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All articles I found explain a human male erection through biological mechanism. However I am still curious how such process can make the male sexual organ "stand up" during an erection.
From what I understand, during an erection, there are more blood in arteries but wouldn't it make it heavier and thus should not be s... |
Linear velocity vector is $\vec{v}$ and the distance vector is $\vec{r} $.
How is it that angular velocity vector is $\vec{ω}$ = $\frac {\vec{r} × \vec{v}}{|\vec{r}|^2}$
The equation I am aware of is $\vec{v}$ $=$ $\vec{r}×\vec{ω}$. I tried taking a dot product on both sides, cross product etc but I wasn't able to de... |
I am reading this paper "Quantum Raychaudhuri equation" by S.Das.
In this paper, the author derives a quantum version of the Raychaudhuri equation which has nice implication on the focussing theorem.
It seems that it is valid only for non-rotating spacetimes: is it correct?
Has it been extended also to the rotating cas... |
Before i proceed to my question, I want the reader of this question to try out this little experiment at home.
Take a cup or mug filled with water ( does not depend how much you fill the cup or the mug ). Start pouring the water out of the cup very slowly ( as much slow as you can, but make sure the pouring of water is... |
A wheel of radius $a$ is rolling along a muddy road with speed $v$. Particles of mud attached to the wheel are being continuously thrown off from all points of the wheel. If $v^2> ag$, show that the maximum height above the road attained by the flying mud will be $$h_{\max}=a+\frac{v^2}{2g}+\frac{a^2g}{2v^2}.$$
Expla... |
From what I currently understand given a general state vector $|\psi\rangle$ the wave function:
$$\psi(x) = \langle x|\psi\rangle$$
represent the vector $|\psi\rangle$ in the base of the eigenvalues of the position operator. Similarly the wave function
$$\psi(p)=\langle p|\psi\rangle$$
represent the same vector but in ... |
Having recently learned about the Casimir effect I began to wonder about spacetime and the effect of intervening bodies on gravitational forces:
Does a mass have a "shadow" behind it or some sort of "dampening" effect on gravitation from body C as sensed at point A with body B in between?
In relation to the Casimir e... |
My professors note on vertex function make some doubts in me,
$$\Lambda_\rho(p,q,p')=\frac{e^2 \gamma_\rho}{3\pi^2}R(a)$$,Where $\Lambda_\rho(p,q,p')$ is the electron-photon vertex at one-loop level
,
In terms of the fine structure constant $\alpha(a) = \frac{e^2(a)}{4\pi}$ the one loop contribution
to the QED vertex c... |
for a standard rectangular wave guide, which a > b (horizontal dimension > vertical dimension), the dominant mode is supposed to be TE10/TM10 mode.
If we flip the direction, make b > a (vertical dimension > horizontal dimension), does this make dominant mode become TE01/TM01?
the definition of dominant mode states that... |
Suppose a particle with a gaussian wavefunction moves to begin with towards a position detector screen. How do we obtain the 'Time of arrival' distribution, when time can't be an observable? Should the average time of arrival be inversely proportional to the mean of momentum distribution? Does having a wide initial loc... |
I probably learned that back in university when studying general relativity, but I forgot so I want to ask: As far as I understand it, any energy concentration creates a gravitational field, whether that energy is matter, electromagnetism or other energy, right?
The unit of gravity is meters per second^2.
