All Questions
12,536 questions
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What exactly is the definition of motion and its relation to Mach's conjecture?
The notion of "movement" seems to be well understood in physics. In fact, I don't recall any physics text-book defining motion. Special relativity theory says that there is no absolute frame of ...
- 3,443
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3
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4k
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Are Classical Field Theory and Quantum Mechanics of a single particle (nonrelativistic or "classical") limits of Quantum Field Theory?
Recently I talked about QFT with another physicist and mentioned that the Quantum Field Theory of a fermion is a quantisation of its one-particle quantum mechanical theory. He denied this and ...
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3
votes
1
answer
272
views
Does decoherence single out a preferred frame?
Environmentally induced decoherence makes wave function collapse unnecessary. But the environment, usually taken to be some heat bath, introduces a preferred frame. (That in which the total (spatial) ...
- 5,765
1
vote
0
answers
151
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Einstein's postulates <==> Minkowski space. In layman's terms [duplicate]
Possible Duplicate:
Einstein's postulates <==> Minkowski space. (In layman's terms)
In the spirit of Einstein's arguments using flashes of light, moving trains and mirrors;
what is ...
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4
votes
1
answer
664
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Commutation of operators in quantum theory
I have always written the commutation rules of quantum theory as ,
$[q,p] = i\hbar\delta _{ij}$
But seems that some people write this as,
$[q^i,v_j]= \frac{i\hbar}{M}\delta^i _{j}$
(..this is ...
- 181k
2
votes
1
answer
812
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whats the rate of energy increase required for constant acceleration between 0.0c and 0.99c?
I was wondering how much energy would be required to accelerate 1000kg to 0.99c at 1G.
What I don't understand is what the rate of increase of energy is required as velocity increases. I was looking ...
- 77.3k
4
votes
2
answers
930
views
Non-interchangeability of time-like intervals
I am reading Landau's Volume 2 of the course of theoretical physics. I have a doubt after reading the first few pages of it which I explain below.
Landau first defines intervals and on pages 5 and 6 ...
- 20.1k
8
votes
2
answers
2k
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Nature of spacetime 4-vector and tangent space?
An entry level confusion about spacetime. I understand that a 4-vector describes a point or event in spacetime. But I've also read (Bertschinger, 1999) that re spacetime "we are discussing tangent ...
- 5,305
1
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0
answers
139
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heliocentricity and the theory of relativity [duplicate]
Possible Duplicate:
Why do we say that the earth moves around the sun?
I should preface by stating that I'm not a physicist and my knowledge of the theory of relativity is limited to what Encarta ...
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1
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3
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324
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How is energy conserved when a moving charge has false ideas about positions of other charges
An electron is shot towards a target that is negatively charged. While the electron is traveling, the target makes an abrupt move towards the electron. While the information that the target moved is ...
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5
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1
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653
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Length contraction in rotating frame?
If an observer were to rotate around a point at near light speeds, what sort of length contraction would he observe the universe undergo?
- 13k
2
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1
answer
412
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Does a light cone look the same from all reference frames?
If there were a light cone centered at some point $P$, and you were to look at that light cone from different reference frames, would it change its shape? I know that points inside and outside the ...
- 53.7k
2
votes
2
answers
1k
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Why is travelling around the speed of light a problem?
I don't fully understand what would happen if we could travel at the speed of light. But I saw somewhere here that it would mean events happen out of order. But why is this a problem. It is said that ...
- 181k
4
votes
2
answers
362
views
Special Relativity and time [duplicate]
Possible Duplicate:
Question about Time Dilation..
I have a question about special relativity which was bothering me for a while now. I know that as one approaches the speed of light, time moves ...
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2
votes
1
answer
505
views
Physical interpretation of equation for relativistic aberration
I'm working in a book on relativity. The author states that if $u$ and $u'$ are a velocity referred to two inertial frames with relative velocity $v$ confined to the $x$ axis, then the quantities $...
- 388
2
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1
answer
275
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A video conference between earth and a space shuttle
I have just started looking into special relativity and I have come up with an intriguing gedanke, as Einstein himself called such theoretical thought experiments.
Imagine a space shuttle traveling ...
- 20.1k
5
votes
1
answer
1k
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How to mathematically formulate the Two Slit Experiment in Special Relativity?
How to mathematically formulate the Two Slit Experiment in a Lorentz invariant framework.
Is there a paper about this?
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1
vote
1
answer
708
views
Does change of coordinate system require acceleration?
This question came about from a side discussion that arose on this:
Does GR provide a maximum electric field limit?
Can we change our choice of coordinate system completely independent of physical ...
