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I was reading up some references about QM/QFT and I came across this note (actually a problem set): https://www.classe.cornell.edu/~yuvalg/p4444/hw8-sol.pdf
In question 1, the author mentioned that "In the limit where particle production and annihilation can be neglected, one can use the idea of potentials. In QFT, thi... |
In X-Ray diffraction experiment how the reflected rays superimpose as we know reflected rays are parallel. As we can see in the image
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If we place a Newton cradle 1 km long along the road and now passing on a bicycle hit the first element (sphere) with a hand the speed of the disturbance would be the same no matter how fast the bicycle is moving so the last element will move after the same time interval. Can this be compared with the phenomena of inva... |
I was watching this video and it shows that adding fins on the wing helps the air get turbulent on the upper part of the wing, which forces the air to stay longer, and ultimately this helps with lift.
To my understanding, if we didn't have those fins, the air wouldn't stick so long on the upper wing, leaving an "empty"... |
Although this question has been asked many times here, I haven't found a satisfactory detailed quantitative answer.
The question is:
If an ideal gas container that is moving with a velocity $v$ is suddenly stopped, will the temperature of the gas change?
I've thought about this for many days but couldn't figure out h... |
In statistical mechanics, I'm trying to gain intuition as to how to get an upper bound on an equilibrium expectation value of some observable $F$ in terms of the non-interacting expectation value.
Let's say the expectation value is given by $$ \langle F\rangle \equiv \frac{\int \exp(-\beta H)F}{\int\exp(-\beta H)} =: \... |
When an object is placed in an inclined plane (rough), and the inclination is made to 90 degrees with horizontal. In this case normal contact force is zero, implying that frictional force is zero. But even in this case, intermolecular force and resistance due to roughness on surface is still present . Then why we say f... |
http://farside.ph.utexas.edu/teaching/em/lectures/node94.html states:
So, in the optimum case half of the power absorbed by the antenna is immediately re-radiated. Clearly, an antenna which is receiving electromagnetic radiation is also emitting it.
Suppose I have an ideal isotropic radiator radiating $P_x$ into empt... |
I have read in my physics book that:
$\epsilon\gt1 $ (for all substances)
where $\epsilon $ is Relative permittivity
Why is it that $\epsilon$ is never less than $1$?
|
I'm sure that questions of this ilk have been asked before however I wanted to know if there is some advice for someone from my background. Recently, I've taught myself General Relativity (needed to fill time during lockdown, eh?), reading pretty much cover to cover 'Spacetime and Geometry' (Carroll) and coming up to f... |
In special relativity the 4-tuple of numbers, energy and 3 components of momentum, form a 4-vector with respect to Lorentz transformations.
Is it true that the analogous 4-tuple of energy and momentum of electromagnetic field in vacuum is also a 4-vector with respect to Lorentz transformation?
|
My initial calculations show that if the radius of a star $-$ with a uniform mass density of $\rho$ $-$ is greater than $\frac{c}{2\sqrt{\pi G\rho/3}}$, the star would collapse into a black hole. However, I could not find any reference to check the result. Can anyone help me?
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Let us assume that all we know till now is that two types of charges exist. One of them is possessed by an elementary particle called an electron and the other by another elementary particle called a proton. We also know that the effect of a proton on another proton is the same as that of an electron on another electro... |
Let say we observe two galaxies, one little bit closer to us than the other one. If we calculate the speed of the farther one does it mean that according to the Hubble law when the closer one reaches the distance where the farther one was it will have increased its velocity to match the velocity at that larger distance... |
I'm 15 and just had a question about physics and electric fields.
I've read that electrons flow in the opposite direction to current. Isn't current the flow of negative charge and therefore the flow of electrons?
Or are they referring to conventional current?
|
I was following Sidney Coleman videos and lecture notes where he claimed that unique ground state requires spinless harmonic oscillator. On the other hand spin introduces degeneracy in the ground state corresponding to the various values of the $z$-component of the spin.
