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I got confused about the true origin of spinors with regards to their connection to the proper orthochronous Lorentz group $SO^+(3,1)$. In the book on QFT by Maggiore that I'm following, we reached the Lie algebra corresponding to $SO^+(3,1)$ and then showed how it's isomorphic to $su(2)\oplus su(2)$*. Then it was simp... |
When we consider the interference of light through a thin film of water or a glass slab, light gets reflected at both air-water and water-glass interface. Correspondingly, there is an extra phase difference of pi due to reflection at the denser medium for both rays . So the path difference for 1st ray should be $\lambd... |
A spin-N field goes back to its original state after a rotation of $360^\circ/N$.
So a spin-1 field takes $360^\circ$, a spin-1/2 field takes $720^\circ$ and a spin-2 field takes $180^\circ$.
But this breaks down for scalar fields (called spin-0 fields). As it seems to suggest you must rotate it infinity times to get b... |
I have read about conducting charged shells and spheres and know somewhat about the electric fields associated with them. But I have never found anything on non-conducting shells. I have searched online and gone through several famous physics and electrodynamics/electrostatic books. Hence I have devised a thought expe... |
Well, one of the "mantras" of General Relativity is:
Einstein Field Equations concerns about the local geometrical structure of spacetime (the metric tensor) and tell you nothing about the fixed undelying topology of spacetime.
One way to study this fact is in the realm of Spherically Symmetric Wormholes. Specificall... |
I was looking at a straight forward answer on internet which I am unable to find.
Can there be a strong interaction in which transformation of one quark flavour into other takes place(Eg. up quark -> down quark)?
Can there be a weak interaction in which transformation of quark flavors doesn't take place?
If both the a... |
Quazars send baryons from other galaxies towards us which are deflected from by the local magnetosphere. The early solar system probably picked up many millions of extragalactic cosmic rays for every tonne of local atoms. Humans probably contain some baryons which are sourced from >3 billion light years away.
What happ... |
This might seem like a stupid question but please bear with me.
I've always studied and read that the molecules at the surface have higher energy than those at the interior and the explanation is also justified since very less energy is required to break them apart on surface so they must be at high energy. The molecul... |
I wound two coils (A & B) using 27 AWG winding wire. Each coil was wound on a ¾ inch thick x 3 inch steel rod. Coil A had 7000 windings. Coil B had 4600 windings. Coil A measured 128 ohms. Coil B measured 76 ohms. I connected a 6 volt lantern battery to each coil thinking coil A would produce a much stronger magnetic c... |
In particle physics the groups $SU(n)$ and its representations are more important than the groups $U(n)$. Is it only because these groups happen to give a theory that agrees with experiments, or is there some fundamental reason for the unit determinant condition to be important? I know $U(1)$ appears in electrodynamics... |
Consider the experimental setup for Young's Double Slit Experiment:
Here there is an angle between the directions of propagation of waves ,i.e., $\angle S_1PS_2$ - the angle between the electric and magnetic field vectors at that point other than the phase difference.
My question is:
Why is this angle never taken into... |
From Boyle's Law, in very low pressure ($P \rightarrow 0$), it is a good approximation for real gases to behave as ideal gases. (refer to the graph)
Boyle's Law stated that $ P \propto \frac{1}{V} $
So I am thinking that when $P \rightarrow 0$, $V \rightarrow \infty$, then by $\mathrm{density} = m / V $, supposedly d... |
I have been using Jefimenko's Equations for determining the electric and magnetic fields of a conductive coil with a (possibly changing) current. For most situations of interest this can be done to sufficient accuracy by approximating the wire as having zero radius and neglecting retardation. However, now I am investig... |
I know that far away from a distribution of charges, the fields can be approximated using Gauss' Law, and the fields become very similar to that of a point charge. Is there an analog for this in magnetics?
For example, how would this work for a loop of current, could it be approximated as a "point magnet"? That doesn't... |
I want to simulate a CoilGun system in python.
