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In a theory containing gauge fields or higher-form gauge fields, if the background spacetime is a complicated manifold, a nice way to represent the configuration of the gauge field mathematically is with a vector bundle. Often, important aspects of the configuration are captured in the cohomologies of the vector bundle... |
What is the general form of the Pauli matrices for a $3\times 3$ matrix (spin $s=1$)? Do these generalized Pauli matrices satisfy all the properties exhibited by the Pauli $2\times 2$ matrices, such as being Hermitian? Furthermore, is it possible to represent all Hermitian $3\times 3$ matrices using these generalized ... |
Assume a rocket is being vertically accelerated in a homogeneous gravitational field.
In the reference frame of the rocket, the burnt fuel is being exhausted downwards with a velocity of $\Delta u$.
We ignore air resistance.
In a small time interval $dt$, the rocket loses the mass $dm$.
So the momentum of the rocket in... |
The (time-independent) Schrödinger equation is for sure the most important equation in quantum mechanics:
$$-\frac{\hbar^2}{2m}\nabla^{2}\psi(\vec{r}\,)+V(\vec{r}\,)\psi(\vec{r}\,)=E\,\psi(\vec{r}\,).$$
Let’s consider the one-dimensional equation,
$$\frac{d^2\psi(x)}{dx^{2}}-\frac{2m}{\hbar^2}\left[V(x)-E\,\right]\psi(... |
I read a paper about using femtosecond laser to process an atom. The units used in the paper bothered me. I have four questions.
(1) Why the unit of energy is cm$^{-1}$?
(2) It seems that the author take the reduced Planck constant to be one. Then what is the meaning of $\omega$? Is it frequency or angular velocity? W... |
I’ve been told that the fact that quantum systems tend to become more entangled over time shows how statistical mechanics can arise from quantum mechanics, but how exactly does this work?
Is it just the idea of particles being equally likely to be in any of the microstates or is there something more fundamental?
|
The question that I don't even know where to start on is as follows:
Utilizing the fact that any wave can be considered as a superposition of plane waves, show that in the absence of a field, the matter wave $\psi(\mathbf r_2,t_2)$ at the point $\mathbf r_2$ at the instant $t_2$ can be deduced from the values $\psi(\ma... |
(Please excuse my English)
One day, I realized that I had not clearly learned about the relation between the energy and the momentum, though I am an educated engineer.
I just thought the energy is a kind of scalar transform of the momentum, in Newtonian mechanics. Also I thought the energy conservation can be derived f... |
What is different between the lost of coupling and efficiency overall coupling ?
I know both of them (power out/power in)e.g (5%) that means is 5% light transmission and 95% lost.
|
I have the action
$$S=\int d^4x\sqrt{-g} \Big[\frac{1}{8}\phi^2R- \frac{1}{2}g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi - \frac{1}{2}m^2\phi^2\Big]$$
where $\phi$ is a scalar field and $R$ is the scalar curvature (signature $-+++$)
I want to get the equations of motion and then substitute in the FRW metric.
Could someo... |
Straight to the point: what's the result of the commutator of the magnitude of the position and the momentum operators and how can I approach it, i.e., $[|\mathbf{\hat{x}}|,|\mathbf{\hat{p}}|]=$ ?
My efforts: (1) trying to use $|\mathbf{\hat{x}}|=\sqrt{\sum \hat{x}_i\hat{x}_i}$ doesn't seem to help because of the squa... |
I am currently trying to self-teach special relativity (if relevant, I am still in school). I think that I already have a good intuitive understanding of, for example, time dilation and length contraction as a result of constant $c$.
I now want to understand (by which I mean, actually understand, not just learn!) how ... |
When reading Real-time terahertz imaging with a single-pixel detector a paragraph states:
"(...) these carriers will diffuse inside the semiconductor with a characteristic length around ~ 0.3 mm rendering the infinitely thin conductive layer approximation invalid."
I thought 0.3 mm would be a very thin layer, but appar... |
In the Jaynes-Cummings model (JCM) https://www.tandfonline.com/doi/abs/10.1080/09500349314551321, you have a model for a single cavity where you have two bosonic state operators coupled to a photon operator which describes the radiation that happens when the bosonic fields go from the excited state to the ground state.... |
Let's say there is a cube in deep space. There is no light or force being applied to the cube. Is it possible to know if the cube exists in this scenario?