Can anyone explain how the degeneracy appear for... |
Let's say we have a Steady-State Disk (Fishbone 1976 HD, or an MHD disk). For simplicity, we focus only on $\theta = \pi/2$.
If we perturb every physical quantity by the rule $A = A+ \delta A $ (where $A= P,B,u,\rho,\rho_e$), could we possibly consider a boundary condition on event horizon, that will help us study the... |
From what I understand, double integrator is a model where some entity can move according to some speed, which depends on the acceleration force exerted on the entity.
If someone would ask me to represent such a model, with $x$ the position of the entity, $v$ its velocity, and $a$ its acceleration, I would write it dow... |
When reading about the history of the discovery of the neutrino I came across the following paragraphs in my lecturer's notes:
(...) physicists were puzzled by the continuous spectrum of $\beta$-decays. In this
process, a nucleus transforms itself into another one with the emission of an electron:
$${}^A_ZX \to {}^A_{... |
Not a physicist. Hope to clarify some conceptual issues I have with non-linear propagation of light through a medium, since I seem to be mixing up some very fundamental concepts. Specifically, I am having some doubts regarding the chirping that occurs during, for example, self phase modulation of a wave propagating thr... |
I don't quite get the concept of drift velocity. According to definitions, it is the net velocity with which the electrons are drifted in a direction opposite to the applied electric field. Is the thermal velocity included in that or is it different? According to what I have read drift velocity goes to zero after each ... |
Context
Let's say we have an infinite potential well of width $L$
\begin{equation*}
V(x) = \begin{cases}
0, \quad x \in [-L/2, L/2] \\
+\infty, \quad \text{otherwise}
\end{cases}
\end{equation*}
The energy eigenstates of a particle trapped in this potential form two distinct sets of even $\phi_n^+$ and odd ... |
In the context of time dependent perturbation theory as in 8.06, video's code L 11.2 from mit ocw, I can't see any Dirac delta function appear anywhere. When I read about "Fermi's Golden Rule". This equation appears at some point:
$$\Gamma _{if}=\frac{2\pi}{\hbar}|<\psi _f|H'|\psi_i>|
^2\delta(E_f-E_i+\hbar\omega).$$
H... |
The particle $m_2$ moves on a vertical axis and the whole system rotates about this axis with a constant angular velocity $\Omega$. Find the Lagrangian of this system.
(Note that there are two $m_1$ in this system)
The solution provided by author is different from the conventional method:
Let the angular displacement ... |
I have this passively cooled mini-PC that froze every few days. After a lot of investigation I realized that it was overheating (running android studio and such) so I bought a fan, an arduino nano and everything else needed to build a fan controller. It works well, my question is why I have to set the threshold tempera... |
Laptop upgrade tutorials advise grounding oneself to metal objects ultimately connecting to literal ground (floor, Earth), such as the laptop's metal case, or a metal door, heater, etc. Is this really necessary? Won't simply touching a charge-neutral conductor such as a spoon suffice? Naturally it has a much lesser "el... |
Please note — this question considers a point-driven Chladni plate, not Chladni's classical experiment. I'm aware of various other questions concerning the latter here on Physics.SE.
As the title suggests, I'm looking to derive a physically correct model of a point-driven Chladni plate. Essentially, this is a plate (t... |
If one were to fly a paper airplane at the Dead Sea (400 meters below sea level) and another identical paper airplane at the peak of Mount Everest (8800 meters above sea level) would there be any noticeable effects on the flight of the airplane? Assume still air with no thermals and flight far from surfaces such as the... |
I have to find out the relation between F and M, if rope is pulled with constant velocity V. Please help, these types of multiple pulley messes up my constraint equation. Thanks.
|
C2 has a charge of 8C and 4F capacitance. C3 has no charge and 2F capacitance. S2 is then closed for a long time.
What is the total Joule heat generated in resistor R2?
