1
vote
2answers
129 views

Can acceleration feel like constant gravity for indefinitely long?

So here's the setup: I'm in a spaceship, without windows as always, and the ship is accelerating upwards at a constant rate of $1\,\text{g}$. So inside the spaceship it feels like I'm being pulled ...
3
votes
3answers
3k views

Why the direction of dipole moment is from negative charge to positive charge?

An electric dipole moment is defined as $p = q\times 2d$. How to understand it physically? Why the direction of the electric dipole moment is from negative charge to positive charge?
3
votes
2answers
918 views

Is there any example where electric and magnetic fields are not perpendicular?

Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
1
vote
2answers
380 views

Utilizing maximum acceleration $a$ for displacement $d$ with initial velocity $v_0$ and final velocity $v_1$

Problem My goal is to move an object from point a to b (displacement $d$) as fast as possible utilizing the maximum available acceleration $a_{max}$, taking into account the initial velocity $v_0$ ...
1
vote
0answers
90 views

Sommerfeld results & van Hove singularities

According to Sommerfeld the derivative of the density of states $g'(\varepsilon)$ apears in several thermodynamic quantities. Will this also be the case if one use the correct dispersion relation of ...
1
vote
1answer
249 views

Force required to move a fluid out of piston at depth

I have a cylinder filled with water in it at the bottom of the ocean. Say 100 meters down. In this cylinder is a piston that moves up and down. Its job is to squish the water out the bottom of the ...
3
votes
0answers
90 views

What is the fundamental difference between ghost and auxiliary fields?

I am somehow confused by the notion of auxiliary fields, such as for example the fields F and D which appear in supersymmetry, and the notion of ghost fields which appear for example in the BRST ...
5
votes
1answer
131 views

Strange Grassmann double integration

I can unterstand why because the integration over Grassman variables has to be translational invariant too, one has $$ \int d\theta = 0 $$ and $$ \int d\theta \theta = 1 $$ but I dont see where ...
0
votes
1answer
48 views

About electrostatic potential energy

I consider an electron (charge $-e$) in $x=0$ and a constant electric field $E(x) \equiv E $. If the electron has initial velocity $v_0$ with the same direction of $E$, then its potential energy is $$ ...
0
votes
0answers
27 views

What is the principle of active voltage balancing/equalizing device?

I am wondering about active voltage sharing devices. Their purpose is to equally divide voltages on slightly unequal super-capacitors. I found some papers like this, but it is too scientific. I want ...
4
votes
2answers
127 views

quantization of angular momentum

What is the most direct way of observation of quantization of angular momentum?
5
votes
1answer
305 views

Vector and Spinor Representation in Ramond-Neveu-Schwarz Superstring Theory

I am learning Ramnond-Neveu-Schwarz Superstring theory (RNS theory). I often find the following notation, especially in the closed string spectrum etc.: $$\mathbf{8}_s,\mathbf{8}_v $$ And it is ...
0
votes
2answers
208 views

What's the motion of this yoyo under external force will be?

A yoyo on a horizontal table is being pulled by a string to the right, the table is not frictionless. If we only know that the object doesn't slip, how do we know if the string is winding up or ...
2
votes
3answers
914 views

If photons can be absorbed by electrons, wouldn't that mean light has a charge? [duplicate]

I am a biochemistry and molecular biology major. If photons can be absorbed by electrons, wouldn't that mean light has a charge? Electrons only attract positive charges. Isn't it?
7
votes
0answers
90 views

Does quark color contribute to “spin degeneracy” for QGP calculations?

Like the title say, does quark color matter in counting contributions in a early universe plasma (QGP), as when adding up the total plasma energy density, or is it just spin? The book I have (Pathria) ...
2
votes
0answers
30 views

How to write down the detailed balance (microreversed) amplitude

I know that time-reversal of a reaction and the detailed balance (microreversed, or reciprocal) reaction are different. Textbooks on scattering theory explain how to relate the S-matrix elements of a ...
1
vote
0answers
34 views

Information-theoretic limits in observational astronomy

It seems to me that with ever larger and better telescopes and powerful statistical methods, humans are gleaning surprising amounts of information from observations of distant stars. I am especially ...
4
votes
1answer
196 views

QM with complex eigenvalues

What class of theories/physical systems own finite/infinite complex eigenvalues? I do know that e.g., quasinormal modes of BH do have complex eigenvalues, but are they finite or infinite in number? ...
0
votes
1answer
160 views

Solving the soliton equation without energy

In this passage from Srednicki's Quantum Field Theory (page 576) The solution of interest is time independent, so we can set $\dot\varphi = 0$. We can also rewrite the remaining terms in $E$ as ...
3
votes
1answer
93 views

For how long must a molecule remain stable to be considered “stable”?