Sorry if the question seems too simplistic. I was just curious if scientists had non-invasive ways of knowing an object exists.
|
Let's say we have a grounded conducting plane at $z=0$ and a charge moving above it with some position $\vec{r}_q(t)$ and velocity $\vec{v}_q(t)$. I know that in the particular case when the velocity is just zero the potential is
\begin{equation}
\phi(\vec{r})=\frac{q}{\sqrt{(x-x_q)^2+(y-y_q)^2+(z-z_q)^2}}-\frac{q}{\sq... |
In making wafers for chips, when using masks and demagnifying to a smaller size, is there any limit to demagnification? For light, a microscope’s numerical aperture and wavelength limitation prevents the level of magnification from becoming higher than a certain level.
|
Given $A \otimes B$ is Hermitian, does it follow that $A$ and $B$ are necessarily Hermitian?
I've only gotten as far as $(A \otimes B)^\dagger = A^\dagger \otimes B^\dagger = A \otimes B$ and I haven't been able to prove that $A = A^\dagger$ and $B = B^\dagger$.
|
There are two forces we know, Centripetal force (or Gravity) and Centrifugal force. Both are applied to all the planets including earth. Planets are kind of spherical due to gravitational force but also not perfectly round due to this centrifugal force (or any other force idk) applied.
I read a lil before asking this q... |
If I'm using electricity not to induce steady-state current, but instead to force as much charge as possible into a given material, given I know the relevant properties of the material, how do I calculate how much voltage and/or time I need to put a given charge on the material?
Assume that the circuit is open, in that... |
My question is related to a statement:
If a pendulum is experiencing free fall, then it will not oscillate.
The statement is true in the sense that its acceleration is (approaching to) zero, then according to the period equation $T$ would be infinity.
I think this sense comes from General Relativity. However, I'm not... |
I want to calculate the flow rate of water through holes in a mesh.
In the following hypothetical situation water is flowing through a 13mm diameter pipe at a velocity of 3 meters per second and a pressure of 0.55 mega pascals. (I do not know the water temperature or the surface roughness of the interior of the pipe, o... |
Coulomb's law for the static electric field of a point charge is given by
$$\overrightarrow{E}=\frac{1}{4\pi\epsilon_0}\frac{q}{r^2}\hat{r}$$
Now if we take the divergence of both sides of the above equation we will get
$$\overrightarrow{\nabla}\cdot \overrightarrow{E}=\frac{q}{4\pi\epsilon_0}\left\{\frac{1}{r^2}\frac{... |
I'm a researcher at University Federal of Santa Catarina Brazil and I work with lasers.
I'm looking for information about how to calculate the Nominal Ocular Hazard Distance (NOHD) to a laser line and not to a laser point.
I have a laser line with 150 mW, thickness 1,14 mm with working distance 5m and fan angle 30°.
Li... |
I am having trouble understanding the steps taken in (11.27) equation in Quantum Field Theory and the Standard Model by M.D.Schwartz.
I don't understand how to get the middle diagonal matrix in the second last statement of the equation.
Here is my attempt. I am writing
$$ \begin{pmatrix} \sqrt{p \cdot \sigma} \xi_{s'} ... |
The uncertainty principle of Heisenberg says that the uncertainty in the position of a particle multiplied by the uncertainty of the momentum of a particle is always more than or equal to $\frac{\hbar}{2}$:
$$\Delta x \Delta p \ge \frac{\hbar}{2}$$
Rearranging, you get this:
$$\Delta p \ge \frac{\hbar}{2\Delta x},$$
wh... |
Torque = r x F = r*F*sin(theta) => So units will be kg*m^2/s^2
Torque = I*alpha => SI units is kg*m^2*rad/s^2
There is a rad unit extra in the second formula. They both should match right because they are calculating torque.
|
We can identify Minkowski space-time $M^4$, of metric signature $(1, -1, -1, -1)$, with the (real) space of $2 \times 2$ (complex) Hermitian matrices under the map $(v_0, v_1, v_2, v_3) \mapsto v_0 I + v_1 \sigma_x + v_2 \sigma_y + v_3 \sigma_z$ where $\sigma$'s are Pauli matrices.