Assume The system circuit as a simple RLC circuit
It is the method that I used :
I used FEMM software to get force & inductance data at different slug distances from coil center.
Then I write the program this way :
let t= 0, z = 0, v=0, current = 0, timestep=0.000001
Loo... |
From internet resources, $α$ particles can only travel few distance in air (or few range in air), is that because it been absorbed in air?
|
The Time-dependent Schrödinger equation is given by
$$i\hbar \frac{d}{dt}|\Psi(t)\rangle=\hat{H}|\Psi(t)\rangle $$
From Classical Mechanics, we know that
$$\mathcal{L}=\dot{q}p-H$$
which should change in quantum mechanics as
$$\hat{\mathcal{L}}=\frac{1}{2}(\hat{\dot{q}}\hat{p}+\hat{p}\hat{\dot{q}})-\hat{H}$$
The questi... |
I'm doing some calculations on the motion of a rigid body as part of a project, and (as a tangent) I've come across something that I can't quite explain.
Case 1: If I apply a force $F$ though the centre of mass of a rigid body, I can make it move in a straight line with some velocity.
Case 2: If, however, I apply the s... |
What will be the waveform in the secondary coil of the transformer if the input is a sine wave of some frequency and constant voltage. Will there be any change in the waveform or will it remain same?
|
The Lindblad Master Equation is a generalization of the Schrodinger Equation for open quantum systems, given by
$$
\frac{\mathrm{d} \rho}{\mathrm{d}t} = -i \left[ H, \rho\right] + \sum_k \gamma_k \left( L_k \rho L_k^\dagger - \frac{1}{2} \left\{ L_k^\dagger L_k, \rho \right\}\right) = \mathcal{L}(\rho)
$$
where $\rho$ ... |
if I use a triangulation sensor and put a perferctly flat mirror in front of it (45°), will the measured distance be the same as without a mirror?
|
The spring force limits the degrees of freedom of a body connected to it, which fits the definition of a constraint force, but the work done by it is not zero. So what do we classify it as?
|
This question is a follow up to this question. Here my doubt is about a shell made up entirely of charges. I am asking this question because all physics and electrostatics/electrodynamics books talk only about conducting shells and spheres. Only a few contain details about a sphere made of charges. There are no details... |
In linearized gravity, the metric is given by the Minkowski metric and a small perturbation,
\begin{equation}
g^{\mu\nu} = \eta^{\mu\nu}+h^{\mu\nu},\quad |h^{\mu\nu}|\ll 1.
\end{equation}
Plugging this expression into the expression for our Christoffel symbols, we obtain
\begin{equation}
\Gamma^{\alpha}_{\mu\nu} = \fra... |
I am working on an electronics project in which I dispense melted wax at around 70 degrees through a syringe and metal veterinary needle as shown below. The syringe is heated via an aluminium block with embedded heater cartridge. The block sits around the syringe body tightly. The problem I am having is that everything... |
Lagrangian for a particle moving under influence of conservative force given by
$$\mathcal{L}=T-V$$
that is Kinetic energy minus Potential energy. Now for a system of particles I expect the same form of lagrangian. But Consider a rigid body with say $n$ particles. In this case I need to take care of constraints too. We... |
Lets say i have a model rocket that is propelled by Liquid Rocket Engine.(This speculation is according to my knowledge ......that could be wrong ) The engine provides a thrust of 300N and has an apogee at 15000m above surface and is currently at apogee. Its mass is about 10 kg at launch but it has burnt 40 kg fuel and... |
If I was to touch a charged object, I may get an electric shock due to the potential difference between myself and the tap and because I am earthed. If I was not earthed, the electric shock would not occur.
When I get out of my car, I can become charged because of the friction between myself and the car seat. Then when... |
I know that observed phenonmenon like gravitational redshift, gravitational time dilation and bending of light rays tell us that special relativity is invalid in the presence of gravity.
However, are there any experiments that show us special relativity is valid in the absence of gravity? I would naively think that exp... |
Dirac Lagrangian density is is
$L= \bar{\psi}(i\gamma_{\mu}\partial^{\mu}-m)\psi$.
