta l=\int_{L}n ds -L$$
which means $\Delta l<0... |
When we combine two Angular Momentum operators $J_1$ and $J_2$, which each exist in the Hilbert Space $H_1$ and $H_2$, $J = J_1 + J_2$, the total Hilbert space for $J$ is $H_1 \otimes H_2$.
In my lecture notes it says $J = J_1 \otimes H_2 + H_1 \otimes J_2$. Shouldn't this be $J = J_1 \otimes H_1 + J_2 \otimes H_2$.
Fu... |
The Bohr radius is defined as
$$a_0=\frac{4\pi\epsilon_0\hbar^2}{e^2m_{e}},$$
which can be regarded as an rough estimate of the ground state atomic orbital 'radius'.
If we go back to fundamentals and consider the wavefunction for the 1s orbital, we can find it has a radius
$$\psi_{1s} \sim e^{-\frac{r}{a_0}}$$
which ... |
I was going through the energy/mass equation and it is said that both of the said quantities are interconvertible. That made me think that if we try putting actual values into the equation, the interconversion is actually very large; speed of light itself is a large constant, and the product of its square and mass of a... |
Can photons form black holes the same way as other matter? If there happens to be enough of them concentrated in an area of space so that enough energy exists within a radius to form an event horizon, will an actual inescapable black hole then come into existence?
|
The other day I managed to derive the generators of the Lorentz algebra from the assumption that the infinitesimal spacetime interval $ds^2$ is invariant under Lorentz transformations $x'=\Lambda x$ with $x$ the spacetime four vector and $\Lambda$ a general Lorentz transformation. I did this by requiring:
\begin{equati... |
By the work-energy theorem, we can justify that the work on a particle due to the net force equals the change in kinetic energy of the particle. In compact notation,
\begin{align}\tag{1}
W_{\text{net}} = \Delta KE.
\end{align}
This seems very useful. However, there are other contexts where work is used.
For example, we... |
*Consider aimimg a beam of free electrons towards an isolated free proton . When they scatter, an electron and a protons cannot combine
to produce a H-atom because
A) Energy Conservation B)without simultaneously releasing energy in the form of radiation
C) Momentum conservation D) Angular momentum conservation
NCERT E... |
How can Dirac neutrinos exist if neutrinos have no charge? As far as I'm aware, the antiparticle of a particle is its charge conjugate while all of its other characteristics remain same. How then can a neutrino be distinct from an antineutrino?
|
The experiment is simple You make a capacitor using superconducting plates. You charge said capacitor. You then discharger capacitor through another superconductor. It would seem that you have destroyed energy.
|
Given a metric tensor, you have an Einstein tensor associated with it. If your Einstein tensor is diagonal, you can "match it" with a diagonal energy-momentum tensor. More over, if your metric is diagonal, the energy-momentum tensor will be too.
But this question relies on the physics of the act, when one chooses to wr... |
Considering an EFE like:
$$\begin{pmatrix}G_{00}& 0 & 0& G_{03}\\0 &G_{11} &0 &0\\ 0&0 & G_{22}&0\\ G_{30}& 0& 0&G_{33} \end{pmatrix} = 8\pi\begin{pmatrix}T_{00}& 0 & 0& T_{03}\\0 &T_{11} &0 &0\\ 0&0 & T_{22}&0\\ T_{30}& 0& 0&T_{33}\end{pmatrix}. \tag{1}$$
then, write it in a tetrad frame:
$$\begin{pmatrix}G_{\hat{0}\... |
Good day, everybody.
I program a simple computer game and there is a "dumbbel" inside of it, which should using some kind of rocket engine. The engine is fixed on one side of the dumbbel and creates a constant force F, which is ALWAYS orthogonal to the dumbbel.
Since the dumbbel is ideal, the both sides have only mass ... |
Hawking famously relates the entropy $S$ to the surface area of a black hole $A$ as $S=A/4$. Should I be thinking of the entropy as the number of possible configurations of a spin connection at the event horizon? Is there some ergodic process that is supposed to be stirring the spin connection, so that it becomes a uni... |
In the literature on effective field theories, one might see statements like ''Term X in the Lagrangian is Lorentz invariant but spontaneously violates diffeomorphism invariance''.