Given a Hermitian matrix $X$ and some... |
GR and Newton give almost exactly the same result for the orbits of planets and the acceleration of falling bodies. Is it an incredible coincidence, or does GR have some tiny term (e.g., ict) that accounts for the difference? Is it possible to make GR collapse to Newton's law by ignoring that tiny term?
|
Does angle of minimum deviation depend on angle of prism?
I know that angle of deviation does but I don't feel like the particular behavior is relevant for the angle of deviation as well? Please help me clarify it
|
Supposed I have the following expression for the error in an arbitrary variable S:
$\frac{\delta S}{S}=\sqrt{(\frac{\delta q}{q})^2+(\frac{\delta w}{w})^2}$. What is wrong with concluding that $\frac{\delta q}{q}=\sqrt{(\frac{\delta S}{S})^2-(\frac{\delta w}{w})^2}$? I am uncertain about the fundamental origin of the p... |
I knew that I would get an Sinusoidal curve in the first derivative but what happens in the second derivative. Is there any specific quantity for this?
|
According to the book Quantum Information meets Quantum Matter, ordered phases can either be described by a Landau free energy: symmetry-breaking ordered phases; or there are different ways in which local Hamiltonians can give rise to global patterns: topological order.
Quasicrystals don't seem to be symmetry-breaking,... |
In the mathematical formulation of the Standard Model, which I do not understand yet, there is a capital letter $D$ or $D$-with-a-slash-through-it that I can't find an explanation for.
Flip Tanedo (a popular 'quantum blogger') just said offhand that it has something to do with bosonic gauge fields.
I am curious because... |
Consider a Rotation transformation on momentum state,
$$U^\dagger(R)\hat{\mathbf{p}}U(R)=R\hat{\mathbf{p}}$$
Now the question is whether,
$$U^\dagger(R)\hat{H}U(R)=\hat{H}\,?$$
Here, $\hat{H}$ is the Hamiltonian of a free particle. Is it always true? Is there any counter examples?
My attempt:
\begin{align}
U^\dagger(R)... |
How can I calculate the gravity or "$g$" of a video game displaying frames at $60\,\text{Hz}$, to $9.8\,\text{m/s}^2$?
Please let me know if you need any more parameters or details or if something is not clear!
|
The set up:
An intertial frame Y-X used to describes trajectory of an insect on some rigid body using some relative vectors. Symbols: $ \vec{r_a}$ is is the vector connecting the origin to some point on the rigid body, $ \vec{r_b} $ is the vector connecting origin to the insect and $ \vec{r } $ is the vector connecti... |
It is known the quark condensate $<\bar{\psi}^{i}_L\psi^j_R>=\sigma \delta^{ij}$($i,j$ are flavour indices ) breaks the symmetry group $SU(N_f)_L\times SU(N_f)_R$. Because it is only invariant under diagonal subgroup of $SU(N_f)_L\times SU(N_f)_R$. This kind of breaking is generally identified as spontaneous symmetry b... |
Objective:
Show that
$$
\int^{\infty}_{-\infty} x e^{-x^2} H_n(x) H_m(x) dx = \pi^{1/2} 2^{n-1} n! \delta_{m,n-1} + \pi^{1/2} 2^n (n+1)! \delta_{m,n+1}
$$
My attempt at this is:
\begin{eqnarray*}
\sum^\infty_{n=0} \frac{2^n s^n u^n}{n!} (s+u) \sqrt{\pi} &=& \sum^\infty_{m,n=0}\frac{s^m u^n}{m! n!} \int x H_m(x) H_n(x)... |
If we consider a spin in an external magnetic field, it starts to precess around the vector of the magnetic field. The same should be true for any angular momentum.
