0
votes
0answers
5 views

What is “a vector of $SO(n)$”?

I'm watching (or trying to watch) this lecture from NPTEL on classical field theory. I've understood everything in the series up till this point, including the first half of the lecture on elementary ...
0
votes
0answers
3 views

How can I find the magnetic vector potential of an infinite cylindrical wire

I'm struggling with an exercise that asks me to find the magnetic vector potential $\vec{A}$ inside of an infinite cylindrical wire of radius $R$ given that the current per unit area ...
0
votes
1answer
8 views

What is the cause of rolling friction? & why is it less than sliding friction?

Rolling friction is the resistance to motion experienced by a body when it rolls upon another. It is much less than sliding friction for same pair of bodies. When one body rolls upon another, there ...
-1
votes
1answer
12 views

Projecting gravity

From the title, this sounds like a question someone who is not familiar with gravity might ask. Before anyone answers or comments, I would like to say that I know gravity is a field and cannot be ...
0
votes
2answers
12 views

What makes a nucleus unstable?

My question is simply that - what makes a nucleus unstable? What exactly causes a nucleus to start breaking apart in the first place? Is it the Coulomb force between the neighboring protons? I'm just ...
0
votes
0answers
13 views

Finding the magnetic field of an infinite cylindrical wire

An infinite cylindrical wire of radius $R$carries a current per unit area $\vec{J}$ which varies with the distance from the axis as $J(s)=ks^2\hat{z}$ for $0<s<R$ and zero otherwise where k is a ...
0
votes
1answer
22 views

Newton's law of resistance

Anyone can give me some clues on how this can be proved? What kind of drag force is used? A particle is projected vertically upward with an initial speed $v_0$ near the earth's surface. Show that ...
0
votes
1answer
21 views

Cosmic Calendar [on hold]

So for an assignment I was given a event/ occurrence and was asked to find its cosmic date/ time. Here are a few examples of ones it asked for, I was wondering if there was a formula to find the date ...
0
votes
1answer
9 views

Force per unit length between two long parallel wires, one of which is insulated

Suppose we have two very long parallel wires of radius $a$ and distance between their axes $d$ ($d>>a$). The first wire if is carrying charge of linear charge density $\alpha$ and is insulated ...
1
vote
0answers
33 views

What exactly is black hole complementarity and why is it necessary for solving black hole information paradox?

What exactly is black hole complementarity and why is it necessary for solving black hole information paradox? The first question is about the story of vacuum fluctuation causing Hawking radiations. ...
0
votes
0answers
11 views

Determination of Ricci tensor and Scalar curvature from vielbeins [migrated]

Consider the following metric: $ds^2=h(r)\bigg(dr^2+r^2\big(d\theta^2+\sin^2\theta ~d\phi^2+(d\psi+\cos\theta ~d\phi)^2\big)\bigg)$ We can try to compute the Ricci scalar of this metric by using ...
1
vote
0answers
15 views

What role did the Higgs boson play in the Big Bang?

Scientists say that inflation stopped when a very peculiar energy was mobilized, did Higgs boson play any role in this? What is it's relation to the Big Bang? Some physicists, such as Michio Kaku, ...
1
vote
0answers
8 views

Validity of the static limit of a dielectric function

In general, the dielectric function $\epsilon(q,\omega)$ reflects the spatial and temporal response of a condensed matter system to an applied potential. If we put an electron into an electron sea, ...
0
votes
1answer
52 views

Can the energy of the universe ever be infinite in qunatum physics?

Suppose that the universe runs under some variants of QFT, with universal wavefunction and Hamiltonian. Then would infinite energy of the universe ever be possible? According to what I am thinking, ...
3
votes
1answer
47 views

Maxwell's Inspiration to think about fields

I was looking at a Wikipedia article which had the following statement Atomists, notably James Clerk Maxwell and Ludwig Boltzmann, applied [...]. In modern literature Maxwell is often thought ...
0
votes
0answers
20 views

Identify this radioactive-particle filter?