The answer is 8J/3 but I'm not sure how to get to this.
What I was asked to do before I got to this question:
Find the charge stored in C3 after S2 i... |
I'm 15 and recently started electronics and I just had a question about batteries.
According to a video I watched by "The Engineering Mindset", a battery creates potential difference by accumulating more electrons on the negative plate. Therefore the more electrons that accumulate on the negative plate, the higher th... |
My physics book introduces dielectric materials by considering firstly the electric effects due to polarization (without taking into account the causes of this polarization). Then the book itself considers the determination of polarization as a consequence of the field acting on the material. In particular, it is said ... |
What is the principle of physics used in this popular stunt?
Initially, I thought aerodynamics due to an increase in the angle of attack, but its magnitude is not sufficient to balance the whole body and skateboard. Please, can anyone help me to get about it?
Animation:
|
If we lift an object of mass $m$ from the ground at $z=0$ to height $z=h$ without acceleration, the lifting force must equal and opposite to the downward force of gravity. The work done by the lifting force is $\vec{F}_{\rm lift}=mg\hat{z}$ is $$W=\int\limits_{\ell=0}^{\ell=h}\vec{F}_{\rm lift}\cdot\vec{d\ell} =mgh$$ u... |
Suppose, in a universe of $n$ particles, the initial position vectors of the particles are $\vec{r_1},\vec{r_2}.....\vec{r_n}$, and their initial velocities are $\vec{v_1}, \vec{v_2}.....\vec{v_n}$
The evolution of these particles over time is given by this law:
$\frac{d\vec{v_i(t)}}{dt}=\sum_{j=1}^n d_{ij}(t) \vec{u}$... |
I'm trying to understand Eq. 2.6 in this paper. I understand the idea and derivation of the SUSY Ward identity itself and I know how to apply it in the $\mathcal{N}=1$ case. What confuses me here is the particular form of the commutation relations between the supercharges $Q^{(\dagger)}$ and the bosonic/fermionic opera... |
Has anyone measured it? I can't seem to find anything online for "spoon capacitance"; what's the expected (self-)capacitance on the typical household utility metal spoon? The spoon heads bear a nice surface area to store charges like a two-plate capacitor.
Alternatively, capacitance of any typical household utility wil... |
Can we use an electric field to rip apart a nucleus? . Let's take 3He which is a very stable isotope but unfortunately not commonly found. And let's assume we have placed an 3He inside a spherical box negatively charged.
The box will attract the protons and because it is spherical this means whatever the orientation of... |
I'm reading a Calculus textbook and it says:
If we are pumping air into a balloon, both the volume and the radius
of the balloon are increasing and their rates of increase are related
to each other. But it is much easier to measure directly the rate of
increase of the volume than the rate of increase of the radius.
W... |
ABC is a right equilateral triangle. An electric charge q is placed at A and an electric charge q' at B. The electric field at C is found to be parallel to the side AB, as shown by the arrow in the figure. Choose the appropriate formula from below which shows the relation between q and q' correctly.
The answer is give... |
Does QM explain the fact that in nature electrons in atoms tend to be in the lowest energy level?
Why are excited states unstable? And are excited states always more energetic than stable ones?
|
The standard method for numerically calculating the Berry curvature of a 2D condensed matter system is given by Fukui-Hatsugai-Suzuki in this paper.
They discretize $k$-space into a grid with tiny rectangles and calculate the Berry curvature on each rectangle using so-called overlap matrices $U_\mu$ and difference meth... |
In the explanation of photoelectric effect it is written that intensity and frequency of radiation have different results i.e. higher intensity means greater number of emitted photoelectrons and higher frequency means greater kinetic energy of emitted photoelectrons.