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9
votes
1
answer
688
views
Is there a rest frame for the Higgs boson?
If there is a non-zero expectation value for the Higgs boson even in "vacuum", since the Higgs boson has a mass unlike photons, then I would expect it to have a rest frame.
So why doesn't a non-zero ...
- 181k
2
votes
2
answers
3k
views
What is the effect of temperature on electrostatic-gravitational balance?
We have two identical massive metal spheres at the same temperature at rest in free space. Both have an identical charge and the Coulomb force [plus the black-body radiation pressure if the ...
- 478
5
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3
answers
853
views
Paradoxical interaction between a massive charged sphere and a point charge
Suppose we have a sphere of radius $r$ and mass m and a negatively charged
test particle at distance d from its center, $d\gg r$. If the sphere is electrically neutral, the particle will fall toward ...
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3
votes
1
answer
2k
views
What is the exponential form gamma matrix for a general rotation and boost?
It would be nice to have a cute method that uses Lorentz transformations of basis vectors by exponential transformation using gamma matrices. To avoid confusion, let's assume -+++ signature. Given $\...
- 181k
3
votes
1
answer
6k
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Relativistic charged particles in a constant uniform magnetic field
How can i derive the dynamic of a relativistic charged particle in a uniform magnetic field $B=(0,0,B)$?
- 3,302
2
votes
1
answer
565
views
How much energy can be extracted from hydrogen?
http://en.wikipedia.org/wiki/B-L says that the difference between baryon number and lepton number is conserved. Ordinary hydrogen has one of each, but turning it into helium releases only the binding ...
- 13k
3
votes
2
answers
181
views
Knotted token-ring network
Suppose we have a rigid token-ring network. An observer at any node can seemingly determine the angular momentum of the network by measuring the time it takes for a packet to travel around the ring ...
- 13k
7
votes
4
answers
3k
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Why are four-vectors needed in the Dirac equation, when there are 4 linearly independent 2D matrices?
I was taught that for the Dirac-equation to "work", you need matrices of the following form:
$Tr(\alpha^i) = 0$.
Eigenvalues +1 or -1
2 previous points together: equal number of negative and positive ...
- 4,763
2
votes
1
answer
2k
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Magnetic moment of relativistic rotating ring
Let's consider rotating charged ring. Theoretically mass of this ring has no limit as rotation speed increases. So what about magnetic moment of the ring? Is it limited by the value of speed of light?...
- 2,094
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3
answers
2k
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Is there a relativistic (quantum) thermodynamics?
Does a relativistic version of quantum thermodynamics exist? I.e. in a non-inertial frame of reference, can I, an external observer, calculate quantities like magnetisation within the non-inertial ...
- 9,966
7
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3
answers
1k
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twistor-spacetime correspondence
Could someone explain the correspondence between lines in twistor space and minkowski space-time points? a basic derivation would suffice
- 4,763
5
votes
2
answers
2k
views
If the light velocity is a vector quantity, why vector addition cannot be applied to it?
If the light velocity is a vector quantity, why vector addition cannot be applied to it?
Or the light velocity is not a vector quantity?
- 11.3k
1
vote
2
answers
862
views
What kind of invariants are proper time and proper length?
Under the Lorentz transformations, quantities are classed as four-vectors, Lorentz scalars etc depending upon how their measurement in one coordinate system transforms as a measurement in another ...
- 181k
5
votes
3
answers
850
views
Time Dilation - what happens when you bring the observers back together?
I'm having trouble getting my head around the time dilation paradox.
Observer A and B are at the same "depth" in a gravity well. Observer B then descends into the well. A will observe B's time as ...
- 176
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2
answers
2k
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Is there an intuitive geometric view of the effects of Lorentz transformations?
Is there a time + two spatial dimension representation of a Minkowski-space surface which could be constructed within our own (assumed Euclidean) 3D space such that geometric movement within the ...
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2
votes
1
answer
650
views
Pulsar gravitational binding energy?
A Newtonian homogeneous density sphere has gravitational binding energy in Joules $U = -(3/5)(GM^2)/r$, G=Newton's constant, M=gravitational mass, r=radius, mks. The fraction of binding energy to ...
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3
votes
3
answers
2k
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Why is it hopeless to view differential geometry as the limit of a discrete geometry?
This is a follow-up question to Introductions to discrete space-time:
Why is this line of thought hopeless?
Classical mechanics can be understood
as the limit of relativistic mechanics
$RM_c$ ...
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1
vote
3
answers
405
views
Can special relativity be deduced from $E=mc^2$?
So instead of assuming that the velocity $c$ is a maximal velocity, proving that while assuming $E=mc^2$.
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