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8 views

Does the timeline of earth changes if Gravity exceeds 15g instead of 9.8g?

as we present a timeline to be the 4th dimensions will the dimension changes simply changing the gravity? lets say 9.8g to 15g what will be the impact on the timeline as we represent timeline as ...
1
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1answer
6 views

Negative pressure in general relativity

Is there an intuitive way to understand what negative pressure means in general relativity in the same way as positive pressure can be thought to be kinetic energy of gas particles? Dark energy has ...
0
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1answer
12 views

I am confused about image formation of object on itself by a system of lens and a mirror

If there is a lens and a mirror. An object is place in front of this system (nearer to lens), if final image of object( refraction, reflection and again refraction) is forming on object itself, then ...
0
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0answers
14 views

The change in mass of a black hole do to Hawking Radiation

Hawking radiation which is the result of virtual particles, which are always created in pairs,(particle/antiparticle) near enough to the event horizon of a black hole, that one of the pair falls in ...
0
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0answers
7 views

Which book (or article) has detailed calculation for Quantum Heisenberg Model for three or four spins? [on hold]

A I need to write a program to calculate Quantum Heisenberg Model for any number of spins (with or without external magnetic field). I know how to do this calculation for two spins. Which book (or ...
1
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0answers
8 views

Heat-bath algorithm of 2D XY model

Can anyone suggest any reference where the heat-bath algorithm for the classical 2D XY model has been discussed in detail. I have found references for the 3D Heisenberg model which can be exactly ...
0
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0answers
15 views

Minimum calculus for Lagrangian Mechanics [on hold]

I have noticed in my classical mechanical books, the development of the motions of equation for simple systems using the Lagrangian that the main complication, if doing the work by hand, is applying ...
1
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0answers
13 views

Show $\langle \alpha| (\cos \mu)^{-a^{\dagger} a} | \alpha \rangle =e^{|\alpha|^2(\frac{1}{\cos \mu} -1)}$ for coherent states $|\alpha \rangle$

I am reading"Quantum continuous variables, A primer of Theoretical Methods" by A.Serafini, page 120. Let $ a $ be the annihilation operator for the Fock basis. I want to show $$\langle \alpha| (\...
0
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0answers
21 views

Does frequency of light change in the LIGO interferometer arms?

There are a number of questions on the internet and on this site asking about how the LIGO interferometer measurement works given that the gravitation wave stretches both the length of the ...
0
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0answers
22 views

Does a crushed ice cube and a regular ice cube have different potential energies?

For a question on an heat transfer experiment on melting ice cubes in water and measuring the temperature decrease in water, there was a question that asked: Suggest the effect, if any, of crushing ...
0
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0answers
10 views

The transversality axiom in Lieb's Thermodynamics paper

I'm reading The Physics and Mathematics of the Second Law of Thermodynamics and have a question about the T4 transversality axiom which is writtern on page 54. T4) Transversality. if $\Gamma$ is ...
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0answers
23 views

Lifting the square root of a Lagrangian with potential creates cross-terms?

In a personal research project, I have derived the following Lagrangian density. $$ \mathcal{L}=\sqrt{\eta^{\mu\nu} \partial_\mu \phi\partial _\nu \phi} + im\phi. \tag{1}$$ When squared, my result ...
-2
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0answers
19 views

Calculate the time taken for a body to hit earth's surface [on hold]

Find the time taken for an iron cube of dimensions 0.1m × 0.1m × 0.1m, whose density is 7.85 g/cm³ to reach the earth's surface released from a height of 10m from earth's surface, provided gravity = 9....
0
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2answers
48 views

What is the value of the inner product $_x\langle+|-\rangle$?

I know that $\left|_x\langle+|-\rangle\right|^2 = 1/2$, so is it just as simple as taking the square root of $1/2$? Thanks.
0
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0answers
11 views

Electric field inside a homogenous distribution for slightly different Coulomb's law

I am trying to show that the electric field inside a homogeneous distribution of superficial charge is of the order of magnitude of $\delta$, with: $$V(\textbf{r})=\int d^3\textbf{r'}\frac{\rho(\...
-1
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0answers
14 views

Capacitance and energy transfer

Capacitors: Using direct current I apply a voltage, Vo, to a capacitor of capacitance C. It acquire a charge of Qo. I remove the charging source and I connect both sides of the capacitor to another ...
1
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0answers
17 views

Superconductivity as a macroscopic phenomena

I have been doing some reading on the formulation of BCS superconductivity. From what I understand, an additional non-vanishing term $\Delta c_{\uparrow,k}c_{\downarrow,-k} + c.c$ develops below the ...
0
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1answer
52 views

What exactly is a gluon doing when acting as an gauge boson?