But what does this mean for the wavefunction of the electron? To be more precise: What happens to the wavefunction if we apply an external magnetic field? ... |
I know that the galaxy rotation curve doesn't obey general relativity and instead of decreasing, the star velocity remains constant which is shown by a flat rotation curve (rotation velocity v/s distance).
but I often see that the curve is flat till the graph ends but it doesn't show the distance till which the curve i... |
Using the Einstein-Hilbert action for a Universe with just the cosmological constant $\Lambda$:
$$S=\int\Big[\frac{R}{2}-\Lambda\Big]\sqrt{-g}\ d^4x$$
I would like to derive the equations of motion:
$$\Big(\frac{\dot a}{a}\Big)^2+\frac{k}{a^2}=\frac{\Lambda}{3}\tag{1}$$
$$2\frac{\ddot a}{a}+\Big(\frac{\dot a}{a}\Big)^2... |
My teacher has proved the following:
$$ \mathit v^2 = \mathbf v·\mathbf v = \frac{d\mathbf r}{dt}·\frac{d\mathbf r}{dt} = \left(\frac {ds}{dt}\right)^2 \Rightarrow \mathit v = \frac{ds}{dt} $$
Because $\mathit v$ is always positive and:
$$\Vert d \mathbf r \Vert =ds$$
If I do the same with acceleration I get this:
$$ \... |
Suppose two bodies collide inelastically, does the total loss in kinetic energy get converted into potential energy associated with the deformation? Or does the energy also transform into other forms like sound or light?
|
Assuming the electrons are non interacting and spin degenerate, the conductance of a quasi one dimensional quantum wire is quantised in units of $2\frac{e^2}{h}$. For small voltages, we simply count how many bands have their bottoms below the chemical potential and multiply this by $2\frac{e^2}{h}$. This is due to the ... |
It is a well-known fact that light from the Sun takes about 499 seconds to reach Earth. However, there is such a thing as time dilation; different observers experience time differently due to there existing between them either a relative velocity (or a difference in in gravitational potential) between their locations. ... |
I am reading the following article on bosonization :
https://arxiv.org/abs/cond-mat/9805275
and I encountered the following set of equalities.
$$\begin{align}
[\phi_\eta (x),\partial_{x'}\phi_{\eta'}(x')]&=\delta_{\eta\eta'}\frac{2\pi}{L}\left[\frac{1}{\exp\left(i\frac{2\pi}{L}(x-x'-ia)\right)-1}+\frac{1}{\exp\left(-i\... |
I (re-)learned about Bell tests from the ground up based on this very intuitive lecture by Spekkens. In a nutshell, realism is violated whenever measurement statistics cannot be reproduced by preexisting states. In algebraic terms, realism is a convex hull and any measurement statistics outside of that hull are essenti... |
I amd reading a proof Goldstone’s theorem in Zee's QFT book. On page $228$, Zee presents the proof as follows.
The conserved charge $Q$ is given by
\begin{equation}
Q=\int d^D\vec{x}J^0(t,\vec{x}).
\end{equation}
In the next, he gives a state ket $|s\rangle$ as
\begin{equation}
|s\rangle=\int d^D\vec{x}e^{-i\vec{k}\cdo... |
I just read some articles about binary BH merger simulation. These state that at a certain instant a common apparent horizon(or MOTS)
appears, surrounding the two BHs. This instant is called the bifurcation time.
My question is why is it a complete closed surface? In a configuration without spatial symmetries why canno... |
I recently encountered a question in a physics workbook, a car of mass m kg is lifted by two cranes to a height of h metres, the cranes lift the car in t1 and t2 seconds respectively (t1<t2), then which crane will consume more fuel.....If we consider work as the main parameter then both cranes consume the same fuel (th... |
When we talk about kinetic energy of a body, it is actually the combined kinetic energies of all the atoms in that body. Now suppose a body is at rest. So its atoms would have some internal random motion and thus we can measure its temperature. But suppose it starts moving with a constant velocity $v$, so it will have ... |
What are extended modes?
I came across this concept while reading about photonics and photonic crystal. But I am not sure what is an extended mode.
|
So I've been taught that the work-energy principle says that the total work done on an object is always equal to the change in kinetic energy of an object.
Now let's say that I have a car moving up an incline at constant speed. The kinetic energy does not change from point A to point B, but the potential energy does, r... |
I am trying to calculate the wavelength for the first spectral line in a Balmer-series for a two times ionized lithium, $\text{Li}^{2+}$.
I know that the atomic number $z$ is 3 for lithium and it is hydrogen-like since it has lost two of its electrons. I also know that the answer to this question is $72,88 \cdot 10^{-9... |
I'm studying Merzbacher's Quantum Mechanics. In Chapter 2 Section 1, he "derives" the expression $\psi(x, t)=Ae^{i(kx-\omega t)}$ for the de Broglie plane waves for free particles. Basically he does the following.