But what we have learned about intensity is that it ... |
I am trying to verify Equation 2.7.30 from Sakurai's "Modern Quantum Mechanics" 2ed. The bottom line of my question is:
$?? \psi^{*}\vec{A}\cdot\nabla\psi+\psi\vec{A}\cdot\nabla\psi^{*}=0 ?? $
And here is how I arrived at it. Below, all equations straight from Sakurai have (==) and all of my intermediate equaitons just... |
You are given a charged ring and there exists a changing magnetic field whose rate of change is $A$.
I denote the charge on the ring with $q$, and the mass on ring with $m$.
What is the angular acceleration of ring?
|
My physics mentor was teaching about circular motion. To explain it, he used an example of a car moving in a circle with constant speed $v$ having mass $m$. Then he talked about a situation when the car would go out of the track. He calculated maximum velocity as followed:
$$f = \frac{MV^2}{R}$$
$$\mu_s m g = m\frac{v_... |
Is there some condition in wich the water evaporation can cool down the air even if the water is hotter than the air?
|
I am asking a (relatively) 'low-energy' question here, not about things like the Large Hadron Collider...
There are tons of articles everywhere, including such places as Wikipedia and ScienceDirect, that talk at length about probing condensed matter with electrons and neutrons; in addition to EM beams like X-rays...
Wh... |
This question was posted a week ago on MathOverflow https://mathoverflow.net/q/369156/
The Anderson Model is given by the random Hamiltonian (as an operator on $l^2(\mathbb{Z}^d)$)
$$
H_\omega = - \Delta + V(\omega)
$$
where $V(\omega) \mid x \rangle = \omega(x) \mid x \rangle$ with $\{ \omega(x) \}_{x \in \mathbb... |
Using rope with idealized coefficient of surface friction approaching zero, that is in all other ways typical (typically stretchable, compressible, flexible and twistable), is it possible to tighten a true knot, defined here as a “prime knot” according to knot theory, (which excludes hitches such as the clove hitch cov... |
For spontaneous magnetization $m$ in a sample of volume $V$, what do the limiting operations $$
\lim\limits_{V\to\infty}\lim\limits_{B\to 0}m(B,V)=0,\\
\lim\limits_{B\to 0}\lim\limits_{V\to\infty}m(B,V)\neq 0$$ physically mean and why don't they commute? $B$ denotes the applied magnetic field.
|
I believe that at STP, there are no pairings of a liquid and a gas where the liquid will float atop the gas. Even considering very high-density gases, such as tungsten hexafluoride (12.4g/L), and very low-density liquids such as isopentane (616g/L), this seems clearly impossible at standard temperature and pressure.
H... |
It is easy to find equations that quantify this on the internet, but not an explanation as to why...
Also, does this apply to electrons and neutrons? Or just X-ray reflection/diffraction?
|
There are some points in this wikipedia chapter. Main equation is:
$$ T^{\alpha \beta} \, = \left(\rho + {p \over c^2}\right)u^{\alpha}u^{\beta} + p g^{\alpha \beta} $$
where $c$ is explicit.
The one for the trace is:
$$T = 3p - \rho c^2$$
that seems contradictory with:
$$T^{\alpha\beta} = \left( \begin{matrix}
... |
Supposing that the condition of humidity and the temperature are the same. Concretely if in one place on Earth there is the same humidity, temperature, it is more hot in the first part of the summer when the Sun is closer and closer to the Zenith than to last part of the summer (21 June - 22 Sept).
Question:
Is it pos... |
I don't know much about physics but I have a question.
Let's say you were lost in a completely flat desert, with seemingly nothing else surrounding it, and you screamed at the top of your lungs: would you be able to hear any echo/reverberation ?
|
The current density equation states that $J = I/A$.
But I got a question that asking the current density over an infinite plate.
Say the current $I_0$ flows into the infinite plate that extent infinitely on $z$ direction from $x = 0$ to $d$, What's the current density on the plate? The plate in unspecified on $y$.
I ha... |
In QFT, it seems the propagator has a simple closed form in momentum space. The position space representation is more complicated, but could be worse -- basically it's a Bessel function (depending, of course, on what field one is talking about).