I am wondering if anyone can provide further info as to the preliminary principle involved in the filter shown below, any internet links would be appreciated. Is taken from a magazine related to ...
-2
votes
2answers
59 views

Why does time slow down when traveling at high speeds

One of the effects of traveling at high speeds is slowing down of clocks. I can understand gravity time dilation effect but not how would velocity affect clock speeds. How correct it is, if I say ...
0
votes
0answers
27 views

How fast time goes in zero gravity [duplicate]

I understand that the effect of gravity is warping of space because of which object travels more through space dimension and less through time dimension, this is the reason for time slowing down in ...
-1
votes
0answers
17 views

Particle moving in response to central force

So I have this question: There is a particle moving in response to a central force per unit mass of $$F(r) = {\alpha\over r^2} + {\beta\over r^3}$$ where $\alpha$ and $\beta$ are constants. ...
-2
votes
1answer
19 views

Maximum cargo that can be supported by a hot air balloon

Imagine a balloon with a volume of 3471 m^3. The density of the hot air inside the balloon is .95kgm^-3 while the density of the air is 1.2kgm^-3. What is the maximum mass of the cargo that the ...
1
vote
1answer
21 views

Does electron have angular momentum in orbital s?

I've read on science forum that electron in orbital s has no angular momentum and would fall into nucleus, so hydrogen atom would not be possible. Electron has mass and speed afterall right? So how is ...
1
vote
0answers
24 views

Home experiment with airfoils and Reynold's number

I want to do an experiment about lowering the Reynolds number of an airfoil moving through air. I want to figure out how to lower the turbulence around an airfoil. So my two hypotheses to lower the ...
0
votes
0answers
17 views

Why does U-235 split into barium and krypton in nuclear reactors?

For my chemistry project I have found the typical fission reaction which occurs in nuclear power plants is when nuclear fuel rods are bombarded with neutrons, splitting U-235 into isotopes barium and ...
0
votes
1answer
24 views

Create air stream from heat

We know that heating the air inside a bounded box raises its pressure. And if there is a hole in the box, then air flows out until the pressure inside and outside balances. So in this case we would ...
-1
votes
0answers
25 views

Physics for Scientists and Engineers by Serway Beichner solution manual [on hold]

I have found this amazing book with all possible examples that I could imagine. It is very well written and structured. I have tried to solve some problems from the Problems Sections but I can't solve ...
3
votes
2answers
66 views

Eigenstates of Spin

Why are the eigenstates of spin vectors and not functions? Is this because the spin, $s$, and magnetic quantum number, $m$, take discrete values? My textbook in an earlier section used $Y_\ell ^m$ as ...
0
votes
0answers
14 views

How to determine speed/energy of something dropped from a given height?

Say I dropped a ball from some height, which is measurable, is it possible to determine the speed of the ball when it hits the ground and thus the force exerted on the ball my the ground (or vice ...
0
votes
1answer
16 views

Will light leak into a side glow optical fiber?

I am looking into some possible applications of side glow optical fibers (plastic). Will side glow fibers "drive" adjacent fibers? That effect is undesired.
2
votes
2answers
24 views

What forces are at work in a loose ball bearing bicycle hub?

I've landed in a physics debate amongst bike mechanics. In a typical bicycle hub you have a simple bearing; the cups are set in the hub, the race (cone) threads onto the axel and there are just loose ...
0
votes
3answers
48 views

Proper way to write the units to indicate that they include an offset?

Past a certain point of complexity, I get rather confused with physical units, so I am asking a physicist for help. I have a code that represents temperature, with a resolution of [0.5 °C], whose ...
0
votes
1answer
21 views

Calculating distance between two objects viewed from an angle [on hold]

I'm trying to determine the location of this vehicles rear bumper and the front edge of the white road marker. I can't tell if the vehicle is before, at the edge, or just ahead of the marker. The ...
1
vote
1answer
20 views

The spin and weight of a primary field in CFT

A primary field in Conformal Field Theory transforms as $$\phi (z,\bar{z}) =\left(\frac{dz}{dz'} \right)^h \left(\frac{d\bar{z}}{d\bar{z}'} \right)^\bar{h}\phi (z',\bar{z}') $$ under a conformal ...
-3
votes
2answers
27 views

If infinite amount of different strong particles were to be confined and jammed together, what would occur? [on hold]

Consider this scenario; If an infinite amount of neutrinos, electrons, positrons, and photons of enormous wavelengths were to be confined, concentrated or jammed together in a relatively large space ...
0
votes
0answers
17 views

Does the Schrodinger equation with Yang-Mills potentials really arise in some gauge theory?

In many mathematical papers one calls the equation $$ \sum_{j=1}^n \biggl(\frac 1 i \frac{\partial}{\partial x^j}+A_j(x) \biggr)^2 \psi + V(x)\psi = E\psi, $$ where $A_j(x)$, $V(x) \in M_n(\mathbb ...
1
vote
2answers
36 views

How does air in a water balloon act in space?

