112,165 reputation
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bio website motls.blogspot.com
location Czech Republic
age 41
visits member for 4 years, 4 months
seen 8 hours ago

Hi, I am a string theorist and a publicist.


Jun
9
answered Why do we say that the earth moves around the sun?
Jun
8
answered Why photons transfer to electrons perpendicular momentum?
Jun
8
reviewed Approve Formulas for ball rolling in a bowl?
Jun
8
comment Do apparent event horizons have Hawking radiation?
Hi, thanks for your interest! Well, yes, almost: the acceleration $1g$ is $10m/s^2$ so $c^2/g$ is $10^{17}/10=10^{16}$ meters. That's actually one third of a parsec, so if you were guessing, it was nearly perfect. The wavelength of the thermal radiation is a parsec, too - so clearly, these are no photons that can be meaningfully measured. For small accelerations like this one, it is a purely academic exercise.
Jun
8
comment Why should the observed probability distributions in quantum mechanics always align with the pointer basis of decoherence?
If I understand you correctly, then yes! ;-) Decoherence is just a particular process, and/or a calculation imitating this process, that just allows one to trace what the eigenstates of the density matrix will be. But the fact that the basis in which $\rho$ is diagonal is preferred for defining "alternative histories or outcomes" whose probabilities may be nicely checked and "perceived" is an independent fact.
Jun
7
revised Do apparent event horizons have Hawking radiation?
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Jun
7
comment Do apparent event horizons have Hawking radiation?
Dear @Cell-o, yes, one will get "contradictions" between different observers because different observers will indeed see different things, depending on their acceleration or the lack of. And indeed, Zassounotsukushi's event horizon depends on the observer but it's still real and for many purposes, as the OP correctly expected, it has the same properties as the "objective" event horizon of a black hole. That's guaranteed by the principle of relativity and equivalence, too. In physics, Zass.' horizon is known as Rindler horizon en.wikipedia.org/wiki/Rindler_coordinates#The_Rindler_horizon
Jun
7
revised Do apparent event horizons have Hawking radiation?
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Jun
7
answered Do apparent event horizons have Hawking radiation?
Jun
7
answered Why isn't black hole information loss this easy (am I missing something basic)?
Jun
6
answered Why should the observed probability distributions in quantum mechanics always align with the pointer basis of decoherence?
Jun
6
answered If 100% of the energy from the sun is reflected back into space
Jun
5
comment Do Neveu-Schwarz conditions make sense?
The boundary terms in $\delta S$, coming from integration by parts, are $\psi_\mu \delta \psi^\mu |^{\pi}_0-\tilde\psi_\mu \delta \tilde\psi^\mu |^{\pi}_0$ . This can vanish either by making $\psi$ and $\tilde\psi$ periodic or by setting $\psi=\pm\tilde\psi$ at both boundary points $\sigma=0,\pi$. The relative sign in these $\pm$ among both endpoints indeed gives an open string version of (anti)periodicity that leads to integral or half-integral modes. But it is (anti)periodicity over a doubled range only.
Jun
5
comment Do Neveu-Schwarz conditions make sense?
Dear @James, if fields are periodic, $X_{or \,\,\psi}(\sigma+\pi)=X_{or\,\,\psi}(\sigma)$, then the topology is a circle because $\sigma$ is effectively a periodic variable, and it's called the closed string. For both open strings and closed strings, the condition constraining boundary condition is the vanishing of the boundary terms in $\delta S$.
Jun
4
reviewed Approve Questions about the Dyson equation
Jun
3
reviewed Approve Do Neveu-Schwarz conditions make sense?
Jun
3
revised Do Neveu-Schwarz conditions make sense?
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Jun
3
answered Do Neveu-Schwarz conditions make sense?
Jun
2
comment Is there any proof for the 2nd law of thermodynamics?
Dear Bjorn, it's an OK can of worms. In the particular proof Boltzmann chose, he assumed molecular chaos, a particular assumption about the lack of correlations in the initial state. There can be correlations but it's still true that it's exponentially unlikely that they will modify the qualitative answer - they would just make the quantitative calculation more ambiguous. Moreover, there may also be an assumption that particles are dumb but this assumption can be proved, cannot it? ;-) Things that are clever, like eggs and fridges, may lower their entropy but they increase $S_{environment}$.
Jun
2
comment Does kaon decay etc prove “CP violation” or just “CP or CPT violation”
Plus one, Anna! ;-)