Dear @anna, yes, the electron is pretty likely to be the last “remainder” of a black hole. Before it becomes an electron, the black hole may be a W boson that decays into an electron and a neutrino. Before it was a W boson, it could have been a much more excited string state… – Lubos Motl Feb 28 ’11 at 8:18
     
… the conclusion that black hole microstates are continuously connected to (other) elementary particle species – there’s no qualitative difference – doesn’t really depend on specific features of string theory. It’s a general fact that strings just confirm and make more specific.

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— Mar 1 ’11 at 15:20

— Lubos Motl

2014.07.21 Monday ACHK

Are elementary particles ultimate fate of black holes?

From the “no hair theorem” we know that black holes have only 3 characteristic external observables, mass, electric charge and angular momentum (except the possible exceptions in the higher dimensional theories). These make them very similar to elementary particles. One question naively comes to mind. Is it possible that elementary particles are ultimate nuggets of the final stages of black holes after emitting all the Hawking radiation it could?

Yes, black holes are special kinds of elementary particles. That’s how they have to be represented in every consistent quantum theory of gravity. This representation of a black hole becomes especially useful and important for small black holes – whose mass is not much larger than the Planck mass.

And indeed, a black hole evaporates, which is just a form of a decay of a heavy elementary particle, and when it becomes very light, at the end of the Hawking evaporation process, it is literally indistinguishable from a heavy elementary particle that ultimately decays into a few stable elementary particles.

However, a difference that you seem to neglect is that black holes actually carry a large entropy

S = \frac{A}{4A_0} k_B

where A is the area of the black hole’s event horizon and ( A_0 ) is the Planck area ( A_0=\hbar G / c^3 ). The constant ( k_B ) is Boltzmann’s constant. This means that there actually exists a huge number of microstates

N = \exp(S / k_B)

and a single black hole, with a fixed value of mass, charges, and spin, is just a macroscopic description of the ensemble of N “microstates”. In reality, the black hole carries a huge information – the world distinguishes which of the N microstates is actually present.

It is these “microstates” that are really analogous to types of elementary particles. But the number of particle species that macroscopically look like the black hole of given mass, charges, and spin is not one: instead, it is huge, approximately N.

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— answered Feb 27 ’11 at 16:45

— Lubos Motl

2014.07.18 Friday ACHK

Als 4 days ago

I’m happy to see that you still work on string theory. Do you intend to start publishing again?

Lubos Motl Als 3 days ago

No, I do not.

Kimmo Rouvari Lubos Motl 3 days ago

Why? (just curious) Obviously you have ideas and something to say.

Lubos Motl Kimmo Rouvari 3 days ago

I just virtually never had a real pleasure out of this process which has something like dozens of consumers in the world in average and which is laborious and demanding various formalities. This part of what I would be doing was always more or less just work and I was doing these things as a part of the package for the salary.

I am not getting the income for that, I am not a communist who would think it’s really right to do the expert work for free, so I won’t do these things. I think it’s common sense and it’s very simple.

I am sufficiently frustrated when I just report on someone’s excellent paper and the feedback is 100 times less excited than the feedback following some anti-science rant by a worthless sithead … And that’s something I may ignore because it’s just not my business.

— Lubos Motl

2014.07.15 Tuesday ACHK

However, general relativity predicts and experiments confirm that gravitational waves do exist: the relevant observations were awarded by the 1993 physics Nobel prize, too. The waves are vibrations of the space itself. It means that the metric tensor remembers the information about the geometry – and curvature at each point, even in the empty space, something that Mach’s principle specifically wanted to prohibit.

…

Einstein had thought that Mach’s Principle was the way to go because it (also) made the universality encoded in the equivalence principle manifest. The equivalence principle says that all objects will be influenced equally – the same acceleration – by the whatever agent is causing gravity. Mach’s principle satisfies the criterion “totally” – it removes any field-like agent. Well, it’s going “too far” in this sense. Of course that Einstein was struggling for years to make Mach’s Principle compatible with the speed limit c – and GR is what eventually came out of it.

– Lubos Motl

2014.06.29 Sunday ACHK

In theoretical physics, particularly in discussions of gravitation theories, a Mach principle is any of a class of principles which are more specific statements of Mach’s principle.

The broad notion is that “mass there influences inertia here”. Any statement which — though possibly far more specific than this — follows in this spirit may be classified as a “Mach principle”. The truth of these statements depends on the particular statement. (The truth also depends on the theory of gravity, though Einstein’s general relativity is the most frequently discussed theory.)

Examples

Hermann Bondi and Joseph Samuel have listed eleven distinct statements which can be called Mach principles, labelled by Mach0 through Mach10. Though their list is not necessarily exhaustive, it does give a flavor for the variety possible.

• Mach0: The universe, as represented by the average motion of distant galaxies, does not appear to rotate relative to local inertial frames.
• Mach1: Newton’s gravitational constant G is a dynamical field.
• Mach2: An isolated body in otherwise empty space has no inertia.
• Mach3: Local inertial frames are affected by the cosmic motion and distribution of matter.
• Mach4: The universe is spatially closed.
• Mach5: The total energy, angular and linear momentum of the universe are zero.
• Mach6: Inertial mass is affected by the global distribution of matter.
• Mach7: If you take away all matter, there is no more space.
• Mach8: ( \Omega \ \stackrel{\mathrm{def}}{=}\ 4 \pi \rho G T^2 ) is a definite number, of order unity, where ( \rho ) is the mean density of matter in the universe, and T is the Hubble time.
• Mach9: The theory contains no absolute elements.
• Mach10: Overall rigid rotations and translations of a system are unobservable.

— Wikipedia on Mach principle

2014.06.22 Sunday ACHK

Charge (physics), the susceptibility of a body to one of the fundamental forces

• Color charge, a property of quarks and gluons, related to their strong interactions
• Electric charge, a property which determines the electromagnetic interaction of subatomic particles
• Magnetic charge, a property of theoretical magnetic monopoles

— Wikipedia on Charge

Symmetry and conservation

Conservation of momentum is a mathematical consequence of the homogeneity (shift symmetry) of space (position in space is the canonical conjugate quantity to momentum). That is, conservation of momentum is a consequence of the fact that the laws of physics do not depend on position; this is a special case of Noether’s theorem.

— Wikipedia on Momentum

Momentum is the Noether charge of translational invariance. As such, even fields as well as other things can have momentum, not just particles. However, in curved spacetime which isn’t asymptotically Minkowski, momentum isn’t defined at all.

—

2014.06.19 Thursday ACHK

Maldacena and Susskind proposed to identify ER (non-traversable wormholes i.e. Einstein-Rosen bridges) with EPR (entanglement). The former is a universal geometric visualization of the latter – which may become “simple” in special cases, just like in the case of a duality.

— An anti-ER-EPR paper

— Lubos Motl

2014.05.03 Saturday ACHK