Issac Newton'... |
I have 2 functions for the $x$ and $y$ components of the velocity of an object ($z$ should always be $0$ in this case)
$$V_x(t)=v_{xi}+\int_0^ta_x(t')dt'$$
$$V_y(t)=v_{yi}+\int_0^t(-g+a_y(t'))dt'$$
and a function for the magnitude of $a(t)$:
$$a(t)=\frac{T}{m-t\frac{T}{I\cdot g_0}}$$
$a(t)$ is always in the opposite di... |
I'm looking to calculate the diameter of a liquid after being poured on a flat surface, in terms of:
Time - t
Viscosity - η
Density - ρ
Volume poured - V
Basically, assume you were to carefully pour a liquid (ex. water, milk, oil) onto a flat surface (ex. a glass sheet) and measure the diameter of the puddle over time.... |
I'm trying to understand the deflection of light due to an axially symmetric gravitational lens following chapter 2.3 of these Heidelberg lecture notes. In doing so, I encounter the integral (2.12 a)
$$\int_0^{2\pi} \frac{r - r'\cos(\phi)}{r^2 + r'^2 - 2rr'\cos(\phi)}\,d\phi$$
which apparently vanishes for $r'>r$ and i... |
There are a lot of questions on this site about the double slit experiment, none of them answer my question specifically. I am not asking about detection or detectors or anything just at the slit. My question is about the photons traveling as partial waves through both slits and the dots on the screen. A lot of the ans... |
In the context of nuclear physics, a physicist wrote in a non large audience document (not available on the web nor in books) that the free nucleons don't interact with each other while they do in matter (nucleus, nuclear matter, neutron stars, etc.)
Is it true ?
If it is true, is the difference of behaviour understood... |
Pt.1: A particle moves in one dimension under the action of a force F(v) per unit mass. Explain how you would compute the speed $v$ of the particle, and its position $x$,at time $t$.Suppose $F(v) =k(v_0+v)$, where $k$ and $v_0$ are two constants. Find $v(t)$ and $x(t)$ assuming that the particle starts from rest at the... |
I see this question was asked several times before but I don't think any answer can explain the issue perfectly. I am studying many body theory and encounters finite temperature Green's function. At first glance, it seems to me that the correct time dependence of, let's say a greater green's function, would be
$$
\begi... |
I stumbled upon this question:
Can we really not tell if we are moving?
and it made me start thinking (probably a bad idea for a non-physics guy).
To my knowledge, moving at relativistic speed means that time passes slower than for a non-moving observer. My question is, can't this be used to determine whether we are mo... |
First let me say that Physics is not my area of expertise and my knowledge from school is pretty rusty, so I apologize in advance if I am asking a totally stupid thing or I have a mismatched understanding of basic concepts. Please treat this question in terms of Newtonian physics, not looking for any relativistic answe... |
On page 54 of Weinberg's QFT I, he says that an element $T(\theta)$ of a connected Lie group can be represented by a unitary operator $U(T(\theta))$ acting on the physical Hilbert space. Near the identity, he says that
$$U(T(\theta)) = 1 + i\theta^a t_a + \frac{1}{2}\theta^a\theta^bt_{ab} + \ldots. \tag{2.2.17}$$
the... |
I've taken two photos of a metal in an experimental setup.
The first image shows the metal illuminated by a halogen-lamp from above. The second image shows the same metal illuminated by the same lamp but there are two additions: There is a linear-polarizing filter in front of the lamp and one in front of the camera.
... |
In https://arxiv.org/abs/hep-ph/0010057 the following vector calculus equality is claimed without proof although in note [4] the cryptic comment is made that "The relation is essentially the momentum space identity $(\mathbf{k}\times\mathbf{A})^2=\mathbf{k}^2\mathbf{A}^2-(\mathbf{k}\mathbf{A})^2$ in position space":
... |
In reading 14.4 of Gregory Moore's notes on abstract group theory, I was left with some questions on the computation he did of the path integral that may be general features.
Let consider a spacetime $M=\Sigma\times[t_0,t_f]$ on which we have a space of fields $C^\infty(M)$. Let $\mathcal E_1$ be the set of fields $\ph... |
The solutions to the gravitational two-body problem can be described by conic sections.
In particular, two abstract point masses don't collapse into each other (that is, do not get arbitrarily close to each other) except for the special case where they move on a one dimensional line.
Could this property be deduced with... |
At 6:47 of this video lecture, the professor defines enthalpy for a constant pressure process as
$$ q_{p}= \Delta U + p \Delta V$$
but, I can not understand why the work he implicitly starts referring work as an exact differential. Is this due to it being the reversible kind of work?
and around 36:55 of this lecture, a... |
Imagine a closed system with a black body and a black hole, where the black hole has a lower temperature. The black body will radiate heat and the BH will absorb that heat, gaining mass in the process. The obvious catch is that the BH's temperature is actually sinking as it's absorbing heat energy. Which means it can d... |
Does that happen, on occasion? Does anyone know?