Here $L$ is a number. $\psi$ is a $4\times 1$ matrix. Now to get momentum conjugate to $\psi$, we define $\pi=\frac{\partial{L}}{\partial{\dot \psi}}$.
This kind of procedure we follow before promoting $\psi$ and $\pi$ to operators. I.e... |
If the accretion disk is on the (x,y) plane of an orthogonal reference frame what happens to objects outside the (x,y) plane (e.g. objects on the z-axis) ? In other words why is the accretion disk a disk and not a sphere (as space in 3D).
Thank you.
Twelvetones
|
If cells are connected in series with positive terminal of one cell with negative terminal of other cell what is the potential difference between those two terminals..? Is that not zero.?
|
In the following, we assume that the polarization is aligned such that the scalar treatment of the electric field is justified.
Furthermore, we limit the discussion to a fixed coordinate $x=0$ to drop the wave vector dependency.
Classical description
Let's consider a classical electric field
$$
E(t)=A(t)\cos\omega_c t
... |
Please suggest beginner-level textbooks or lecture notes on the quantum aspects of black holes. I mean Hawking radiation, Blackhole evaporation, entanglement, etc without knowing string theory. I am not familiar with string theory at all at a technical level. I want to learn things leisurely in baby steps.
|
Classical mechanics is famous for its supposed ability to theoretically calculate the state of a system at any given time provided all the necessary initial conditions. I believe this is the definition of determinism.
But a simple system if 3 particles interacting gravitationally fails to admit such a description.
Some... |
Musing about the historical evolution of the notation for the gravitational constant ($f$, $G$, $\kappa$, $\kappa^2$), I found myself digging for the first time in my life into Newton's Principia, looking for the data he could have used (had he thought algebrically) to estimate his constant (see Did Newton estimate the... |
I am looking at the following formula and trying to understand why the following integration of the electron energy $E_e$ is the total number of electrons:
$\int d^3pf(E_e,T) = N_{e} V$
where $N_e$ is the electron energy density and V is the volume. Therefore $N_{e} V$ is the just the total number of electrons.
I integ... |
https://en.wikipedia.org/wiki/Magnifying_glass
As we see the magnifying glass is a circle.
Can we design & construct magnifying glass with other shapes viz triangle, rectangle, hexagon, Kite ?
Will it effect the magnification of the object which we observe with the magnifying glass after changing the circular shape to ... |
I conjured up a scenario where there are two rods free to rotate about a hinge connected by their ends by spring of spring constant $k$,both their masses are $m$ and length $l$ and mass is uniformly distributed throught the length, now on the upper rod a charge $q$ is uniformly distributed and a constant horizontal e... |
Looking around thru space we see a variety of colors. If colors are simply electromagnetic waves and waves are just forces then why don't these electromagnetic waves of each colors cancel or add up to each other and why can we still distinguish individually among the electromagnetic waves of each color and produce a di... |
It is said that a magnetic moment is always associated with angular momentum. For a particle, the magnetic moment $\boldsymbol{\mu}$ and angular momentum $\boldsymbol{l}$ are related by
$\boldsymbol{\mu}=\gamma \:\boldsymbol{l}$
where $\gamma$ is the gyromagnetic ratio. In the Einstein-de Haas experiment, the rotation ... |
How to make sense of change in static block universe if every event already exist in block? if you say it's an illusion created by brain even that requires forward evolution of patterns of information in our brains,so what constitutes this change? If everything is just what it is in block and past, present and future e... |
I came across the following question in one of my reference materials:
Method 1: I found the radius of curvature of the trajectory (for options B, C and D) by using the equation a=v^2/r, and I got options B and C as correct, which is the answer given.
Method 2: I tried drawing a diagram using the instantaneous axis of... |
In quantum Brownian motion, bosonic/harmonic oscillator bath and interaction described by Hamiltonian
$$
H_B = \sum_{n}\hbar\omega_n(b_n^\dagger b_n) \\
H_I = -\sigma_x \otimes B
$$
and
$$ B = \sum_n \kappa_n\sqrt{\frac{\hbar}{2m_n\omega_n}}(b_n+b_n^\dagger)$$
We have two correlation function to describe time evolution... |
I was studying laws of friction. Wikipedia says there are three laws based on Coulomb's model of friction.
