0
votes
0answers
2 views

Given state cannot be written as a linear combination of pure states

Ok. This is just a numerical example to be better understood. If I am given a state let's say (1,1,0) of a H matrix let say ((3.2.0),(2,0,0),(0,0,1)), since the initial state cannot be written as a ...
0
votes
0answers
7 views

Kinematics - Projectile Motion problem, projectile lands at an angle

Question: You are watching an archery tournament when you start wondering how fast an arrow is shot from the bow. Remembering your physics, you ask one of the archers to shoot an arrow parallel to the ...
0
votes
0answers
11 views

Kähler Potential of Calabi-Yau volume

At tree level, the Kähler potential is given by (neglecting complex structure) $K = -\ln(-\mathrm{i}(\tau - \bar{\tau})) - 2\ln(V_{CY})$ where $V_{CY} = \frac{1}{6} \kappa_{abc}t^at^bt^c$ ia the the ...
-3
votes
2answers
16 views

Can the mass of a body change under any condition or not?

We know that mass can neither be changed nor be destroyed, but I want to know if there is any circumstance under which the mass of a body can be changed?
-1
votes
0answers
11 views

From what time does we humans are knowing about charge?

We know that the electron is discovered in 1897 by JJ Thomson. So the knowledge about charge, current, electricity and all those terms related to it which we study today are discovered after it or the ...
0
votes
0answers
9 views

Functions of the form $F(x-ct)$ written as superposition?

In this section of the Wikipedia article on the wave equation they do the following: $$\int^{\infty}_{-\infty}s_+(\omega)e^{-i(kx+\omega t)}d\omega +\int^{\infty}_{-\infty}s_-(\omega)e^{i(kx-\omega ...
0
votes
0answers
6 views

Q: Any standard terminology for “gold standard” Monte Carlo solutions

The "standard" way in our field to compute scattering statistics in wave propagation problems is via a "deterministic" wave prop code operating in a Monte Carlo context where we iterate over many ...
0
votes
1answer
7 views

Why the electrons flow from higher potential to lower potential?

We know that every thing moves from a higher potential to lower potential. In fact we also studied in our textbooks that a charge travels from higher potential ie. Positive side to lower potential ie. ...
-1
votes
0answers
10 views

Incline plane problem

A string carrying a $5\times10^{-2}$kg bob hangs from the roof of a vehicle. It moves down an incline at an angle of $30 °$ with the horizontal with acceleration of $3\mathrm{ms}^{-2}$. What angle ...
0
votes
1answer
7 views

How can we know that a particular charge is positive or negative?

Suppose I am provided with a positive is charged....and someone tells me to find which type of charge is present in it? Then how can we detect that the body is positively or negatively charged? Is ...
0
votes
1answer
13 views

Is electric current a scalar quantity?

According to the definition of a Scalar quantity that i have read in class 9 is that ''those quantities which has only magnitude but no direction is known as a scalar quantity''.....But in class 10 i ...
0
votes
1answer
17 views

Connections between Density Matrix Renormalization Group and Conformal Field Theory

Can we use the density matrix renormalization group (DMRG) method to understand problems in conformal field theory? I have been trying to find some connections, but nothing is coming up when I search. ...
0
votes
0answers
8 views

Does the weak force obey a symmtery/conservation law that is broken by the EM and strong forces?

It always seems that the weak force breaks everything that is otherwise obeyed by the other fundamental forces, but there something that only the weak force is known to follow?
0
votes
0answers
10 views

Unanswered Questions in Quantum Phase Transitions

What are some of the biggest unanswered questions/unexplored areas in the study of theoretical quantum phase transitions? In particular, how are people using the AdS/CFT correspondence to understand ...
1
vote
0answers
15 views

Problem with energy bands

I am getting confused by the energy bands. As far as I know, the outermost shell of an atom is called valence shell. The electrons residing in that shell participate in reactions and conduction of ...
-1
votes
0answers
28 views

Where does this hyperbolic tangent in Nakahara's text come from?

I don't see why the term with $\tanh$ appears in the equation 1.164 The textbook is the second edition of Geometry, Topology and Physics
-3
votes
0answers
8 views

How to find the enthalpy if I have the pressure and temperature?