In the Star Trek: Voyager episode The Omega Directive, Seven of Nine says that the Borg synthesized a molecule which was "kept [] stable for one trillionth of a nanosecond before it destabilized". ...
0
votes
0answers
160 views

Quantum uncertainty can explain the Riemann Hypothesis?

In the recent paper "Riemann Hypothesis as an Uncertainty Relation" (http://arxiv.org/abs/1304.2435) the author claims that the presence of zeros out of the critical line may lead to the violation of ...
5
votes
2answers
621 views

What is the largest sphere of liquid water that could exist in space held together under it's own gravity? [duplicate]

What is the largest theoretical sphere of liquid water that could exist in space held together under it's own gravity? I've always wondered if a planet the size of earth could exist as a single volume ...
4
votes
2answers
435 views

Graphene +1 extra carbon bond

I'm not a physicist just a curious mind, so please go easy! I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
2
votes
1answer
137 views

How to find the Higgs coupling with a mixing matrix?

It is known that the couplings to the Higgs are proportional to the mass for fermions; $$g_{hff}=\frac{M_f}{v}$$ where $v$ is the VEV of the Higgs field. I'm trying to figure out why this is true ...
3
votes
1answer
115 views

Transformation law for fermionic measure in functional integral

I am reading the paper "Bosonization in a Two-Dimensional Riemann-Cartan Geometry", Il Nuovo Cimento B Series 11 11 Marzo 1987, Volume 98, Issue 1, pp 25-36, ...
0
votes
0answers
55 views

Partial Measure Probability

Let be a $$|\psi\rangle = \dfrac{3}{5\sqrt{2}}|00 \rangle- \dfrac{3i}{5\sqrt{2}}|01 \rangle+ \dfrac{2\sqrt{2}}{5}|10 \rangle - \dfrac{2\sqrt{2} i}{5}|11 \rangle$$ state with two qubits. ...
1
vote
1answer
130 views

The Klein–Gordon equation

As we know that the Schrödinger equation presents basis of Quantum Mechanics and analogy with Newton second law in Classical Mechanics, I thought that relativistic interpretation of Schrödinger ...
0
votes
1answer
546 views

Phase shift of resonance [duplicate]

For resonance to occur, is it true that the force lags behind the motion by $\pi/2$? I saw some notes written that the motion lags behind the force by $\pi/2$ which makes no sense to me. As I watched ...
1
vote
1answer
155 views

What is paramagnetic current-current correlation?

I know what paramagnetism is. But first I want to know about the paramagnetic current and then the above-mentioned correlation? Actually, I am working on a paper on superconductivity where I have ...
1
vote
0answers
25 views

Magnetic field-pulsed microwave transmission line

Here's the reference: The researchers showed that a magnetic field-pulsed microwave transmission line containing an array of superconducting quantum interference devices, or SQUIDs, not only ...
3
votes
1answer
183 views

The issue on existence of inverse operations of $a$ and $a^{\dagger}$

I have asked a question at math.stackexchange that have a physical meaning. My assumption: Suppose $a$ and $a^\dagger$ is Hermitian adjoint operators and $[a,a^\dagger]=1$. I want to prove that ...
1
vote
1answer
92 views

Mysterious spectra?

In my blog post Why riemannium? , I introduced the following idea. The infinite potential well in quantum mechanics, the harmonic oscillator and the Kepler (hygrogen-like) problem have energy spectra, ...
1
vote
1answer
76 views

What happens to the $2\pi$ factor when calculating Raman-shifts in units of wavenumbers?