However, most of the other websites say there are five laws, stating
When an object is moving, the friction is proportional and perpendicular to the normal force.
Friction is independent of the area of conta... |
Consider spinning a closed chain as in the figure above, I want the speed at which the chain will be kept in a horizontal plane. Inspired by this irodov question
Considering taking the point where the chain and rope are pivoted, if we compute torque around there on all mass elements then we can say:
$$ I_{net} \alpha ... |
I am currently studying electricity in my physics class, and am really confused about electric potential in a uniform electric field, like the one pictured.
What I don't understand is, how come many textbooks say that the electric potential at the negative plate is zero. The equation for electric potential is $V=kq/r$... |
I see many answers to what happens to 'an observer' or 'matter' or 'clocks' passing the event horizon of a black hole, but would like to ask how the structure of solid or liquid matter is affected?
For example imagine I push a diamond prism through the event horizon (this is a simple, single element, regular crystallin... |
This is a problem from my introductory physics textbook:
A wheel of moment of inertia $I$ and radius $r$ is free to rotate about its centre. A string is wrapped over its rim and a block of mass m is attached to the free end of the string. The system is released from rest. Find the speed of the block as it descends thr... |
I am not sure if my simplification works in this problem:
Problem:
I have a beam which is strap around with cargo straps. First picture presents section through second picture. So applying Newtons second law:
$$F=G=\frac{m_{beam} g}{2} $$
so the F is the force in the cargo straps. Therefore I can calculate which king o... |
Suppose we have an observer $O$ in free fall and electric charge $e$ on the surface of the earth. As $O$ is in inertial frame, Maxwell's equations are valid for $O$. However, according to general relativity the electric charge $e$ is accelerated. Does the observer $O$ see radiation emitted by the charge $e$? Has any e... |
Calculating light speed given a simple index of refraction is trivial, of course ($n = \frac{c}{v}$).
I'm not sure, however, how one would calculate the 'time of flight' for a light signal in a medium where the index of refraction is 'more complex'. Take ice, for example (which I'm working with here), whose refractive ... |
I have a software issue I am trying to tackle.
I need to calculate the joules done by pedaling a bycicle one full rotation of the pedals. The way that I am currently doing is this:
F - I have force sensors on the two bicycle pedals that tell me how much force the foot is pushing the pedal. So in one rotation I might... |
The exercise I'm trying to solve reads as follows:
A series $RC$ circuit is driven by $v_{s}(t)= 25u(t)\: V$. Given that $i(0)=2 \:mA$, $v_c(0)=4\:V$, and $v_c=10\: V$ at $t=80\:ms$, determine the values of $R$ and $C$
I'm trying to guess that there should be another voltage source, because from the equation that the... |
Most of us have noticed that Fidget Spinners or celling fans or any kind of round shaped rotating objects (including, perhaps, bicycle rims) create a perception of them moving in an opposite direction to that of the applied force. When the speed becomes faster than what it was in the beginning, it looks as if it become... |
I've heard tell that many galaxies have visible mass profiles which do not match up to a predicted Gravitationally Newtonian velocity distribution. Can anyone here find me an accessible paper of an extremely articulate measurement of the mass of a specific galaxy with a numerically predicted velocity profile compared t... |
To begin with, I'm clearly not a physicist but I'm certainly interested by several physics questioning.
So, my question here is, according to Einstein's relativity, I understood that travelling at the speed of light would be instantaneous due to space and time dilation. Then, from the point of view of a photon that goe... |
I initially coded my simulation using the standard equations of motions, but as is known, it ended up being quite unstable, even if it technically worked.
If we take x(t) to be the position-function of the equations of motion, I calculated my "next" position in the simulation by re-factoring x(t+delta), as follows:
x(t... |
I was thinking of a problem that most of the lecture notes go over when introducing special relativity to the students.