When such a statement is made, does this mean it is possible to separate out the term into a sum of two terms, the one which is Lorentz inv... |
I considered light-atom interaction in nonlinear cavity case. This situation is described by Buck-Sukumar model:
$$
H = {\omega}_0 \sigma_z + {\omega}(a^\dagger a) + g \left(\sqrt{(a^\dagger a)}a^\dagger \sigma^- + \sigma^+ a \sqrt{(a^\dagger a)}\right)
$$
This is special case of Jaynes-Cummings Hamiltonian.
First of a... |
In this question, the answer is given 432 which is double of the expected 216.
This appeared counterintuitive.
Why is the work done by the motor double of the difference in final and initial kinetic energies?Friction is an internal force therefore it should not have any effect on the work done.
The teacher says it is ... |
A lever and a fulcrum is able to to multiply the input force to the output force and trade moving distance for increased force. The same happens in automobile transmissions, taking advantage of high motor RPMs.
What exactly is the physical mechanism behind this? I am very aware you can mathematically prove it, for inst... |
How is the background noise of gravitational waves modeled? Is it a thermal model, giving a stochastic distribution of the curvature tensor (field-strength tensor) in ambient space? That is, every binary star, every orbiting planet, every orbiting black hole or neutron star -- anything that accelerates -- is emitting ... |
I have a Hamitonian:
$$
H = \int d^3r \Big[\hat{\psi}^{\dagger} H_0 \hat{\psi} + \frac{g_0}{2} \hat{\psi}^{\dagger} \hat{\psi}^{\dagger} \hat{\psi}\hat{\psi} - \mu \hat{\psi}^{\dagger}\hat{\psi} \Big]
$$
and a peturbation to the bosonic field operator in the Bogoliubov approach:
$$
\hat{\psi} = \phi_0 \hat{a}_0 + \delt... |
Bargmann's theorem gives the criteria under which a projective representation of a Lie group $G$ can be lifted to a representation of its universal cover. More generally, if this criterion, namely $H^2(Lie G, \mathbb{R}) \neq \{e\}$ is not met, then we can lift the projective representation to a representation of a cen... |
This is sort of a 2 part question that I'm really struggling to figure out.
When white light (which as far as I understand, is just a composition of most electromagnetic frequencies) bounces off, say, an apple, a red frequency is reflected and all other frequencies are absorbed. How does this happen? I read this, but ... |
This is what I mean by a pitot tube:
except, the bent tube should be closed, so there is no velocity in the pitot.
But why is there no height? It's reflected in the Bernoulli equation that the small tube and bent one do not have height therefore the static pressure coefficient cancels out. Why is that?
$$\frac{1}{2}\r... |
For example, if we really wanted to, could we, at least in principle, model electromagnetism just considering interactions between charged particles without using the EM field? That is, is it possible to predict all the same experimental results without bringing in the EM field (or the gravitational field, in gravitat... |
I realize the dipole would have to be small enough (in the nucleus of an atom range) and we don't have any mechanism that is small enough to demodulate the frequencies at this rate. But is there some other way to build a machine that would use this form of communication?
I have heard information that if ET are communic... |
The speed of light in special relativity is a constant, 186,000 miles per second, but in general relativity, "the speed of a light wave depends on the strength of the gravitational potential along its path" (Shapiro, qtd. in Wikipedia).
How much energy or mass would be needed to have a gravitational potential strong en... |
Was reviewing some notes on fluid dynamics, and the notes go as follows (conservation of mass for a qubic CV),
$$\frac{dm_{out}}{dt} = \rho u (dydz)_{x+dx} + \rho v (dxdz)_{y+dy} + (similarly,forZ) = \rho u dydz +\frac{\partial \rho u dydz}{\partial x} dx + (similarly,forYandZ)$$
I don’t understand what the $x + dx$ su... |
I am working on a term paper for a physics class and I am studying the acoustics of nightclubs. The only issues I've run into is I found it difficult to find many sources on the types of materials and sizes of nightclubs. I also found it difficult to find research on how speakers are arranged in nightclubs. I was wonde... |
Books such as 'Quantum Theory of Light by Rodney Loudon (page 140)' and 'Quantum Optics for Beginners by Ficek and Rizda (page 43)' claim that the multimode state is nothing but a tensor product of single-mode states, but doesn't this mean that there can no be correlations between photons?
