Tagged Questions
0
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0answers
77 views
How can it be seen that ST unifies GR and QM as the quantum gravity scale is not directly accessible
I am a newbie to superstring theories, but I came into this question:
so superstring theories purport to unify general relativity and quantum theory.
However, there is yet no definitive way to test ...
2
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1answer
88 views
Energy Functional
I am a graduate student in pure mathematics, during my study on Ricci Flow I faced some functional known as energy functional. For example Einstein-Hilbert functional is called an energy functional, ...
-5
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0answers
60 views
Consequences of Third Postulate of Special Relativity [closed]
Consequences of SR arise from two postulates.
know as this abstract states:
"relativistic action is limited to planck's constant", and maybe we've to consider it as the possible third postulate of ...
1
vote
1answer
69 views
Can the fuzzball conjecture be applied to microscopically explain the entropy of a region beyond the gravitational observer horizon?
In this article discussing this and related papers, it is explained among other things, how the neighborhood of an observer's worldline can be approximated by a region of Minkowsky spacetime.
If I ...
2
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1answer
90 views
Strings on a curved spacetime
Suppose we are interested in in string on a specific metric G, is it necessary to include a Dilaton field on back ground in order to preserve the Weyl invariance? suppose the spacetime is not empty, ...
5
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1answer
252 views
In what limit does string theory reproduce general relativity?
In quantum mechanical systems which have classical counterparts, we can typically recover classical mechanics by letting $\hbar \rightarrow 0$. Is recovering Einstein's field equations (conceptually) ...
5
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2answers
398 views
What is background independence and how important is it?
What is background independence and how important is it?
In order to be a theory of everything, will the final string-theory/m-theory have to be background independent?
Does the current lack of ...
3
votes
0answers
256 views
How do the Einstein's equations come out of string theory?
The classical theory of spacetime geometry that we call gravity consists of the Einstein equation, which relates the curvature of spacetime to the distribution of matter and energy in spacetime.
for ...
8
votes
1answer
496 views
Is String Theory formulated in flat or curved spacetime?
String Theory is formulated in 10 or 11 (or 26?) dimensions where it is assumed that all of the space dimensions except for 3 (large) space dimensions and 1 time dimension are a compact manifold with ...
1
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0answers
101 views
Extending General Relativity with Kahler Manifolds?
Standard general relativity is based on Riemannian manifolds.
However, the simplest extension of Riemannian manifolds seems to be Kahler manifolds, which have a complex (hermitian) structure, a ...
4
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0answers
130 views
Implications of Unruh-inertia to theories of gravity
If it turns out to be true that the galaxy rotation curves can be explained away by Unruh modes that become greater than the Hubble scale at accelerations around $10^{-10} m/s^2$ as proposed in here, ...
3
votes
1answer
120 views
Where does this equation for a perturbed metric come from?
I'm reading an article which includes the following equation involving a perturbed metric:
$$G_{AB} = \eta_{AB} + \overset{1}{\gamma}_{AB} + 2\overset{1}{\chi}_{(A,B)}\tag{4.1}$$
I don't understand ...
-1
votes
1answer
148 views
What if microstates increase proportional to universe volume?
I am probably a delusional crank with a lot of crazy, overly speculative conjectures. If I am not delusional, than at the very least I've been ahead of the curve, the last 40 or so years. I was a ...
0
votes
3answers
246 views
Laws of gravity for a universe that only consists of two objects?
So, we know that when two objects of normal matter get away from each other, the gravitational pull they feel from each other, decreases.
I wanted to see how that would work. And in my ...
1
vote
1answer
878 views
What's next after Higgs Boson discovery? [duplicate]
Possible Duplicate:
Practical matter of the Higgs-Mechanism
As everybody knows that the Higgs Boson was discovered on July 4th,2012, I am so curious about it.
What are the possible ...