The question is in the title. I know that, e.g., W bosons change the flavour in electroweak processes. What do gluons do?
0
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0answers
38 views

As a returning adult learner from engineering and math background, what recommendations to get the basics on QM?

I'm building up the foundations to work on quantum mechanics. I am comfortable with the wave function and the PDE aspect of the field, but my mathematical background, though it covers linear algebra, ...
1
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1answer
42 views

Given the action, derive the Lagrangian (Fields and non-fields)

Let us denote $L$ the Lagrangian, and $\mathcal{L}$ the Lagrangian density, and the action $S$. It is common to find the action based on the Lagrangian. Here, however, I am interested in the reverse ...
2
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0answers
52 views

Initial conditions in QM

My questions are about initial conditions in QM in experiment and in lab. We consider many different initial wave functions, and we solve the problem on paper. Now, I have 2 questions about this in ...
-7
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0answers
59 views

There was no Big Bang [on hold]

It wasn’t an explosion. The composition of the Universe is missing 94.6% of the required material to cause a Big Bang. LIGO Satellites with 25 million mile long legs, in a rtriangular formation ...
-5
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0answers
44 views

Black Body Emission Curve and Self Heating [on hold]

Sorry that the original question is not as clear as it should be. How much would self heating of a blackbody (via kinetic heat energy) effect a blackbody emission curve in equilibrium? ie: Is it ...
0
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0answers
34 views

Schwinger paper about charge in QED

I would like to find the paper by Schwinger where he discusses analytic properties of physical values in the limit $e\rightarrow 0$ and physical meaning of $e^2$ sign. I know only that this paper was ...
0
votes
1answer
26 views

Can temperature difference in a conductor induce charge in it?

Assume a metallic rod which is heated on its right end to maintain a constant temperature gradient in the rod. Now if we take any crossection in the rod,the right side part of the cross section has ...
2
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5answers
72 views

Why is it assumed that magnetic forces arising from magnetic fields do not do work on a current carrying conductor?

Imagine a long, thin current carrying conductor carrying a current I and moving through space with a velocity $v$. If there exists a magnetic field such that there is a force on the current carrying ...
0
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1answer
54 views

Why is $\Delta^0$ not decaying weakly?

Given the lower decay I wonder why it happens this way. Wouldn't it be possible to decay via a weak process as well?
1
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2answers
49 views

Difference between left- and right-handed, helicity and chirality

What is the difference? I know there is the (almost) same question What's the difference between helicity and chirality? but when a particle is given as left-handed. Is it helicity or chirality?
0
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1answer
40 views

Symmetry reason why magnetic dipole transitions are suppressed

In the theory of light-matter interaction, electric dipole transitions between two atomic states of same parity are forbidden. This is because the Hamiltonian conserves parity. Is there a symmetry ...
1
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0answers
43 views

The origin of normal reaction

I want to know what actually is the origin of normal reaction between 2 objects. i have read about normal reaction from several books which generally mention it as a component of contact force which ...
0
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1answer
63 views

What causes objects to appear “black”?

To my understanding, the reason objects appear of a certain color is because it is the color (in visible light) that is absorbed least by the electrons in the material's atoms, and the rest is ...
-8
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0answers
39 views

Time travel is possible? [on hold]

Is the time travel theory of Einstein practical?If yes,then how can we travel faster than light ?
-1
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1answer
63 views

Kinematics problem, only energy related approach [on hold]

I read this question: From the top of a tower, a stone is thrown up and it reaches the ground in time $t_1$. A second stone is thrown down with same speed and it reaches the ground in time $t_2$. A ...
0
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0answers
42 views

Is my thinking correct for partial derivatives and tensors?