I suppose it is quite rare, ... To absorb three neutrons without once fissioning...
Could U-235 absorb three neutrons at once? Or just one, becoming U-236, then two at once?
|
Neutrinos are detected when they 'hit' a nucleus and are re-directed (z-boson) or 'create' a leptons that matches the type of neutrino....
What happens when the neutrino(s) in a neutrinoless double beta decay are (re)absorbed by the nucleus? Does the nucleus have to emit a third electron?
|
It is theorized that during inflation gravitational waves are produced. See this article by Guzzetti, Bartolo, Liguori, and Matarrese (Cornell University). Or this one by Liu, Guo, Cai, and Shiu (Cornell University). Primordial gravitational waves are produced and proven to exist
Recent observation of B mode polarizat... |
The classic picture of the band structure for an insulator is a filled valance band below $E_F$ and empty conduction band above $E_F$.
This picture seems to me that the electron density is fixed. For example, at $T=0$, $n=\int_0^{E_m} d\epsilon D(\epsilon) $, where $D(\epsilon) $ is density of state and $E_m$ is the m... |
As is discussed in this question and this other question, it is possible to construct Lorentz boosts along an arbitrary direction using only the Lorentz boost along the $x$-axis by performing the following procedure:
(1) Rotate the coordinate axes to align the $x$-axis with the direction of the boost.
(2) Perform a boo... |
Is it plausible that a possible extraterestrial scientist from a galaxy 13 bilion light years from us sees this part of the universe nothing else than just background cosmic radiation... and even more intriging in the oposite direction he sees an enormous portion of the universe filled with galaxies and stars that are ... |
So I was solving a problem where there was a parabolic conductor lying in a region of uniform magnetic field (B) and a conducting rod was sliding on it, and its acceleration was given by 'w'.But how can an emf be induced in parabola despite of the fact that it is not a closed loop?
|
I think in some media, light can be significantly slowed down; but even if only slightly, where would the momentum go when the light slows down and where does it get the extra momentum when it leaves that medium? An example is a water.
|
Why it is essential to set a particular direction for an OPTICS axis of a crystal (e.g. Calcite)? What is the importance of that direction?
|
I was told that
If net external moment of some forces is zero about a point, then the net external force passes through the point.
I know it's not true in general, what was the special condition imposed which I forgot to include to make it true? Also, is there anything close to the statement we can say?
Some of my fr... |
I am starting to studying quantum physics, but this part of the theory catch me, how do we go from the $-e^2/2a_0$ to the next expression?
$$ E=\frac{1}{2}\left(\frac{e^2}{a_0}\right)-\frac{e^2}{a_0}=-\frac{e^2}{2a_0}=-\frac{1}{2}\alpha^2mc^2=-R_\infty$$
This is the energy of an electron in the hydrogen Bohr atom:
$e$ ... |
Standing waves are the waves in which disturbances do not simply propagate forward or backward, but rather the material particles are moving up and down continuously, with the particles between two consecutive nodes in the same phase. But when we are talking about the harmonics of such a wave, we define the $n^{th}$ ha... |
at 53:13 of this lecture by mit ocw, the prof. Moungi Bowendi writes,
$$ (\frac{\partial U}{\partial T})_{p} = (\frac{\partial U}{\partial T})_{v} + (\frac{\partial U}{\partial T})_{T} (\frac{\partial V}{\partial T})_{p}$$
Before this he wrote,
$$ U(T,V(p,T) )$$
i.e: U is a function of both temperature and volume with... |
When displaying experimental data on a graph, must both axes use the same number increment intervals, which would be variable with the size of the interval? Or (because a graph represents experimental data) can the scales on the two axes be different and reflect the precision of the instruments used to collect the data... |
A rod of length 'l' and cylinder of radius 'r' is kept on an incline plane
as shown in the figure. The rod is pivoted, while the cylinder can roll
without slipping. A light string PQ attaches top of cylinder to some
point on the rod such that it is parallel to the incline. The minimum
value of radius of cylinder to ens... |
In most textbooks and thermodynamic lectures, the pressure is defined as the force on the walls of containers due to the incassecant beating of gas molecules divided by the area of the wall. Now, suppose I take a random point inside the container, what would be it's pressure at equilibrium and also non equilibrium cond... |
In SR we've learned that the time dilation for an observer moving clock w.r.t one fixed in a frame at rest is
$$\tau = \gamma \tau_0 = \frac{\tau_0}{\left(1-v^2/c^2\right)^{1/2}}$$
ref: "Special Relativity - A.P. French" and many others
In this case being gamma > 1, it implies delta t < delta tau
No moving to GR, the b... |
I used a $\rm NaI$ scintillation detector to linked to a scalar unit that counts the number of gamma rays detected from a $^{22}$Na source. I repeated the experiment for equal time intervals of 40 seconds at a variety of different distances from the source ranging from 0.02 to 0.5m.