Question: What are some applications of knowing the precise analytic form ... |
Check Problem 3.43 in Griffiths Introduction to Electrodynamics
A conducting sphere of radius $a$, at potential $V_0$, is surrounded by a thin concentric spherical shell of radius $b$, over which someone has glued a surface charge $\sigma(\theta)=k\cos(\theta)$ where $k$ is a constant and $\theta$ is the polar angle.
... |
The value of the cosmological constant is $Λ = 1.10 \times 10^{-52}$ m$^2$. What is it saying or conveying in layman's terms other than the obvious that the universe is expanding?
|
Can gravity be focused by large massive objects?
|
Suppose a rod is rotating in a horizontal frictionless plane, hinged at one of its ends. If the body is non rigid, it would change its length, but I am not sure whether it would elongate or get compressed. According to me, it should get compressed, as centripetal force acts towards the centre leading to compression of ... |
In $U(1)$ gauge, the transformation is given by $(c=1)$ $$e^{\frac{ie\int A_\mu dx_\mu}{\hbar}}$$ I know that this form comes from the phase picked up by electrons in Aharonov-Bohm effect. However, in the magnetic Aharonov-Bohm effect, the form is connected with the existence of magnetic monopole. Such a monopole would... |
I'm just starting to learn special relativity, and I'm having trouble with the following concept:
In relativity, units of length and time of moving frame are related to that of stationary one through $$x’=\frac{x}{\gamma}\quad \quad \text{ and }\quad \quad t’=t\times \gamma$$ respectively, where $\gamma$ is Lorentz Fac... |
If work is a product of force and displacement, and force increases as acceleration increases, does these mean that work is dependent on acceleration? For instance, if I lift a block faster, does this mean that I did a greater work?
|
I know it's a regular question, but I'm having a problem with the concept of circular motion.
Intuitively, the earth and people have the same angular velocity，It's because people are standing on the earth.
It looks like a centripetal force provided by a component of universal gravitation, not because of friction.
I don... |
I looked at a few of the other posts regarding the accuracy of atomic clocks, but I was not able to derive the answer to my question myself.
I've seen it stated that atomic clocks are accurate on the order of $10^{-16}$ seconds per second. However, if there is no absolute reference frame with which to measure "real-tim... |
The quantum-mechanical model of atoms was derived from Heisenberg's uncertainty principle, which states that the position and momentum of a particle cannot both be determined to an arbitrary degree of accuracy. In order to understand the distribution of electrons in an atom, the momentum of an electron in the uncertain... |
Let there be a situation where a force 'F' is acting on one end of an in extensible string which is connected to a box named 'A' resting on a friction less horizontal surface through the other end.
The Force F is transmitted through the string and acts on box 'A'. As a reaction to this box 'A' pulls the string toward ... |
What quantity does the area under the stress–strain graph (under the elastic limit) represent? As far as I know, the potential energy density due to strain is 1/2×(stress)×(strain). So does the area under the stress–strain graph represent twice the potential energy density?
|
I'm looking for physical examples of systems which support wavepackets, where the phase speed can be made (very) close to the phase velocity.
I know already that this happens in some optical guides and capillary waves, but do you have other physical examples ?
|
In the figure above, it must be noted that $R-r$ is Infinitesimal small, but it is shown bigger in the figure.
here $y_{cm}$ is $y$-coordinate of center of mass (COM), $m$ is the total mass of the hollow cone.