So I was transforming the affine connection and I ended up with a term like this: $$ \frac{\partial^2 x'^a}{\partial x'^b \partial x^p} $$ where $x$ and $x'$ are two different coordinate systems ...
0
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2answers
58 views

How do elecrons move?

Do elecrons move from low to high potential or they move due to attraction by positive charge? Or is it something else, what actually happens in flow of electricity.....the concept is just so ...
0
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1answer
35 views

Is a force on the edge of a disk also a torque if the disk is not constrained?

Suppose you have a disk in a vacuum that is completely unconstrained (not fixed at its center). If you apply a tangential force at a point on the circumference of the disk, does the force act purely ...
1
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1answer
22 views

Magnet position for maximum voltage in an ac generator (Lenz's Law)

Animated gif credit The picture above shows, that the voltage of a phase is greatest, when the magnet alligns with the coil of the phase. Why is that? To my knowledge of lenz's law the voltage and ...
0
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0answers
50 views

Ignoring 2nd order terms in QM definitions of translation and momentum operators

In Sakurai's 'Modern Quantum Mechanics', he defines the infinitesimal translation operator as: $\mathcal{J}(d\mathbf{x}')=1-i\mathbf{K}\cdot d\mathbf{x}'$, and then he goes on to prove this ...
1
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0answers
33 views

Does the postulate of equal a priori probability apply only to equilibrium states or to all states satisfying the constraints?

In deducing the zeroth law of thermodynamics in micro-canonical ensemble, there is a frequently-mentioned example. Suppose we put two isolated system, system 1 and 2, in contact and allowing them to ...
0
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1answer
32 views

Positive Semi-Definiteness of a Density Matrix - can the eigenvalues be larger than 1?

I know that one of the requirements for a density matrix is that it is positive-semidefinite. This means that the eigenvalues are non-negative (and sum to 1, so we can assign them the meaning of ...
2
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1answer
29 views

Integral of the parallel transport equation

The parallel transport of a vector $v_0^\alpha$ along the curve $\gamma$ is given by a vector field $v^\alpha$ which satisfies the equation $$ \frac{\mathrm d x^\mu}{\mathrm d \lambda}\frac{\partial v^...
1
vote
1answer
41 views

How do we calculate work and heat for something that is not an ideal gas?

To make learning an easier process, things are considered simple and ideal. That is great, and in the case of thermodynamics it makes calculating heat and work transfer a simple thing that is easy to ...
0
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0answers
12 views

How to calculate energy loss by eddy current?

I was reading this post: Method of calculating eddy currents of a conductor, is this correct? and I found it very interesting. They came to the conclusion that the power lost due to eddy currents was: ...
1
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3answers
85 views

Reference frames versus coordinate systems

I have the following distinction clear in my mind: Reference frame → state of motion of the observer Coordinate system → set of numbers used to map the space points within a reference frame So for ...
1
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0answers
22 views

Parallel rays hitting a parabolic mirror at an angle [on hold]

I was thinking about parallel rays hitting a mirror that has a parabolic horisontal cross-section and a linear (straight) vertical cross-section. I can't understand what would happen if the rays came ...
0
votes
1answer
28 views

Finding momentum amplitude of a wave packet when initial wave form is given

At time $t = 0$, a one-dimensional free wave packet for a particle of mass $m$ takes the form: $$ \Psi(x,0) = \begin{cases} \frac{1}{\sqrt{L}}e^{i\alpha x} & \text{for } -L/2 < x < +L/2 \\ ...
0
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0answers
28 views

What are some of the many types of string theory and other theories? [on hold]

I've been working on an essay about string theory and other theories, and would love to know some of the others that I could research. Thanks!
0
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0answers
28 views

Haar measure construction for extended Lie Algebra

Consider a Lie algebra $\mathcal{G}$ of the form $$[T_i, T_j] = f_{ij}^k T_k$$ which has an Abelian (corresponding to the Abelian Lie algebra $A$) central extension $\mathcal{H}$ of the form $$[T'_i, ...
-4
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0answers
29 views

Can a huge mass on the L1 or L2 change the earth's orbit? [on hold]

question is clear L1: Lagrange 1 point L2: Lagrange 2 point

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