He assumes that $\psi$ has to be of the form $\psi(x, t)=\cos(kx-\omega t) + \delta\sin(kx-\omega t)$. (H... |
Susskind in one of his lectures at PiTP 2018 on Complexity and Gravity talks about describing black holes as a qubit system, comprising qubits of the order of the entropy of the black hole. This is basically a $\textit{minimal description}$ in the sense that one could basically model the entire, say, AdS space, in whic... |
The presentation I see in the textbooks goes something like this, Maxwell realized changing electric fields produce changing magnetic field and vice versa. Therefore, at least intuitively, one can understand why there should be such a thing as Electromagnetic wave. Which then Maxwell showed, as far as I know, by using ... |
One way to calculate potential (using infinity as our reference point) is to sum all the contributions of charges that are around.
Let's say I want to calculate the potential at some point on charged surface.
At that point, there is some charge (can be infinitesimal) and that charge should contribute something divided ... |
I have a question about modeling sky noise which should be filtered by a spatial filter 4f system. My approach for this task is to use a 2D array with random amplitude values and another 2D array that simulates different phases based on the directional cosine of a plane wave. So my code should create a 2D array where e... |
In field theory, there's no guarantee that the energy-momentum tensor resulting from Noether's theorem is symmetric. The usual trick to construct a symmetric tensor is to add to the original energy-momentum tensor, the derivative of a function of fields that has three upper indices, and which is anti-symmetric in its f... |
Some people said if it is originated from electrons then it is X-ray but if it is originated from the nucleus it is gamma ray. But people can produce X-rays and gamma rays via Bremsstrahlung process and in Bremsstrahlung process it is resulted from decelerating or braking electrons. So, gamma rays produced via Bremsstr... |
The Schrödinger equation is given by:
$$
i \hbar \partial_t |\Psi\rangle = \hat{H}|\Psi\rangle
$$
The right hand side is just an operator acting on a state vector, so we are free to consider its expectation value
$$
\langle \Psi|\hat{H}|\Psi\rangle
$$
which would just be the average of the energies we would measure if ... |
Two particles P and Q are attached to opposite ends of a light inextensible string which passes over a small
smooth pulley at the top of a rough plane inclined at 30° to the horizontal. P has mass 0.2 kg and is held at
rest on the plane. Q has mass 0.2 kg and hangs freely. The string is taut (see diagram). The coeffici... |
I am trying to solve exercise 8.3 from Lightman's problem book, but I don't know where to start to get a sufficient and necessary condition on a field of one forms $\tilde\sigma$ for there to exist a function f such that $\tilde\sigma $ = $\tilde{df}$.
I even tried to understand the solution, but I didn't. Can you help... |
Consider a slider capable of sliding on a rod. The rod has a constant angular velocity of $\omega$, and the slider is moving up the rod with a velocity $v$ and acceleration $a$ with respect to the bar.
If I am standing on the hinge, then I am in the ground frame. Now, in the ground frame there will be a centripetal ac... |
I have a vessel 50% full of ammonia at outdoor temperature of 20F - 100F depending on time of year.
This vessel will be evacuated with a compressor and the vapor will be discharged into an ammonia storage tank. The compressor is capable of pulling enough of a vacuum to evacuate the vessel once the liquid has been evapo... |
Why are iron and copper used more than other materials to make cooking pots?
|
A charged particle near a current-carrying wire does not experience a magnetic force when its velocity is equal to $0$. So why does a compass needle kept near a current carrying wire experience a force when the compass needle is at rest?
|
In the theory of elasticity there is an important object, the displacement increment vector $u_i$. The derivative of such an object can be decomposed into symmetric and antisymmetric parts:
$$
\partial_i u_j = \underbrace{\frac{1}{2} (\partial_i u_j + \partial_j u_i)}_{u_{ij}} + \frac{1}{2} (\partial_i u_j - \partial_j... |
I am dealing with some General Relativity extensions and I am not sure about my knowledge in basic GR since I am having some weird troubles with what I think are basic concepts.