There is a refrigerator with R-134a as the working fluid. The R134a enter the evaporator at P=100kPa, quality =0.2 and it leaves at P=100kPa, T=-26 degree Celsius How can I find out the enthalpy? I ...
0
votes
3answers
26 views

why does a ball roll

I searched for my question and I found many results but all of them eventually try to solve something specific (like solving for the kinetic energy or finding when does the ball stop). what I want ...
1
vote
0answers
15 views

Why are the azimuthal quantum number $\ell$ and magnetic quantum number $m$ integers?

Why are the azimuthal quantum number $\ell$ and magnetic quantum number $m$ integers?
0
votes
0answers
28 views

The Lie algebra of the Lorentz group is $su(2) \oplus su(2)$. Is there a similar relation for the algebra of the Poincare group?

It can be shown easily, by introducing new generators from the usual ones that we can think of the Lie algebra of the Lorentz group as being built up by two copies of the $SU(2)$ Lie algebra: $$ ...
-1
votes
0answers
16 views

Movement of accelerating points with maximum speed (i.e. running away from tiger)

I'm walking through forrest and suddenly I see a tiger. And now I have a problem. I want to know how much time I have left but I don't know how to calculate it. Or more fomally: Let's say there are ...
2
votes
2answers
20 views

How do we know that the cesium-beam frequency used in atomic clocks is always the same?

Atomic clocks use cesium-beam frequency to determine the length of a second. This has shown that the period of orbit of the earth is decreasing. But what experiment showed that cesium-beam's period ...
0
votes
3answers
30 views

Work and energy

when a ball of mass m is brought with uniform velocity from infinity into the g field of the earth at a distance r from it, the potential energy of the ball earth system decreases from 0 to -GMm/r. ...
1
vote
1answer
18 views

How to calculate Electric Field near a charged conducting surface without Gauss' law?

I have two problems : In every textbook I find the use of Gauss' law in calculation of Electric Field near a charged conducting surface. Can it be calculated without Gauss' law? Suppose while using ...
-1
votes
0answers
28 views

Unitary evolution operator

Assume we have a system in a state $\psi$ that is a superposition of eigenvectors of some observable $A$. Now we make a measurement of the observable $A$; the state after the measurement $\phi$ is a ...
0
votes
0answers
27 views

The general equation for a wave packet derivation?

On Wikipedia it gives the general equation for a wave packet (and therefore for a wave?) to be: $$u(x,t)=\frac{1}{\sqrt{2\pi}}\int^{\infty}_{-\infty}A(k)e^{i(kx-\omega t)} dk$$ I have been trying to ...
1
vote
0answers
11 views

Calculating Time to reach a given velocity knowing force of thrust

so I am working on a physics problem for a class I am taking. The problem is as follows: -A rocket, weighing $4.36\times10^4 N$ has an engine that provides an upward force of $8.90*10^5 N$. It reaches ...
1
vote
1answer
30 views

Time dependent Hamiltonian and Gauge invariance

In general, in quantum mechanics we can prove probability current or the Schrodinger equation and other quantities are gauge invariant. However, the Hamiltonian isn't gauge invariant. Under a gauge ...
0
votes
0answers
20 views

Angular momentum of light in classical electrodynamis [on hold]

I' reading at this time electrodynamics from Griffith's Introduction to electrodynamics. As i see, to have the conservation laws in field theory we have to consider the fields as carrying energy, ...
1
vote
3answers
102 views

Object moving in a circular path without accelerating

A train is moving with a constant speed on a straight portion of track. Then, it encounters a curve in the tracks, and goes along the curve. However, it does not accelerate during its time on the ...
0
votes
1answer
54 views

Does elementary particle emit photon?