2
votes
1answer
286 views
General Relativity - Einstein field equation and quantum field theory
Einstein field equation has many solutions. Out of them, is there any solution that is incompatible with quantum field theory?
Also, what solutions of Einstein field equation would be incompatible ...
8
votes
5answers
573 views
How does the string worldsheet affect the space-time in which they live?
I don't understand much about string theory and never really got much further past the Nambu-Goto action and very basic supersymmetry (SUSY) lectures in my undergraduate courses, but the only thing ...
10
votes
0answers
275 views
A dictionary of string - standard physics correspondences
Motivated by the (for me very useful) remark
''Standard model generations in string theory are the Euler number of
the Calabi Yau, and it is actually reasonably doable to get 4,6,8, or 3
...
3
votes
1answer
170 views
Could strings be geons?
Is it possible that string theory strings are geons? This may be an overly speculative or naive question, but is there an obvious reason why not? Both strings and geons seem to have roughly the same ...
4
votes
2answers
452 views
Critics of Mannheim's Conformal Gravity Theory?
I'm looking for more articles/reactions/critiques/support for Philip Mannheim's recent conformal gravity theory.
See here: http://arxiv.org/abs/1101.2186v1
Any ideas on where to start?
4
votes
0answers
25 views
What is the state-of-the-art on spacelike singularities in string theory?
What lessons do we have from string theory regarding the fate of singularities in general relativity?
What happens to black hole singularities? What happens to cosmological singularities?
Which ...
4
votes
1answer
706 views
What do “tachionic” neutrinos mean for QG?
Reading about the spectacular Opera claim, I`m (again ;-P) wondering if a confirmation of superliminous neutrinos could help settle some still open quantum gravity issues ...?
In this post, Lumo ...
3
votes
2answers
296 views
Singularities and quantized space time
Discrete space time quanta would solve the problems of infinite densities for singularities in General Relativity and Quantum Gravity by imposing a non zero limit on the minimum radius of black holes. ...
3
votes
2answers
245 views
How is the complexification of spacetime justified?
As always the caveat is that I am a mathematician with very little knowledge of physics. I've started my quest for knowledge in this field, but am very very far from having a good grasp.
General ...
9
votes
3answers
584 views
Does gravity require strings?
OK, before I ask my question, let me frame it with a few (uncontroversial?) statements:
The low-field-limit plane-wave solution to Einstein's equations is helicity-2.
In the early days of string ...
0
votes
1answer
146 views
Meaning and types of singularity in case of string or any cosmological model (Mathematical description)
What is actual meaning of singularity can we use this term for conclusion in any research paper( related to cosmological models ).what r the types .
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2answers
538 views
Black Hole Singularity and String Theory
This question arises in a somewhat naive form because I am largely unfamiliar with String Theory. I do know that it incorporates higher space dimensions where I shall take the overall dimensionality ...
-3
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1answer
200 views
Why String theory introduced in cosmological models to study nature of universe? [closed]
Why String theory ? simple cosmological model is not sufficient for study of nature of universe
2
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0answers
210 views
Singularities in Bianchi models in general relativity ( physical science)
what are the conditions to check point type singularity in a bianchi type model ?
bianchi type model are of Type I,II,III,IX,IV or u can say we use different Bianchi type models having some specific ...
7
votes
2answers
632 views
Do traversable wormholes exist as solutions to string theory?
There has been some heated debate as to whether the laws of physics allow for traversable wormholes. Some physicists claim we require exotic matter to construct wormholes, but then others counter the ...
3
votes
3answers
522 views
How could spacetime become discretised at the Planck scale?
I didn't have much luck getting a response to this question before so I have tried to reword and expand it a little:
In early 2010 I attended this inaugural lecture by string theorist- Prof. ...
4
votes
2answers
228 views
How to check Einstein-like equations on their correspondence with the real world?
Physicists studying the grounds of physics and some mathematicians often come to a theories which are like a general-relativity, but do not coincide with it. Often these theories contradict the real ...