But now when i saw the correct answer on google it was not the same as i got, can you say what i have done wr... |
My question is quite subjective and I could not find a suitable explanation to whether there is a magnetic field in space beyond earth .I read one of the article stating
Interstellar dust clouds have been found with fields as high as a few milli Gauss; about 1000 times stronger than the Milky Ways average magnetic fie... |
There are different modes present in a multimeter. one is
the current mode and voltage mode for their respective measurements. what
will happen if one try to take a voltage reading by keeping it in current mode?
|
I was trying to solve the eigenvalues/eigenfunctions problem of the Schrödinger equation with Yukawa potential
$$V(r)=-\frac{1}{r}\exp \left ({-\frac{r}{r_0}}\right).$$
I worked, as usual in the case of central potentials, using the substitution $R(r)r=y(r)$, introducing the parameter $k=\sqrt{2|E|}$ and the variable ... |
I have a Master's degree in Theoretical physics, and I've followed a university course on Nuclear Physics. I want to study the subject in more detail. I'm looking for a complete, but a not introductory, book where I can find both theoretical and experimental descriptions about Nuclear Physics. Does anyone have a sugges... |
Let $O$ and $O'$ be two inertial frames where $O'$ moves with velocity $v$ relative to $O$ along the $+x$ direction. A light beam of intersection angle $\theta$ with the $x$ axis in frame $O$ has a different intersection angle $\theta'$ with the $x'$ axis in the frame $O'$. The transformation rule reads
$$ \cos\theta' ... |
In Special Relativity, I know that a Lorentz length contraction and Lorenz time dilation are possible.
But, what about length 'expansion'?
If only length contraction is possible, then, why is the distance greater than 100m (the trains' rest length)?
|
We will use two light sources of exactly the same frequency and same emitting area in this experiment as shown in figure
The distance of both the sources is adjusted to be the same (indicated as d) and in such a way that both project the photons to the area inside the circle ⭕ and also both are switched on at the sa... |
I am aware of this SE-Answer, however, I am eager to know why Heisenberg himself introduced an observation-based experiment to demonstrate his intuitive explanation of his uncertainty formula. Does his microscope experiment show that Heisenberg initially believed that his uncertainty principle had been a measurement ef... |
I’m working in Peskin and Schroeders book on QFT and noticed that they expanded a solution to the Klein Gordon equation in a manner that seems to me not to be be Lorentz invariant even though the solutions to the KGE should be scalars.
The Hamiltonian, being a function of $\phi$ and $\pi$, also becomes an operator. Ou... |
I have two questions regarding chapter 2 of Landau & Liftshitz "Mechanics", on page 14-15.
Regarding homogeneity of time, we have:
$L$ is a closed system therefore $L$ does not depend on time explicitly
$$\frac{dL}{dt} = \sum_i \frac{\partial L}{\partial q_i}q_i + \sum_i \frac{\partial L}{\partial \dot{q_i}} \ddot{q_i}... |
I have a physical simulation of a vibrating string (made with matter.js). From this, how can I derive the sound wave / air pressure over time, that would result from such a string?
I had considered simply summing up each segment's vertical (y) position at discrete time steps, but this approach does not work for any sh... |
As far as I know Rutherford measured only the
$$I\propto\frac{1}{\sin(\theta/2)^4}$$
intensity dependence, which we would expect for isolated gold atoms. Why didn't he measure Bragg scattering at the gold crystal?
|
It's often said that in classical physics a electron-proton system is not stable due to "Bremsstrahlung" and that one instead has to look at it quantum mechanically.
This doesn't make sense to me. The quantum mechanical Hamiltonian doesn't account for "Bremsstrahlung" either. Is this taken care of only in QED?