Do they actually want to mean... |
What I know about this topic
From books I know that in ancient times the Greeks did experiments such as rubbing two glass rods with wool to make them repel each other, rubbing two plastic rods with fur to make them repel, and bringing a glass rod and plastic rod (already rubbed) to make them attract each other. Based ... |
In many articles, the $C_3$ Rotation matrix is expressed as $U=e^{i\frac{2\pi}{3}\sigma_z}$,where $\sigma$ is the pauli matrix in sublattice space, the symmetry of the tight binding hamiltonian is expressed as $UH(k)U^\dagger=H(C_3k)$, but I don't understand why
|
While reading the Wikipedia article on Drag Crisis, I found:
The drag crisis is associated with a transition from laminar to
turbulent boundary layer flow adjacent to the object.
While, the Wikipedia article on Turbulence states:
In general terms, in turbulent flow, unsteady vortices of many sizes appear
which inter... |
Suppose you are in space (or on a frictionless surface) next to another object of the same mass $m$ as you. Take the reference frame of the center of mass of you and the object (so there is zero velocity initially). Now suppose you push on the object with a constant force $F$ for some time $\Delta t$ to "jump off" the ... |
Let's say the lagrange function of my system is $L = T(z,\dot z) - m g z$ and I want to determine the equations of motion.
Why is $\frac{\partial L}{\partial \dot z} = \frac{\partial T(z, \dot z) }{\partial \dot z}- 0$ ?
I want to know why the second term is 0 even though it is obviously dependent on $\dot z$, since $... |
A point charge $Q$ is brought to a position a distance $d$ away from an infinite plane conductor held at zero potential, now calculate the surface-charge density induced on the plane.
The book always writes we use the method of image, so the surface charge density,$ \rho_s$, is $$ \epsilon_0 \frac{Q}{\epsilon_0 4 \pi}\... |
How to calculate the size for Cooper pairs?
|
A flute is a wind instrument in which the interaction between a player supplying a modulated jet stream and the column of air in the cylinder result in the formation of longitudinal sound waves.
The sound spectrum of the flute comprises the fundamental wavelength and harmonics which are integer multiples of the fundame... |
I have to work with the radial velocity dispersion. Could someone help me to understand what this actually is and how I work with velocity dispersion? What happens if you multiply the radial velocity dispersion with the radius? Is this something that is often done? In which systems does the radial velocity dispersion c... |
Confusion arised out of reading this answer, it says
You can immediately describe the 2 particles by their center of mass description (an atom) plus their individual attributes (i.e. what the particles are doing within the atom). Assuming the 2 particles start off at rest, then they are in a bound state already becaus... |
I was reading introduction to modern cosmology by Andrew Liddle. On page 56 he shows a graph of the $\Omega_{\Lambda}$, $\Omega_{0}$ plane and there's a region where no big bang is needed, later on the text he says that there's an analytic expression for that curve but it was too complicated to give. I looked for it in... |
In order to derive the conservation of four-momentum of a field, $P^\mu$, it is assumed that the total change in the field, defined as $$\delta\phi_a(x)\equiv {\phi^{\prime}}_a(x^{\prime})-\phi_a(x)$$ is zero for any field, under a spacetime translation $x^\mu\to x^{\prime\mu}=x^\mu+\varepsilon^\mu.$ Here, $\varepsilon... |
How can one calculate the local sky observable from any given point on the Moon, expressed in lunar coordinates? Specifically, I would like to understand the methodology and equations involved in determining the positions of celestial objects such as stars, planets, and the Earth, as viewed from a specific lunar locati... |
If we got an oscilating electron up and down, it will definately produce changing electric field. I won't go into magnetic field topic. Let's only restrict the question to electric field.
Since we got a changing electric field, we know that it produces sin or cos wave. My question relates to how it produces the sin or ... |
I was reading Statistical Mechanics by Mcquarrie and met a function that describes the number of states of a single particle that has equal of less energy than $E$ in a 3d infinite well. The book describes that function by defining the radius $R$ of 3-dimensional space spanned by quantum numbers $n(x)$, $n(y)$, and $n(... |
I am calculating with a vertex connecting a pion, delta and a nucleon. In general, the vertex is calculated as
$$ \Gamma_{\pi N \Delta, a}^{\mu} \sim \gamma^{\mu\nu\rho} (p_\pi)_{\nu}(p_\Delta)_\rho T_a, $$
with $p_\pi, p_\Delta$ the pion and delta momenta and $T_a$ are isospin 1/2 to 3/2 transition matrices. In the n... |
To begin with, please note that I am fully aware of the differences between the confusingly named "first quantization" and "second quantization", and how they correspond to classical non-fields, and classical fields. (thanks for all the great contributions regarding these topics by the way !)
