1
vote
1answer
118 views

Is “now” the bounding edge of the universe in the time dimension? [duplicate]

The universe is expanding in the 3 spatial dimensions, could it not also be expanding in time dimension. In other words, are we stuck in 3 dimensions because we are riding the "bow wave" of the big ...
1
vote
0answers
72 views

How should a math undergrad student prepare himself to study GR and QM? [duplicate]

I'm quite sure that similar questions like this have been asked for more than thousands of times on here but since each person's background and interests are unique I believe questions like this ...
0
votes
1answer
108 views

Problem in Grandfather paradox

I am very confused about a paradox and a recent research on Quantum particles. I have read an article which states that time travel is possible for quantum particles. If it is possible then why does ...
6
votes
2answers
233 views

Is there a simple layman way to explain the incompatibilities between quantum mechanics and (general) relativity to high school students?

Is there a simple layman way that I can use to explain the incompatibilities between quantum mechanics and (general) relativity to high school students (people with not much knowledge of the intricate ...
2
votes
1answer
160 views

What happens when an electron jumps through the event horizon of a black hole?

If quantum teleportation is performed into a black hole (by an electron for example), what happens to that electron? Let's say a hydrogen atom is very close to a black hole and the electron jumps ...
4
votes
2answers
193 views

Unitary representations of the diffeomorphism group in curved spacetime

In (special) relativistic quantum mechanics there is a standard argument that says that the (rigged) Hilbert space of states $H$ should be equipped with a projective unitary representation $U$ of the ...
4
votes
1answer
111 views

Definition of vacuum in field theory; Connection between the classical definition and the connection to QFT

I am a bit confused by what is defined to be a vacuum in field theory. Classically a vaccum state is defined to be the state where the field sits at some minima of the potential $\frac{\partial ...
1
vote
2answers
100 views

Hawking evaporation is due to NEGATIVE mass?

So I have seen an animation about Stephen Hawking (after his recent study state universes claim) that Hawking evaporation is due to negative mass; But how is this possible? I mean, there is no such ...
0
votes
0answers
39 views

Quantum Mechanics and General Relativity in Macroscopic Level [duplicate]

Hi I read a book yesterday.The book was Brian Greene's The Elegant Universe. I learned that uncertainty principle affects space-time very microscopic levels and this affection makes conflict in ...
2
votes
1answer
313 views

Can a macroscopic body have wavelength as that of electron? [duplicate]

Einstein has suggested that light can behave as a wave as well as like a particle i.e, it has dual character. In 1924, de-Broglie suggested that just as light exhibits wave and particle properties, ...
0
votes
0answers
47 views

General relativity && quantum mechanics “incompatibillity” [duplicate]

Now this may be utterly weird layman-physics-question, but anyways... I have read recently following: "The fundamental universe laws are everywhere the same. It's just that the manifestation (!) of ...
8
votes
1answer
276 views

Is a QFT in a classical curved spacetime background a self-consistent theory?

EDIT: Better rewording by Chris White: Is it possible to have a theory that treats both GR and QFT (e.g. QFT on a curved spacetime dynamically influenced by the standard QFT fields)? Is such a theory ...
0
votes
0answers
42 views

Resource for nonphysicists about QM/GR incompatibility [duplicate]

I don't know how to explain the issues at hand in a way that nonphysicists are certain to understand. Can anyone point me to some resource (book, video, it doesn't really matter) that will help me?
6
votes
1answer
145 views

Resultant curvature tensor from the Casimir Effect

I've often seen the Casimir effect cited as a source of negative energy/exotic matter with regards to ideas like the Alcubierre drive. The articles then go on to note that the energy required by the ...
1
vote
1answer
449 views

What are the Conflicting Predictions of General Relativity & Quantum Mechanics? [duplicate]

I see a lot of questions in various sites about why the 2 theories are or aren't incompatible, I'm satisfied as to why that's the case. However it has been mentioned that both theories make ...
3
votes
3answers
621 views

Can we apply Schrodinger equation in Newton Gravitational potential and derive the deterministic Newton's gravitation as a special case of it

We know the solutions for wave functions of a an hydrogen atom, and the energy values as given by spectral analysis of radiation emitted by Hydrogen, confirms the possible energy states as predicted ...
1
vote
1answer
88 views

Incompatibility of GR and QM [duplicate]

I am told that the theories of General Relativity and Quantum Mechanics are fundamentally incompatible... Why is that? Someone explained that it had to do with the fact that quantum particles such As ...
1
vote
2answers
120 views

Are there problems solvable with Newtonian physics, GR and QM?

First I must let you know that I don't have much understanding of neither GR nor quantum mechanics, and therefore this question. I've mentally pictured Newtonian physics, GR and quantum mechanics all ...
3
votes
1answer
156 views

Going through a ring of black holes

Mathematician here with a speculative physical question -- feel free to boot me if the level isn't right. Suppose one finds, or builds, a constellation of several black holes arranged in a circle. ...
4
votes
2answers
557 views

The Uncertainty Principle and Black Holes

What are the consequences of applying the uncertainty principle to black holes? Does the uncertainty principle need to be modified in the context of a black hole and if so what are the implications ...
1
vote
1answer
172 views

Relationship between a formal vector derivative and time evolution of an operator

I'm an undergraduate in physics, with all the lack of knowledge inherent in that. In two of my classes, my professors introduced two equations which look eerily similar. The first, from general ...
18
votes
1answer
590 views

Does local physics depend on global topology?