|
There is a beautiful demonstration, available in the text Robert S. Elliot, Antenna theory and Design, Wiley-IEEE Press, page 17 (Stratton-Chu solution), which shows how the electromagnetic field at each point $ \mathbf { r} $ of a volume $ V $, with boundary $S_1, ..., S_N $:
can be found from the following integral... |
I watched a video in which liquid oxygen when passed through the poles of the magnet gets suspended or rather sticks to it. It says it is due to diamagnetic nature of oxygen but in this way I think liquid nitrogen should repel from it as it is paramagnetic. But it went through without showing specific repulsion. Why i... |
Suppose I have some conserved charge in a 2 dimensional CFT
$$Q(|z|)=\int_{w=|z|}\text{d}w\,T(w).\tag{1}$$
The infinitesimal transformation induced on a field $\phi$ at $z$ is then
$$[Q(|z|),\phi(z)]=\int_{w=|z|}[T(w),\phi(z)].\tag{2}$$
Books in CFT claim this is not a well defined quantity. On the one hand this seems ... |
When adding two spin-1/2 particles, it is well known that the basis of the composite system can be written in terms of the spin singlet and triplet states. These sates have a well defined symmetry under particle exchange: the singlet is fully antisymmetric, while the triplet is fully symmetric. The same idea can be gen... |
The two images below are from different books. One has the $\hbar$ in the root below which seems right to me as that gets the dimensions correct but other does not have a $\hbar$. I am confused as to which is correct and why the second book has omitted the $\hbar$ (Not the one appearing in the exponent but the one ou... |
I've known about the existence of magnetic bubbles at Solar System's edge from a video edited by NASA from an official channel of YouTube, I refer [1] (as explicitly stated in the title, it was a probe that discovered it). On the other hand I know from an informative point of view that stars are classified according di... |
Good day,
I am a beginner in electrical engineering.I was wondering when the positive charge is passing through the circuit isn’t it constantly losing electrical potential energy as it is flowing from positive to negative point? Then shouldn’t we get a voltage when we put a voltmeter at point A and B in a circuit sinc... |
I was given a probability density $$ \frac{dP}{d\Omega} $$ where $\Omega$ is the solid angle such that $$ d\Omega = \sin \theta \ d\theta \ d\phi $$ and $\theta$ and $\phi$ the sperical coordinates angles. To obtain the probability we calculate the integral $$ P = \int \frac{dP}{d\Omega} \ d\Omega = \int \frac{dP}{d\Om... |
As elucidated by E.T. Jaynes in his seminal papers, there is a deep connection between information theory and statistical mechanics.
The nature of my question is somewhat soft, so I apologise for that. Anyway, does anyone know of any applications of spin model theory, integrability, and/or phase transitions (or in gene... |
Hill's sphere is the assumed sphere that a smaller body -rotating around a bigger one- attracts other objects to rotate around it.
For example, in the case of Earth, the radius of its Hill's sphere is about $1.5$ million km. That means every smaller object in this distance from Earth will rotate it. The Moon is in $384... |
Reading some papers about neutron stars, I found that some astronomers measured the frequency of a pulsar, which is a sort of lighthouse. My question is if the measured pulsar frequency is the same as the frequency of rotation of the associated neutron star.
|
In the follow Planck units have been used.
The Electromagnetic Energy-Momentum Tensor is $T^{\mu\nu} = \frac{1}{4 \pi} \left[ F^{\mu \alpha}F^\nu{}_{\alpha} - \frac{1}{4} g^{\mu\nu}F_{\alpha\beta} F^{\alpha\beta}\right]$ where $F^{\mu \nu}$ denotes the Faraday Tensor.
From the second Bianchi identity we know that th... |
The paper arXiv:hep-th/9308043 proves that the partition function of an arbitrary (unitary) two-dimensional topological theory is given by
$$
Z(\lambda)=\sum_{i=1}^n\lambda_i^{g-1}\tag1
$$
where $g$ is the genus of the surface, and $\{\lambda_i\}$ are some non-negative real numbers characterizing the topological order.... |
If one creates an oscillating electric field and a magnetic field, transversal to each other, and oscillating at a given frequency belonging to the visible spectrum, and moving in a given direction of an observator, will an observer see the same as compared to the same experiment where he looks at the light ?
Said diff... |
I would like to resolve a dilemma of squeezing or unsqueezing a bottle of beer/soda in order to keep the beer/soda for as long as it is possible from going flat.
I would like to ask 3 questions that should resolve it. I expect from the answers to these questions these outcomes:
Q1: To see if squeezing is a good practic... |
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