Consider a spaceship with Alice inside it. Let's say the spaceship is traveling at a speed of $0.7c$. Alice then shines a laser light and tries to calculate the time taken by the light to hit the othe... |
For a closed system composed of two subsystems in a pure, non-entangled state, what mathematical property must the Hamiltonian have for the system to evolve to an entangled state?
What property must it fulfill for the system to evolve into a mixed state?
Could you give some examples of both cases?
|
Im solving porblem 1.6 the book of many particle physics of mahan where i need to find the eigenvalues of the tight binding hamiltonian, for the nearest neighbours
\begin{equation}
w\sum_{i \delta}\left( a_{i}^{\dagger} b_{i+\delta}+ b_{i+\delta}^{\dagger}a_{i}\right)+\sum_{i}\left(A a^{\dagger}_{i}a_{i}+Bb^{\dagger}_{... |
Related to my previous question.
When two colliding objects are at rest, say, a book on a table, the normal force the table exerts on the book will exactly cancel out the force of gravity (or other forces) the book exerts on the table. Due to that, I've been subconsciously assuming that these forces are present in that... |
To make a general diffeomorphism I can make an infinitessimal transformation to the coordiante $x^\mu$ to $x^\mu + \delta f^\mu(x)$.
Now I want to restrict it so I only allow transformations such that:
$$\partial_\mu f^\nu(x) + \partial_\nu f^\mu(x) = 0$$
This is because a certain identity I was working on only works i... |
I'm going over Rovelli's Covariant Loop Quantum Gravity notes http://www.cpt.univ-mrs.fr/~rovelli/IntroductionLQG.pdf and in section 2.4.2 "Boundary formalism" he briefly develops how to think about quantum fields in the boundary formalism. However, I noted that he restricts his discussions to "finite" bulks of spacet... |
This is follow up question for
If two event horizons approach each other, can I observe the collision?. According to the answer by Chiral Anomaly, we can see the merging event horizon, such that.
What if I locate a single atom at the exact center location, what is going to happen?
|
I’m studying QFT and confused about the difference between $D^{(s_{+},s_{-})}(\Lambda)$ and $D^{(s_{-},s_{+})}(\Lambda)$.
For example, when we make the vector representation, we don’t take $D^{(\frac{3}{2},0)}(\Lambda)$ but $D^{(\frac{1}{2},\frac{1}{2})}(\Lambda)$. This is because (1) $D^{(\frac{3}{2},0)}(\Lambda)$ is ... |
Intuitively, quantizing a field implies that there exists a probability for each state of the field denoted as
$$\Omega[\psi]$$
So the vector $|\Omega\rangle$ must be a superposition of all possible field states weight with an amount relating to probability
$$|\Omega\rangle=\Omega[\psi_0]|\psi_0\rangle + \Omega[\psi_0+... |
How does Wick rotation work with magnetic fields?
Let us take up single-particle $d$+1 QM. Then the Euclidean time path integral is given (in $\natural$ units) by $$ \langle x| \exp(-t H) y\rangle = \mathcal{N} \int_{\gamma:[0,t]\to\mathbb{R}^d:\gamma(0)=x\land\gamma(t)=y}\exp(-\int_0^t\|\dot{\gamma}\|^2+V\circ \gamma)... |
I'm working with an antiferromagnetic spin model on a bipartite lattice, which I am trying to analyze via Holstein-Primakoff spin-wave theory. Because the theory has two sublattices, there are naturally two boson flavors $a,b$. In Fourier space, I've found an exact form for the Hamiltonian in terms of the bosons:
$$\su... |
Tonight I observed a phenomenon that I saw that before thousands of times.
I saw Steam on the glass of the window, and I wondered when this happens, what change happens to heat transfer? is it makes it possible to cold weather can more easily transfer from outside to the room?
I would appreciate in advance for your ans... |
If I define coherent states of the 1-d SHO to be eigenstates of the lowering operator, I know that these states minimize uncertainty.