Motivating Example In standard treatments of AdS/CFT (MAGOO for example), one defines $\mathrm{AdS}_{p+2}$ as a particular embedded submanifold of $\mathbb R^{2,p+1}$ which gives it topology ...
8
votes
2answers
188 views

Could an ultra-relativistic particle tunnel directly through a stellar mass black hole?

It occurred to me in passing that the Lorentz contraction of a black hole from the perspective of an ultra-relativistic (Lorentz factor larger than about 10^16) particle could reduce the thickness of ...
2
votes
0answers
104 views

Showing that the Ricci scalar equals a product of commutators

I have to compute the square of the Dirac operator, $D=\gamma^a e^\mu_a D_\mu$ , in curved space time ($D_\mu\Psi=\partial_\mu \Psi + A_\mu ^{ab}\Sigma_{ab}$ is the covariant derivative of the spinor ...
1
vote
0answers
89 views

Does quantum Zeno effect play role in astrophysics?

For example, do two galaxies situated in proximity reduce the atom decay rate in each other? What happens with decay quanta escaped to infinity? Does the radius of apparent horizon effect the ...
8
votes
2answers
400 views

Wavefunction collapse and gravity

If gravity can be thought of as both a wave (the gravitational wave, as predicted to exist by Albert Einstein and certain calculations) and a particle (the graviton), would it make sense to apply ...
0
votes
1answer
180 views

Information faster-than-light and GR vs. QM

What is meant by the statement that information cannot travel faster than light? If I write down something on a paper, isn't there according to QM a non-zero probability that an identical paper can ...
0
votes
0answers
80 views

Counterpart of the Klein Gordon Equation on the “Coordinate Shell”

The relation $$\psi=Ce^{i/\hbar(Et-\mathbf{p}\cdot\mathbf{x})}\tag{1}$$ satisfies the Klein Gordon equation on the mass shell, i.e. for $E^2=p^2+m^2$. Now let's think in the reverse direction. ...
16
votes
3answers
632 views

Is there a thought experiment which brings to light the contradiction between General Relativity and Quantum Mechanics?

I've been told that GR and QM are not compatible, is there an intuitive reason/thought experiment which demonstrates the issue? (Or one of the issues?)
1
vote
2answers
251 views

What's the relationship between quantum entanglement and the relativity of time?

Apologies in advance for what may be a stupid question from a layman. In reading recently about quantum entanglement, I understood there to be a direct link between entangled particles, even at ...
4
votes
1answer
187 views

quantum curvature

If a state can be a superposition of energy states, and mass equals energy (special relativity), and mass curves space-time (general relativity), then could we say that space-time around a quantum ...
1
vote
1answer
1k 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 ...
0
votes
1answer
128 views

Can we develop in the future a technology that can send a message to the past? [duplicate]

Possible Duplicate: Is it possible to go back in time? I believe that everything is possible in this world. If that can be done then why aren't we receiving any message from the future.
6
votes
1answer
516 views

Wick rotation and the arrow of time

It is well known that we can switch from a statistical system to a quantum mechanical system by a Wick rotation. Has this rotation some implication on the way the time flow? namely, this is an ...
5
votes
2answers
1k views

Incompatibility Between Relativity and Quantum Mechanics

Why does Gravity distort space and time while the electromagnetic, strong, and weak forces do not? Does this have to do with why Quantum Mechanics and Relativity are incompatible?
9
votes
5answers
996 views

Why is Mendel Sachs's work not taken seriously? Or is it? [closed]

Back in college I remember coming across a few books in the physics library by Mendel Sachs. Examples are: General Relativity and Matter Quantum Mechanics and Gravity Quantum Mechanics from General ...
2
votes
2answers
185 views

Can the implications of dark energy be used to bridge the gap between Quantum Mechanics and General Relativity?

Can the findings of the Physics Nobel Laureates of 2011, namely the overpowering existence of dark energy (vacuum energy) have any implications in the quest the combine Quantum Mechanics and General ...
7
votes
1answer
244 views

Scale set by cosmological constant

Following on Jim Graber's answer to: Can "big rip" rip apart an atomic nucleus? If the cosmological constant is large enough, even the ground state of a hydrogen atom can be affected. So ...
13
votes
6answers
2k views

Is the Planck length Lorentz invariant?

The planck length is defined as $l_P = \sqrt{\frac{\hbar G}{c^3}}$. So it is a combination of the constants $c, h, G$ which I believe are all Lorentz invariants. So I think the Planck length should ...
13
votes
4answers
3k views

Is there a maximum possible acceleration?

I'm thinking equivalence principle, possibilities of unbounded space-time curvature, quantum gravity ...
12
votes
5answers
2k views

What is the conserved quantity of a scale-invariant universe?

Consider that we have a system described by a wavefunction psi(x). We then make an exact copy of the system, and anything associated with it, (including the inner cogs and gears of the elementary ...
1
vote
2answers
378 views

What is an analog to QM's Hilbert space in GR?

I've read that QM operates in a Hilbert space (where the state functions live). I don't know if its meaningful to ask such a question, what are the answers to an analogous questions on GR and ...
15
votes
3answers
2k views

Nature of gravity: gravitons, curvature of space-time or both?

General relativity tells us that what we perceive as gravity is curvature of space-time. On the other hand (as I understand it) gravity can be understood as a force between objects which are ...
38
votes
5answers
5k views

A list of inconveniences between quantum mechanics and (general) relativity?

It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them? E.g. relativity ...