I subtracted an average background c... |
Pls explain the intuitive concept of centrifugal force in different situations.
|
Suppose there is a piston as shown below,
And, let's say that I press down on the piston using one finger, this compresses the gas inside.
Now, in usual thermodynamic textbooks, we say that the force exerted by piston on gas is equal to the pressure of the piston on the gas times area of the piston but, here, I have a... |
Why does gravity act at the centre of earth and how does that happen?
|
In a Crookes tube there is a cathode and a cross shaped anode.
The anode attracts the electrons so why do some electrons pass the anode to strike the screen behind.
It's not as if the cathode is shooting electrons out like a gun, they are following field lines from the cathode to the anode.
Also the electrons that do p... |
Description of the problem
I want a projectile launched at speed $v_0$ at angle $\theta$ above the horizontal to just make it to the top of a building of height $h$ and a distance $d$ away. What $\theta$ should I use?
What have I tried?
Let $t^*$ be the moment when the projectile just makes it to the top of the buildin... |
I've been thinking about What is the minimal equipment required to observe the Apollo lunar retroreflectors? for a while and every time I start to estimate the strength of the received signal I choke because I don't know which terms are most important.
For the purposes of my question lets assume a 532 nm diode pumped s... |
When an object is thrown upward with some velocity then it doesn't fall towards the earth until the given velocity becomes zero.
Now imagine the case given in the figure
There is a question in my book asking for the time taken by the block to slide down the incline if it is released from the top of the incline. And th... |
Fig.: Conductive bar moving along a conductive rail. The bar is
shielded from magnetic induction by a highly permeable, insulated cylinder.
I know if a conductive bar moves on a conductive rail
with velocity v through a constant magnetic field B then the
induced voltage is $vlB$.
($v,l,B$ are perpendicular each other,... |
With the energy emitted by the sun in 1 second, how long could everyone household on earth be powered?
Currently we obviously can't harvest 100% of the sun's energy emissions.
|
$$ ( P + \frac{n^2 a}{V^2})(V-nb) =nRT$$
is the van der Waals equation of state
and,
$$ PV=nRT$$
is the ideal gas law.
Similar to how I asked in this stack , prof. Moungi Bawendi says that as we drop pressure to zero by some mechanism, the product of pressure and molar volume converges to some constant based on the tem... |
here potential is said to decrease from a to b ,why it is so and why there is potential drop from a to b please explain?
|
I understand that for a double slit experiment the equation is $\lambda=xd/L$, which has come from the small angle approximation of $d\sin\theta = n\lambda$ by assuming that $\sin\theta = (x/L)$ and therefore can be subbed in. I don't get why this doesn't work for both single slit diffraction and especially multiple sl... |
My question might be based on a confusion of what counts as a measurement... But anyway the flavour eigenstate of a neutrino is a superposition of mass eigenstates $v_1$ and $v_2$. This is given by:
$|\nu_e\rangle = U_{11}|v_1\rangle + U_{12} | v_2 \rangle $
$|\nu_{\mu} \rangle = U_{21}|v_1\rangle + U_{22} | v_2 \rangl... |
The two specific equations I’m asking about were stated at an introductory stage in the famous 1905 paper which launched Special Relativity. He didn’t explain how this derivation was arrived at; all I wish to understand is what his direct explanation would have been. The equations were:
$t_B - t_A = r_{AB}/(c - v)$
$t^... |
In David Tong's lecture notes on quantum field theory, at the bottom of page 138 he states that, regarding the coupling of the electromagnetic field to a real scalar field, there exists "no suitable conserved current... This means we can't couple a real scalar field to a gauge field".