Charged particles are accelerated by the magnetic field in a particle collider before allowed to smash together at specific location where the detectors are housed. My question is do the ...
0
votes
0answers
14 views

Construction of free energy based on Landau theory

Consider an Ising model system where the total energy is $E = −J \sum_{<ij>} S_iS_j $, $S_i = \pm 1$ and $< ij >$ implies sum over nearest neighbours. For $J < 0$ the ground state of ...
-3
votes
0answers
32 views

Jee Main 2015 Question. Inter-molecular Interaction [on hold]

The Intermolecular interaction that is dependent on the inverse cube of distance between the molecules is: Hydrogen Bond? ion-ion interaction? ion-dipole interaction? London Force?
1
vote
2answers
90 views

Number of microstates compatible with two boxes

From my notes I have: From one point of view there are many more microstates compatible with the LHS than the RHS, in fact the relation between the number of microstates is ...
-2
votes
0answers
70 views

JEE MAIN 2015 Question. Electromagnetism [on hold]

Two coaxial solenoids of different radii carry current I in the same direction. Let F1 be the magnetic force on the inner solenoid due to the outer one and F2 be the magnetic force on the outer ...
1
vote
1answer
32 views

Understanding the behavior of light/photons inside a Laser

I am trying to establish a model inside my head of how light behaves but find it hard with all the seemingly contradicting information. For example, electrons inside a Laser are raised to a higher ...
-3
votes
0answers
19 views

Why does internal energy remains constant in isothermal system? [on hold]

how to write this answer for 2 marks question simple and straight answer. Please
2
votes
2answers
39 views

Neutron star: free fall acceleration

The textbook from which I teach physics at the end of secondary school, has a question about a neutron star: $M_{star}=1.4\cdot M_{sun}$, radius 15km. "Calculate the free fall acceleration at the ...
2
votes
0answers
31 views

Is $SU(2)$ really broken by the Higgs VEV or just hidden?

It's generally stated in the textbooks that whent the Higgs field acquires a certain vev the corresponding symmetry is spontaneously broken. For example in A. Zee - QFT in a Nutshell: But none of ...
2
votes
1answer
18 views

How to calculate earth's magnetic field by time period of suspended magnet?

Assuming that torsion of the suspension wire small enough to be neglected, how can we derive earth's magnetic field by measuring time period of an oscillating magnet suspended on a string?
0
votes
2answers
37 views

Ice at zero gravity

I wish to know the behavior of ice at zero gravity, sound at zero gravity. How ice will behave when melted and how sound will break a closed glass at zero gravity vs g on earth? Thanks
0
votes
0answers
26 views

Infinite force between two point charges as $r$ approaches 0 [duplicate]

According to coulombs law the Force experienced by two point charges increases with the inverse square of their separation. This would imply that at distances approaching 0, the Force approaches ...
1
vote
2answers
34 views

Energy conversion (conceptual) question

Suppose I have a electronic car. It runs by electrical energy. So when wheels rotate, mechanical energy is produced. Then why can't we convert it back to electric energy and produce somewhat unlimited ...
0
votes
2answers
91 views

Why do termite pellets fall in a perfect circle?

I was just wondering why termite pellets fall down from my bed in a perfect circle. You can see from the images that the follow down on the floor making a perfect geometric figure which is void in ...
1
vote
0answers
36 views

Could there be a function or property having non-linear mass dependence? [on hold]

I'd like to know some properties or functions that possess a *non-*linear relationship with mass. For example: a property like $ x = T m^n$ I am interested particularly in classical newtonian ...
13
votes
6answers
830 views

Does gravity exist in a vacuum?

My understanding has always been that it does from conventional science courses, but really thinking about it, I was wondering if this is really the case. To my limited understanding there is a ...
1
vote
0answers
7 views

Whether phase congruency and phase coherence terms are same or different?

I am studying the importance of phase in signal.Can anybody explain what is phase congruency ? Also,I am confused between terms i.e. phase congruency and phase coherence. Whether phase congruency and ...
0
votes
1answer
19 views

Ohmic and non-ohmic conductors

What sort of materials are ohmic and what sort of materials are non-ohmic? I have tried looking around on the internet and have not found any clear way to differentiate between ohmic and non-ohmic ...
0
votes
1answer
41 views

Perturbations in linear response theory

I've been working on applications of linear response theory to condensed matter systems, and I've got quite far into the literature on the subject. However, there is an identity which seems to be ...
0
votes
1answer
33 views

Do/May pure electromagnetic waves ( Non dual natured ) exist?

The light as well as all matter 'particles' show dual nature. But my question is if according to the Maxwell equations, Electromagnetic waves are valid events, can they actually exist in pure wave ...

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