I was making an analogy with gravity and water and it went like this. When air is trapped in water as a bubble, water is pushing towards the inside and like Newton's law equal and negative forces ...
1
vote
1answer
13 views

Uncertainty of approximately sinusoidal voltage measurement

Say one is interested in measuring the mean value an approximately sinusoidal voltage with an instrument that has an accuracy of 0.01 V, according to its spec sheet. 10 periods of the oscillation have ...
0
votes
0answers
9 views

Elasticity of a body on which variable force is applied

Let us consider a rod of some cross sectional area A and length l.At one end a longitudinal foce of 5x acts on the rod. At a distance of l/2 from that point longitudinal force of 5x acts on the rod ...
2
votes
0answers
30 views

Why is only the third component of weak isospin used as conserved quantity?

Using Noether's theorem \begin{equation} \partial_0 \int d^3x \left(\frac{\partial L}{\partial(\partial_0\Psi)} \delta \Psi \right) = 0 \end{equation} we get three conserved quantites $Q_i$ from ...
1
vote
0answers
18 views

Calculating the age of the Universe at temperature 1 MeV [duplicate]

I've been told calculate the age of the Universe at $T = 1 \, \text{MeV}$, assuming that $a(t=0)=0$. Now, I've already calculated the value of $H$ at that temperature, which was around ...
3
votes
1answer
28 views

The contribution to the one loop beta function for the WZW model

When the Wess-Zumino-Witten model $$S_{WZW}=\frac{k}{4\pi}\int d^2 z \, \, \mathrm{Tr}[\partial u \bar{\partial}u^{-1} ]+ \frac{k}{12\pi}\int d^3 \sigma \epsilon^{ijk}\, ...
9
votes
4answers
1k views

Does screwdriver length matter?

Everyone who deals with screws and screwdrivers knows that long screwdrivers are stronger than short ones. However, I can't find any relationship between length of a screwdriver and mechanical ...
0
votes
2answers
35 views

Does the work function of metal depend upon the intensity of light?

does work function of metal depend upon the intensity of light?or does it depend upon the nature of metal?And according to my perception its depend upon both intensity and nature of light.
0
votes
0answers
19 views

Space Between Current universe and point of origin [duplicate]

If universe is expanding like a balloon from point zero to current space time. what is there in between the point of origin and current universe. Is there still hot energy in between the current ...
2
votes
0answers
54 views

Which field of theoretical physics is most promising? [on hold]

I'm about to choose university and I really love physics, but I don't know about use of it. What field is most promising to study? Where could I work with subatomic particles PhD? Or maybe nuclear ...
1
vote
0answers
51 views

Is there really such a thing as a left-chiral particle?

A chiral eigenstate is always a linear combination of a particle and an antiparticle state and a particle or antiparticle state is always a linear combination of chiral eigenstates. Now, how can we ...
0
votes
0answers
31 views

Stability of a system

What do we mean by "stability of a system " in a Lagrangian of a model? Let's say that we have a very simple model like this $$L=\frac{1}{2}K_{ij}\dot{q}_i\dot{q}_j-\frac{1}{2}F_{ij}q_iq_j,$$ where ...
1
vote
3answers
50 views

How are the half life of particles mathematically related to the inverse square laws?

This video https://www.youtube.com/watch?v=K6i-qE8AigE&list=PL3B0924C6A0CB8B67 explains how forces are boson particles. It talks about the other non-force particles giving off and creating bosons, ...
4
votes
1answer
22 views

Calculating the angular power spectrum of a section of sky

To calculate the angular power spectrum $C_l$ of the whole sky, one uses the variance of the coefficients of the spherical harmonics in the temperature fluctuation field. I.e. $$C_l = ...
1
vote
0answers
45 views

BRST quantization of point particle

Suppose we have Lie algebra $\mathfrak{g}$ with basis $t_a$ with a representation $$ t_a \mapsto K_a: V \to V. $$ Denote by $c^a$ the dual basis. Chevalley differential is defined as $$ Q = c^i K_i - ...
1
vote
2answers
32 views

Would using a fan cause an air conditioning system to think it's cold?

Recently my office manager said this, after I requested a desk fan: ...using a fan causes a draught, which then leads the air conditioning to believe it’s cooler than it is and it then blows out ...

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