I don't understand what this means... |
\begin{equation}
\mu \frac{\partial{e}}{\partial \mu }=\frac{{e}^3}{12\pi^2}=\beta({e})\end{equation}
This is the equation for beta function in quantum electrodynamics, it tells us about how coupling constant scales with the scale $\mu$.
The solution to this equation is
\begin{equation}
{e}^2(\mu)=\frac{{e}^2(\mu_0)}{1... |
As a graduate student of physics in the early 2000's, our particle physics classes started with quantum field theory, since QCD had long been established as a good model of the nuclear strong force. We sometimes talked about the S-matrix, but as a part of quantum field theory, not an alternative to it: we evaluated Fey... |
Can a fermion get converted into a boson?
|
Q) A plane spiral made of stiff smooth wire is rotated with a constant angular velocity $\omega$ in a horizontal plane about the fixed vertical axis O. A small sleeve M slides along that spiral without friction. Find its velocity $v'$ relative to the spiral as a function of the distance $r$ from rotation axis O if the... |
Are both centrifugal force and Coriolis force really fully explained by what is called "frame dragging" in GR? And if that is correct, does this concept "frame dragging" solve the problem of considering the motion of an observer on a rotating disc is in an absolute motion state? And is it the case in linear acceleratio... |
For a long time it was thought that anomalies for a group $G$ were classified by $H^n(BG)$, although it is now understood that they are in fact classified by $\Omega^n(BG)$.
On the other hand, Dijkgraaf and Witten argue that Chern-Simons terms are classified by $H^4(BG)$, although given the relation between anomalies a... |
Special relativity predicts that for me and my friend who's running at a uniform speed of $v$ away from me, the same things don't happen at the same time. For instance, if my friend runs at a light bulb who's set to light up in a few seconds, the light bulb is going to light up 'earlier' for my friend. Is it possible t... |
Here's my layman thought process:
By emergence and the second law, new "modes" or points in configuration space become "unlocked" with macroscopic systems. One is a brain, which can have an experience or memory ontop of just being an assemblage of x microscopic particles.
The counter point might be that it takes x part... |
As far as I know, there are no known observations that require a quantum theory of gravity. Now, that's not to say we don't need a quantum theory of gravity. In fact, I get the sense that we do, at least in part, because GR couples energy density to spacetime curvature, so we expect spacetime to be influenced by quantu... |
Are there examples of the Peltier effect occurring naturally, or has it only ever been artificially produced? Has there ever been what amounts to a 'natural refrigerator' discovered? And what would be the likelihood of finding such a thing if we haven't already?
|
Planck's Law is commonly stated in two different ways:
$$
u_\lambda \left( \lambda, T \right) = \frac{2hc^2}{\lambda^5} \frac{1}{e^\frac{hc}{\lambda kT}-1}
$$
$$
u_\nu \left( \nu, T \right) = \frac{2h\nu^3}{c^2} \frac{1}{e^\frac{h\nu}{kT}-1}
$$
We can find the maximum of those functions by differentiating those equatio... |
Consider an asteroid of mass $m$ rushing towards the earth. What is the mathematical condition under which the asteroid will be captured into an orbit around the earth (given that the asteroid and the earth are the only astrophysical objects in the universe)?
Additions after existing answer According to the current ans... |
At 12:20 of this video lecture, while proving temperature and heat relation using a paddle wheel and hanging a mass to it, professor Bob Field writes down the change in temperature as $\Delta T = \frac{Q}{C_{p}}$ that is he says that the "change in temperature" is Work done divided by the Specific heat capacity at " co... |
I understand that current leads voltage by 90° in capacitor.