So from the classical theory, you find a formula for a dipole in a planar electromagnetic wave, where there will be two cosine terms with a frequency (actually angular velocity in $[rad/s]$, as the ...
3
votes
2answers
149 views

Friction on roads

I have a question with which I am having trouble. A 71m radius curve is banked for a design speed of 91km/h. Given a coefficient of static friction of 0.32, what is the range of speeds in which a car ...
1
vote
0answers
82 views

What temperatures can be reached in an air-to-air thermocompressor nozzle and why?

People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
2
votes
1answer
988 views

Find temperature of surface (Blackbody Radiation)

An astronomer is trying to estimate the surface temperature of a star with a radius of $5 \times 10^8\ m$ by modeling it as an ideal blackbody. The astronomer has measured the intensity of ...
2
votes
1answer
737 views

Does gravity affects temperature reading of a mercury thermometer?

I remember when I was in primary school, the science teacher put me in charge of a mercury thermometer. I do not quite understand the mechanics behind except that mercury expands when it is hot and ...
6
votes
0answers
110 views

How can dynamics be reversible if inflation-style baby universe spawning is allowed?

I just finished readying Sean Carroll's book, "From Eternity to Here", and have a question about reversibility and inflation: Assume inflation allows random quantum fluctuations to produce high ...
3
votes
1answer
97 views

How do I calculate how something should stay in position under gravity?

Excuse me if this too simple a question - I'm not a regular (consciously) user of physics. I have a ship in space and it is under the effect of three moons. The ship can rotate and thrust to move ...
1
vote
1answer
169 views

what's the center of mass for triatomic-molecule system

My text use the following example to explain the center of mass. There are three balls (mass $m$) sitting in the origin, at $x=l$ and $x=2l$, each two mass are connected with a spring of constant $k$. ...
8
votes
0answers
156 views

Is it believed that all UV completions have “Maldacena duals”?

I have heard occasional rumors that effective field theories have gravity duals. For example, I've been told that UV momentum cutoffs in N=4 SYM become finite radii in AdS. I've heard speculations ...
3
votes
1answer
113 views

How can the derivative of this trace be constrained?

I am studying for my exam on relativity and I am going through some problems sets including ones where I was not very successful in so I want to know how to do this problem. (Convergence of ...
1
vote
2answers
127 views

Suggestions on a particular arXiv publication on math needed for theoretical physicists [closed]

I'm going to start my PhD in a year and I'll be taking a gap year doing other stuff. But I also wanted to fill in the gaps in my math knowledge and I came across an arXiv publication called ...
2
votes
1answer
188 views

How to calculate beam spread of a non-point light source via an aspheric lens

I need to determine the angle, or rate of divergence of light from a single aspheric lens when I place a non-point light source (e.g. LED array) at a given distance from the lens which is less than ...
2
votes
1answer
121 views

At the smallest level, how do things move?

When we see something moving on a screen it's usually just pixels being turned off at one location and turned on at another. For example: This would render a dot moving from A to C. Turn on pixel ...
1
vote
2answers
101 views

Does spatial coupling prohibit resonances due to an external source field?

The harmonic oscillator coupled to a sinodial external source $$\tfrac{\partial^2 x(t)}{\partial t^2}+\omega_0^2 x(t)=F_0\sin(\omega_\text{ext}\ t),$$ has the solution $$x(t)=x(0)\cos(\omega_0 t)+C ...
-1
votes
1answer
386 views

Has anyone on Earth ever seen the dark side of the moon and if so where are the pictures? [duplicate]

If the Moon rotates then we should see the dark side right? But as far as I know the Moon only shows one side to Earth, how can this be if it is rotating?
0
votes
1answer
125 views

Electromagnet, ideal turns depending on ohm

More turns -> stronger field more turns -> longer copper wire longer copper wire -> more resistance(ohm) at what turn does the resistance make the electromagnet weaker? - I want to make an ideal ...
3
votes
1answer
129 views

Units for physical constants

Someone told me that units for $G$ and $\epsilon_0$ (gravitational constant and Coulomb's constant) are placed there simply to make equations work dimensionally and that there is no real physical ...
2
votes
0answers
132 views

About the seesaw mechanism

I was reading about the seesaw mechanism in my Lecture notes and got a technical question. See for example http://www.lhep.unibe.ch/img/lectureslides/9_2007-11-30_SeeSawMechanism.pdf page 13. There ...

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