Take the Dirac partial dif... |
I have a knot about the "secondary" colours and its spectra.
So If I look the spectra of white light, I can see that yellow, which is between R and G, has some wavelength. If I do an addition of light of Red and Green, I get yellow. Ok.
Now If I do an addition of light of Red and Blue, I get Magenta. But how come that ... |
Okay, so I have the follow question. I have been bugging my professor for an answer, but his answer confuses me.
Say we have a 1D phonon collision process where two transverse acoustic phonons combine to give one longitudinal acoustic phonon. They have dispersion relations
$$\omega_{TA}=\omega_0\left\lvert\sin\frac{ka}... |
I have been trying to solve the following problem out of Modern Electrodynamics by Andrew Zangwill (Problem 20.8):
A charge density $\rho(\vec{r},t) = q(t)\delta(r) $ where $ q(t) = 0$ for $t < 0$ and $q(t) = q_0$ for $t > \tau$. Calculate E and B using symmetry and elementary methods
I tried to determine the current d... |
We define the dot product of two vectors (A and B) as : a * b * cosθ which usually just says that it is the projection of A vector on B vector multiplied to give a scalar value.
Although, I am not able to digest this idea completely and have these doubts:
What does it actually mean to multiply two vectors? (Like am I ... |
"If gravity working on matter is the only force at work on large scales, then the attactive force of gravity will act to slow the expansion. In this case, the universe was expanding more rapidly in the past than it is now, and the universe is somewhat younger than Hubble time." --- Pg. 16 (Introduction to Cosmology by ... |
I have done some research on lattice QCD spectroscopy, I am familiar with numerical simulations to the point of effectively using the asymptotic behaviour of 2-point functions to recunstruct the spectrum of the theory. The point is that nothing of what I have done in lattice QFT to this point has ever required me to us... |
As long as the time dilation is about what the observers think or see, there would be no great difficulty. But the assertions that the clocks run faster or slower cannot be justified.
|
Background
In Viscous Fluid Flow by White, the speed of sound for a gas is given as
$$\tag{1-71}
a^2 = \frac{\partial p}{\partial \rho}\big|_s
$$
where the partial derivative is computed at constant entropy.
White mentions that a thermodynamically equivalent expression is
$$\tag{1-72}
a^2 =\gamma \left(\frac{\partial p... |
I am trying to develop an analytical model for RF wireless power transfer from an external antenna to an implant antenna, embedded inside layers of lossy tissue.
The external antenna will be positioned at some point in free-space. The dimensions/geometry of both antennas are known. I would appreciate if you could shar... |
Can there be some version of the Fulling–Davies–Unruh effect, in which the accelerating observer is moving with a non-uniform acceleration? Can someone refer some papers to read?
If there can not be such a version of the effect under consideration and we can say that with certainty, which is the reason?
Any help will b... |
I am trying to calculate the second order correlation function $g^2(τ)$ at τ (delay) equal to zero, for a 2 modes squeezed vacuum state that is given by:
According to the following paper https://www.science.org/doi/10.1126/sciadv.aba9186, if you consider the signal or idler photon individually, $g^2(τ)$ should be equa... |
I tried to construct the Wigner-Seitz cell with its perpendicular lines as explained in Wikipedia for a hexagonal (honeycomb) lattice.
(hexagonal lattice [1] with: Wigner-Seitz cell in green, sketched construction lines in blue and primitive unit cell in gray)
I know that hexagonal has a two-atom-based primitive unit ... |
I am wondering if there is an equation for how close you need to compress a mass to make a black hole. I have seen claims that if the earth is shrunk to the size of a golf ball, it would create a black hole. However, I can't find any equations for this size online. Ideally, the equation would take into account the spin... |
The calculation of the autocorrelation function for particles undergoing Brownian motion is described in chapter 7.6 of Chaikin and Lubensky (See picture below). There are couple of things which I dont understand here.
The derivation begins defining $P(x,t|x_0,t_0)=\left<\delta(x-x(t))_{x_0,t_0}\right>$ where the avera... |
My understanding is this: the Solar surface becomes speckled with more sunspots near Solar maximum, and these spots tend to form groupings known as active regions; each spot is associated with a given magnetic polarity, and often regions will tend to have spots of both polarities that are typically linked in certain wa... |
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