How does one show that it is true by an experiment?
|
There's a hill on a route I plan to cycle soon. I've done it before and it's a killer. I'd like to prepare for it with indoor training to see if I'm ready.
The hypotenuse of the hill is about 0.2 km and the gradient of the hill is 15%. Last time I did it, it took me 52 seconds at a speed of 13.8 km/h.
I figure I can re... |
I have two identical point light sources A & B emitting the same frequency. They are equidistant from the single slit and from the line passing perpendicularly through the middle of the slit towards the screen. The light from the single slit is focused onto a screen a sufficient distance away for fraunhofer diffraction... |
I have 5 polarizers in series. The first polarizer is vertical. The second polarizer makes an angle of 45 degrees from the first polarizer in a clockwise sense. The third polarizer makes an angle of 45 degrees from the second polarizer in a clockwise sense and so on. The fifth polarizer will again be vertical.
My quest... |
I have the state $\left|\psi\right.\rangle = \alpha\left|\right.0\rangle + \beta\left|\right.1\rangle$.
I want to show that there is a direction $\vec{n}$ for which the spin is $+1$, so $\langle\vec{n}\cdot \vec{\sigma}\rangle = 1$.
I started by calculating the expectation value of the general matrix $$A=\begin{pmatrix... |
In case of a single free particle, no potential field, the wave function is:
$$ \Psi = A e^{i(kx-\omega t)}. $$
As it must fulfill the Schrödinger equation
$$ - \frac{\hbar^2}{2m} \nabla^2 \ \psi(\mathbf{r}, t) = i\hbar\frac{\partial}{\partial t} \psi (\mathbf{r}, t) $$
it follows the restriction:
$$ \frac{\hbar^2 k^2}... |
In section 5 of their 2000 paper "Nambu Mechanics in the Lagrangian Formalism", Ogawa & Sagae critique previous attempts by Bayen & Flato and by Takhtajan to formulate the theory with a single Lagrangian, arguing instead that the proper generalization of Lagrangian classical mechanics is to introduce multiple Lagrangia... |
When trying to derive the probability density from the Pauli equation, I face a problem.
Starting from the Pauli equation
$$ i\hbar \frac{\partial \Psi}{\partial t}=\hat H_0 \Psi +\mu_B \ \hat \sigma \cdot \mathbf{B} \Psi, $$
I need to adjoint it:
$$ -i\hbar \frac{\partial \Psi^+ }{\partial t}=\hat H_0^* \Psi^+ +\mu_... |
Say I've an operator $\hat \sigma_{11} = |1\rangle \langle1|$. Now say we calculate the variance of $\hat \sigma_{11}$. So we have,
$$\langle (\Delta\hat \sigma_{11})^2 \rangle = \langle \hat \sigma_{11}^2 \rangle - \langle \hat \sigma_{11} \rangle^2 = \langle \hat \sigma_{11} \rangle - \
\langle \hat \sigma_{11} \rang... |
Assume there is a neutron star with a magnetic field and no net electrical
charge. What happens to the magnetic field if it gains some mass and
collapses into a black hole?
|
I was thinking while trying to sleep and I suddenly asked myself the following question. I couldn't figure out the answer.
Question: Think that we are in space with a ball (or particle) and an inclined plane (the angle of the plane doesn't matter). Imagine that the ball is coming through the plane with a constant veloc... |
Two charged bodies create a superposition of electrostatic fields at a point and there is no evidence of fields interference. Now, if we put two current circuits around the charged bodies then we create also magnetic fields and as a consequence two electromagnetic fields. If the electrostatic field and the magnetic fie... |
At some point of Polchinski book, we are interested in calculate the following correlation function: $$\left\langle \prod_{j=1}^n[e^{ik_i\cdot X(z_i,\bar{z}_i)}]_r\prod_{j=1}^p\partial X^{\mu_j}(z_j'))\prod_{k=1}^q\bar{\partial}X^{\nu_k}(\bar{z}_k'') \right\rangle$$
In which the fields $X^\mu(z,\bar{z})$ are such that... |
I'm quite confused with Laplace pressure. I know the formula is (at least considering a spherical surface)
$\Delta P = P_{in}-P_{out} = \frac{4\sigma}{d}$. What exactly is the surface you have to consider? And I've heard and read that this is the pressure that occurs when two different phases meet, how do I know which ... |
After solving the Schrodinger Equation and getting the stationary states (separable solutions), we say the the general solution of the Schrodinger Equation is just the linear combination of these separable solutions.