I know the computations, but I was wondering if there was some deeper reason why lowering eigenstates necessarily minimize the uncertainty. Is there any such good reason or is this just ... |
I am trying to understand how to conserve angular momentum in a elementary decay/reaction.
Consider the elementary reaction:
$$
K^{-}(J = 0) +p(J = 1/2) ~\to~ \Omega^{-}(J = 3/2) + K^{+}(J = 0) + K^{0}(J=0)
$$
We can see that net angular momentum is increased by one unit.
So as per angular momentum conservation law th... |
Merging black holes undergo a phenomenon called "ring-down" after the merger. If a black hole were to be perturbed by a hypothetical gravitational wave, would it exhibit a resonance type phenomenon that depends on the frequency? If so, how would that frequency be related to the black hole mass?
|
I can't seem to figure out how my teacher got to this. This is the circuit I am supposed to calculate resistance for (my teachers calculations are at the bottom of the picture):
When I try to calculate the resistance, I basically just use the two rules for parallel and series.
First I add up the resistance from the re... |
The question concerns the topology and dimensions of Helium 3A and 3B
A. The Helium 3A phase shows the same low energy excitations as those of a 2 spatial dimensional chiral p-wave superconductor --- with the half-quantum vortex in a chiral p-wave superconductor of spinful fermions (as the order parameter of A phase of... |
I have been reading the derivation of Lorentz transformations in the appendix of relativity:the special and general theory by Einstein and am stuck in the following spot:
He states
$$
x - c t = 0\tag{1}
$$
implies
$$
x' - c t' = 0\tag{2}
$$
and this implies
$$
x - c t = k (x' - c t')\tag{3}
$$
where $k$ is a constant. ... |
In the electromagnetic interaction a photon is exchanged which can cause a repulsive force between to charged particles
like the electron/electron or up/up quarks interactions. But when i look at the Feynman diagram two opposite sign charges
the attractive force is also mediated by the photon. This is strange as a tran... |
You (with a mass of 75 kg) are standing at the edge of a stationary merry-go-round that has a mass of 900 kg and a radius of 4 m. You can assume that the merry-go-round is well approximated as a circular disc, with I = (1/2)MR^2. To get the merry-go-round spinning, you throw a 2 kg rock in the horizontal direction that... |
a) Consider a harmonic oscillator with Hamiltonian $H=(1/2)(p^2+q^2)$ show that any phase space trajectory $x(t)$ with energy $E$, on the average, spend equal time in all regions of the constant energy surface $Γ(E)$.
I have seen answers to this questions but I simply dont understand it. Is it possible to use Liouvil... |
When an electron transitions from an excited state to the metastable state, no radiation is emitted i.e. a radiationless transition.
My question is: Where does the energy difference between excited state and metastable state go?
|
The idea of "force-carrying particles" is insane to me. Because if I hold two magnets near each other, probably zillionths of photons are constantly being exchanged bwteen them. In extreme form, two stationary electrons can be the source of infinite photons exchange. Or protons in nucloes must constantly exchange gluon... |
The time-axis and the space-axis overlap for a photon's world line. Does it mean that photon has no "past" or "future" but only "present" and no "there" but only "here"? I mean how does the photon observe the world?
|
If a body (eg a metal) is glowing red hot then its temperature can be approximated solely based on the colour. But what if that colour is not due to blackbody radiation but due to excitation of electrons? Would temperature still be the same?
|
Needless to say, I’m lost, and admittedly a touch angry. Why the heck do we even allow non-normalizable wave functions? Yes, I completely understand why and how plane wave solutions to the free-space Schrödinger equation cannot be normalized, but what I don’t understand is on what grounds we somehow just forget about t... |
In finding the eigenfunctions, $\psi_E$'s, of the free-particle Hamiltonian in 1d,
$$
H = -\frac{\hbar^2}{2m}\frac{d^2}{dx^2},
$$
with eigenvalues $E$'s, subject to the conditions that they are bounded, one finds that corresponding to each energy $E>0$, there are two orthonormal eigenfunctions given by $\psi_{E, +}(x)=... |
I often read from textbooks that in relativity, space and time are treated on an equal
footing. What do authors mean when they say this?
