Tagged Questions

19
votes
3answers
570 views

Why is gravity such a unique force?

My knowledge on this particular field of physics is very sketchy, but I frequently hear of a theoretical "graviton", the quantum of the gravitational field. So I guess most physicists' assumption is ...
4
votes
1answer
175 views

Is the quantization of gravity necessary for a quantum theory of gravity? Part II

(At the suggestion of the user markovchain, I have decided to take a very large edit/addition to the original question, and ask it as a separate question altogether.) Here it is: I have since ...
14
votes
7answers
591 views

Is the quantization of gravity necessary for a quantum theory of gravity?

The other day in my string theory class, I asked the professor why we wanted to quantize gravity, in the sense that we want to treat the metric on space-time as a quantum field, as opposed to, for ...
3
votes
0answers
42 views

Attractiveness of spin 2 gauge theories [duplicate]

Possible Duplicate: Why is gravitation force always attractive? I have heard that the attractiveness of gravitation is due to the fact that it is a spin 2 gauge theory. Why is this so? I ...
3
votes
1answer
134 views

Formation of a black hole and Hawking radiation

From the perspective of an outside observer it takes infinitely long for the black hole to form. But if the black hole is no extremal black hole, it emits Hawking radiation. So the outside observer ...
1
vote
1answer
199 views

Special relativity paradox and gravitation/acceleration equivalence

One of the features of the black hole complementarity is the following : According to an external observer, the infinite time dilation at the horizon itself makes it appear as if it takes an ...
1
vote
0answers
57 views

Thermal gravitational radiation and its detection

To my poor knowledge on the topic, the gravitational waves that are most likely to be detected by LIGO or other experiments do not have thermal spectrum. But I'm not certain. I know that Hawking's ...
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 ...
0
votes
2answers
135 views

How do we end up with a gravity-dominant macroscopic universe from a quantum world having weakest gravity?

At quantum scale, gravity is the weakest force. Its even negligible in front of weak force, electromagnetic force, strong force. At macroscopic scale, we see gravity everywhere. Its actually ruling ...
-4
votes
1answer
153 views

Why did Standard Model never sense a requirement to include gravitational quantum?

Standard Model is advanced version of Quantum physics. It tried to include everything which came in the way while understanding quantum world. It even didn't bother to include even Higgs Boson which ...
2
votes
3answers
341 views

What happens to matter in extremely high gravity?

Though I am a software engineer, I have bit interest in sciences as well. I was reading about black holes and I thought if there is any existing research results on How matter gets affected because of ...
3
votes
1answer
153 views

Gravity and Planck scale

What is the connection between Planck's constant and gravity? Why is the Planck scale the natural scale for quantum gravity? I would have though the scale would be related to G, not h.
3
votes
2answers
464 views

Why does the force of gravity get weaker as it travels through the dimensions?

Some theories predict that the graviton exists in a dimension that we of course can't see, and that is why the force of gravity is so weak. Because by the time gravity has got from the dimension in ...
3
votes
3answers
514 views

How does gravity force get transmitted?

How does gravity force get transmitted? It is not transmitted by particles I guess. Because if it was, then its propagation speed would be limited by the speed of light. If it is not transmitted by ...
1
vote
4answers
373 views

Why is gravity weak at the quantum level?

Why is gravity stronger than other forces at the macroscopic level, yet weaker than other forces at the quantum level? Is there an explanation?
2
votes
1answer
256 views

Why are there Gravitons among the modes of oscillation in String Theory?

Why are gravitons present among the modes of oscillation of the 'strings' in String Theory?
2
votes
0answers
101 views

What results from particle collision would ensure the existence of the graviton?

I understand that particles are smashed together to try to enable us to detect some sort of graviton presence but we can't actually detect a graviton due to the fact that it 'exists' in some extra ...
6
votes
1answer
81 views

Quantum mechanical gravitational bound states

The quantum mechanics of Coloumb-force bound states of atomic nuclei and electrons lead to the extremely rich theory of molecules. In particular, I think the richness of the theory is related to the ...
14
votes
1answer
62 views

Instantons and Non Perturbative Amplitudes in Gravity

In perturbative QFT in flat spacetime the perturbation expansion typically does not converge, and estimates of the large order behaviour of perturbative amplitudes reveals ambiguity of the ...
5
votes
2answers
220 views

Possibility of “graviballs”?

Looking at the relevant wikipedia page, one can read that the graviton should be massless. Is it 100 % certain that it is massless or is there room in any "nonstandard" models for a tiny non-zero mass ...
0
votes
1answer
153 views

Sun-Earth Virtual Gravitons?

How many virtual gravitons do the sun and earth exchange in one year? What are their wavelengths?
2
votes
2answers
436 views

Three-Dimensional Gravity

Does anyone have any references that discuss gravity in three-dimensions? I'm trying to make my way through some papers by Witten relating $SL(2,\mathbb{C})$ Chern-Simons theory and gravity in three ...
1
vote
0answers
256 views

Quantization of Gravitational Field: Quantization conditions

I'm begining to study Quantization of field with the second quantization formalism. I've studied phononic field, electromagnetic field in the vacuum and a generic relativistical scalar field. I ...
4
votes
1answer
325 views

Quantum Gravity and Calculations of Mercury's Perihelion

In an astronomy forum that I frequent, I have been having a discussion where the state of quantum gravity research came up. I claimed that Loop Quantum Gravity theories couldn't prove GR in the ...