My question is: How do we know that it is exhaustive, i.e., covers all possible solutions for the wave ... |
We have:
$\sigma = E \epsilon$ and $\epsilon = \Delta L/L_0$. This seems to imply that for a constant strain, we will achieve a proportional change in length.
However, it doesn't rest well with me that this relation is not dependent on $L_0$. For instance, say I have some material that has an $E = 1$ MPa and an area of... |
I know that Einstein’s theory of general relativity predicts that the wavelength of electromagnetic radiation will lengthen as it climbs out of a gravitational well. Photons must expend energy to escape, but at the same time must always travel at the speed of light, so this energy must be lost through a change of frequ... |
Question:
I was reading this analogy of Fermat's Principle of Least Time:
In Figure, our problem is to go from A to B in the shortest time. To illustrate that the best thing to do is not just to go in a straight line, let us imagine that a beautiful girl has fallen out of a boat, and she is screaming for help in the w... |
The Reissner-Nordström metric is given by $$g = -h(r)\,{\rm d}t^2 + h(r)^{-1}\,{\rm d}r^2 + r^2\,{\rm d}\Omega^2,$$where ${\rm d}\Omega^2$ is the round metric on a unit sphere $\Bbb S^2$ and $h(r) = 1-2mr^{-1}+qr^{-2}$, where $m\geq 0$ is a mass and $q\in \Bbb R$ is an electric charge ($q=0$ gives a Schwarzschild black... |
As we go towards the center of Earth the gravity weakens. Does that mean that due to absence of gravity the outer part of the inner core exerts a pressure against the inner part of the outer core of Earth as the inner core rotates very fast and feels a centrifugal force on their volume?
|
In Page 63, Section 2.5 of Weinberg's QFT Volume 1, on "One-particle states", he considers the representation of homogeneous Lorentz transformation, $U(\Lambda, 0) \equiv U(\Lambda)$
$$
U(\Lambda) \Psi_{p, \sigma}=\sum_{\sigma^{\prime}} C_{\sigma^{\prime} \sigma}(\Lambda, p) \Psi_{\Lambda p, \sigma^{\prime}}
$$
then h... |
As shown in the figure, a uniform chain of length is placed on a smooth horizontal table, and /4 of it is hanging down on the edge of the table. After letting go, the chain starts to slide down the edge of the table from a standstill. What is the speed at which the chain slides to the edge of the table just after leav... |
This is a problem I saw in a stat mech textbook, and I think it is a fairly common problem.
Given the entropy function: $$S = - \sum_{i=1}^N p_i \log p_i$$
Maximize $S$ subject to constraints:
$$ \sum_{i=1}^N p_i = 1 \\ \sum_{i=1}^N p_i e_i = c$$
It was suggested to solve this problem using Lagrange multipliers. So thi... |
I've read that nuclear fusion is what generates such large quantities of solar neutrinos.
Also saw that it was recently experimentally confirmed that two types/energies of neutrinos are generated in the sun via two types of fusion: proton-proton and CNO-fusion. https://www.livescience.com/rare-solar-cno-neutrinos-detec... |
The following plot shows data collected from a Co-60 coincidence experiment. The detectors used were NaI(T) scintillation detectors.
One detector was gated around the 1.33 MeV peak and the second detector collected the data shown below. I have been trying to figure out what the two peaks are around 200keV.
|
This document
https://arxiv.org/abs/1008.4884
presents in Tables 2 and 3 the mathematical expression of many dimension-6 operators,
for example (just an example)
The mathematical expression does not help so much to visualize the corresponding expression (in particular those who have a derivative).
Are there Feynman di... |
What are the charges of all the planets
in our solar system and what are the charges of whole universe, solar system and milky way etc..
|
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