As far as I know, if we have a field equation (we can think about this as, for example, EFE) in vacuum, $R_{\mu\nu}-\dfrac{1}{2}g_{\mu\nu}R=0$... |
In the problem below, why does the second method used to calculate magnetic dipole moment $\vec {\mu}$ essentially use the definition of the electric dipole moment $\vec {p}$? Is magnetic dipole moment the same as electric dipole moment? Can this method always be used? If yes, what is the need to differentiate between ... |
As shown in figure we have two objects , 1 and 2 . Each have a mass of 10 kg and height 1 meter. Suppose i lift object 1 to a height 1 meter. The energy required to lift object 1 is E= mgh ( m is mass, g is gravity , h is height ) E= 10×9.81×1 So E= 98.1 j. Now potential energy of this object is PE= mgh , = 10×9.81×1 ... |
Are there any books that contain what is usually taught throughout an undergraduate physics degree, in one book, or in volumes? I suppose, it won't contain all information about the many subjects taught, although, you can expect with brevity that the majority of undergraduate modules will be taught, just not to the ext... |
The notion that conserved quantities (or quantities for which there is something like a continuity equation) correspond to symmetries of the action of a physical system can be formulated in various different realms (classical mechanics, field theory, Lagrangian / Hamiltonian formalism, QM, QFT ...). When it is formulat... |
From my layman's understanding of Hubble's law, the spacetime between 2 celestial objects 1,000,000 parsecs apart has been observed to increase at a rate of about 73 km/s. Extrapolating from this, on a much smaller scale the spacetime over a distance of 1 meter would be increasing at a rate of 8.51 × 10^-18 km/h.
My qu... |
I was wondering if it is possible to derive Newton's law of universal gravitation, without utilizing Kepler's 3rd law. I have found many proofs that use this type of proof. I read somewhere that Kepler's laws predated Newton to discover the fundamental formula that Newton used for the law, but I was wondering what woul... |
If I have a charge $q$ above a grounded conducting plane, I know I can calculate the potential of the charge using image method. Since the plane is grounded, would the potential below the plane be $V=0$, assuming there is no charge below the grounded conducting plane?
|
The polarizability can be expanded in the from:
In Alkali gases, it is said that $\chi^3$ can be nonzero, and the combination of multiple waves can produce four-wave-mixing.
But what about $\chi^2$?
I've heard it said that even order harmonics typically don't occur in gases because of "symmetries in the time domain," ... |
I want to program a computer simulation of the earth in Python. For example, I can have the earth visible and near infrared albedo, the earth's middle infrared albedo, and from that I can get the temperature, then the other values can variate by $\text{CO}_2$ emissions, cloud variations, methane from the ice caps, ice ... |
We have an action of the form:
$$S=\int d^4x\sqrt{-g}\left(\frac{R}{2\kappa^2}+\frac14F_{\mu\nu}F^{\mu\nu}+\frac12m^2A_{\mu}A^{\mu}\right).$$
Here $R$ is the curvature scalar, $A_{\mu}$ is a vector field, $F^{\mu\nu}$ is the Faraday tensor and ($\kappa,m$) are constants.
Using the variational method I varied the metric... |
The pressure exerted by a fluid at depth is given by:
$$ P = \rho g h$$
The state variables in an ideal gas are related by:
$$ PV = nRT$$
For the second equation, we assume the system is in equilibrium and the state variables are constant throughout the whole container which has the gas. If this is so, then how can we ... |
A cavity, subject to gravity, is filled with a fluid initially at uniform temperature. Initially all boundaries are adiabatic surfaces; at time $t=0$ two opposite boundaries (shown in red and blue) start injecting/extracting thermal energy into/from the system at the same exact rate ($Q_\text{source} = – Q_\text{sink}... |
The Gaussian fermionic integral is evaluated to be
$$
I = \int \prod_{i,j}d\theta^*_i d\theta_j \exp\left(-(\theta^*_iM_{ij}\theta_j+c^*_i\theta_i+\theta^*_ic_i)\right)=N \det M e^{c^*_iM_{ij}^{-1}c_j}
$$
where the $c$'s and $\theta$'s are Grassmann variables.
The fermionic vacuum functional is found to be
$$
\lim_{\ep... |
From reading the answer in Difference between the CKM and the PMNS matrix , I gather that the transition $W\to ub$ where $u$ and $b$ mean flavour eigenstates is not possible, but it is possible where $u$ and $b$ means mass eigenstates. Is this understanding correct?