Are there any examples that show space and time are treated on an equal footing? Conversely, what examples show that space and time are not treated on an equal footing?
|
I recently read an article that disputes relativity using Newton's cradle. It basically says that if you have one ball coming at velecity V with the kinetic energy of one ball, it cannot modeled as the other four balls moving the other way at -V, because then the initial kinetic energy is that of four balls moving, whi... |
Forgive me if this is dumb.
I connect the bicycle pump tube through a hole in a water bottle cap (half-filled with water) and place it in the water and then completely seal the setup. Then I press down the handle until the pressure builds and air bubbles in. Finally I will remove the pump carefully, not releasing press... |
https://www.magformers.com/
They are magnetic shapes.
The corners of shapes where the magnetic material is seem to be attracted to both North and South (I have tested them on bar magnets) and yet they attract other magformers and ferromagnetic materials so please explain how they are magnetically structured?
|
Suppose that an object O is in glass ($ \mu $ = 1.5), 6.5 cm from a spherical glass-air interface (from P in Figure 1) where glass is on the concave side and air is on the convex side. In the diagram of this situation in Figure 1, glass lies to the left of the interface while the air lies to the right (of the interface... |
Why is the electric field caused by the induced surface charges in the dielectric less than the electric field caused by the conductor plates in a capacitor?
|
Suppose a particle's time evolution in a 2D $k$-space of first Brillouin zone is as shown in the figure. How can we interpret the motion of the particle in $x$-space?
Any hint for interpretation is useful for me.
|
We always tend to think that future will come no matter how far in the future that is. But according to some theories, time started at the big bang and the term "before the big bang" doesn't make any sense just like going to north does not make any sense when you are at the north pole. But there is also the south pole ... |
I have got stuck in these concepts for a fews days: Wick rotation, Euclidean spacetime and QED in gravity.
Generally, in Minkowski space time, there is a factor $i$ in front of the action $S$, e.g., the path integral looks like
\begin{equation}
\int \mathcal{D}{(\mbox{fields})} \exp\{iS_{Mink}\}
\end{equation}
Now we p... |
If we have two cubic cavities both with perfectly reflecting walls, one much large than the other, both with a blackbody in them, then when they are both in thermal equilibrium with their surroundings and are at the same temperature the much larger box will permit a range of frequencies that the smaller one won't.
Then... |
The question is if modern particle accelerators (or cosmic rays for that matter) can create black holes. Has those events been detected? If not, how far are we in terms of orders of magnitude energy?
Bonus question: is creating black holes scientifically interesting?
I've read this question, but the accepted answer is ... |
I'm considering a Hamiltonian consisting of Pauli spin matrices, $\sigma^i$ in a 1+1D system with of one spatial and one temporal dimension, $(t, x)$. Suppose I then make a transformation
\begin{align*}
x^\mu \rightarrow x'^\mu = \Lambda^\mu {}_\nu x^\nu
\end{align*}
I want to determine how my Hamiltonian transform in ... |
I am currently reading about the Bulk photovoltaic effect in Weyl semi-metal. Shift current is one of the major sources of current in the Bulk Photovoltaic effect. They originate in non-centrosymmetric materials. They don't need an applied field for charge separation when illuminated by a light source, whereas conventi... |
The LIGO interferometers are 2 dimensional, they have $4\rm\ km$ legs that are perpendicular to each other. Could a 3rd $4\rm\ km$ leg either with a straight up tower or deep into the earth, provide directional information about the source when gravitational waves occur?
I know a $4\rm\ km$ tower or hole isn't really ... |
Standard filters in electronic circuits are devices that allow a certain range of frequencies to pass through while attenuate other frequencies. I was wondering if something similar could be built that allowed frequencies to pass through if their amplitude was above a certain threshold.
Detail: Say there are four signa... |
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