If this is so, then starting with a $B+$, which is in... |
Imagine that a ball of mass $m$ is launched at a block, which also has mass $m$. Attached to the block, facing the ball, is a massless spring with a massless board at the end. Alternatively, we can assume that the block, spring, and board taken together have mass $m$. Assume there is no gravity and no dissipative force... |
As photons are quantum particles and basically waves in a quantum field, could an infinite number of photons exist in a closed space described by finite numbers? Does the answer to this apply to other fundamental particles as well?
|
We can model the water consumption $\dot{m}_{w}$ of a simple humidifier using the following equations:
\begin{align}
\eta_{hum} & = {T_{db,i} - T_{db,o} \over T_{db,i} - T_{wb,i}} \\
h_{o} & = h_{i} \\
\dot{m}_{w} & = \dot{m}_{a}(w_{o} - w_{i})
\end{align}
where the subscripts $i$ and $o$ denote the entrance and exit o... |
In the following van der Waals formula , would shifting the ideal-gas entropy on the left-hand side create an entropy of vaporization equation? In other words, does the real-gas entropy minus the ideal-gas entropy equal the entropy of vaporization?
P.S. I am trying to calculate b in a van der Waals equation by using th... |
For
$V_2$
, why is there no current flowing from the positive terminal from $V_2$? In other words, why does $I_3$ win out from the current that would be flowing from $V_2$ if it was the only battery in the circuit?
Also, why is the Kirchoff loop ebcde in this diagram oriented this way? Could we not argue that the loop... |
What is the dynamic process of Compton scattering? Does it happen instantaneously? If not, what is the changing physical process?
And why is it postulated that the collision is an elastic one?
|
So I am leaning about various topics like physics like simple machines, center of mass, momentum, energy conservation, equilibrium but the more I study these "upper" level concepts the more I realize that I don't understand the very basic concept of force. Especially, graduating from the simplistic model of viewing obj... |
I am reading Schwartz's book "Quantum Field Theory and The Standard Model", in chapter 8, the author says "A set of objects $\psi$ that mix under a transformation group is called a representation of the group."
I am confused about this, I thought the representation is the representation of the transformation, not the s... |
According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf the big pulsed power accelerator, HERMES III, generate electron beam with peak energy at 22 MeV and average electron energy at 16 MeV and the resulting photon energy which is bremsstrahlung radiation is approximately 2 MeV (actually 1.9 MeV) while in th... |
Given some spacetime dimensions $D$, are there only certain allowed supersymmetry charge nunbers $\mathcal{N}$?
What are the relations of $\mathcal{N}$ and $D$ for the following cases:
When the theory is conformal.
When the theory does not have to be conformal.
When the theory is Lorentz invariant.
When the theory ... |
in QM lecture we are told that the average value of a quantum state in a mixed state is (when system is in state $|\psi_j\rangle$
with probabiity $p_j$ and given total probablitiy $\sum_j p_j=1$ is
$\langle \hat{A}\rangle=\sum_i p_i\langle \psi_i|\hat{A}|\psi_i\rangle$
which is something that is understood to me. then ... |
Here is the question:
"A particle with mass m is given an initial velocity $v_0$ so that it moves in a straight line (you can consider it positive). It is subject only to a force that is inversely proportional to the square of
its speed, as $F = −c_xv^2$.
(a) Write down Newton’s 2nd law for the particle, and the corre... |
I understand how the magnetic field and electric field (around a current-carrying conductor) swap their roles depending on the frame of reference, due to the effect of length contraction (in the special theory of relativity); however, this question has been troubling me.
Consider two charges separated by a vertical dis... |
This question is about Kim et al. delayed choice quantum eraser experiment.
Is it possible to adjust the phase of interference fringes from $D_1$ and $D_2$ by adjusting the distance of $D_0$ screen?... Shouldn't they be in the same phase? Why is there a $π$ phase shift?
Is it possible to adjust the phase of them and... |
I watching a video that mentioned that a meteor loses mass as it falls via energy being converted to heat, so say we are on the Burj Khalif ($828$ meters), how many times would a human, say $6$ ft tall and weighing $150$ lbs, have to fall from the top to lose all of their mass (including or excluding things like metabo... |
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