116,084 reputation
7180347
bio website motls.blogspot.com
location Czech Republic
age 41
visits member for 4 years, 7 months
seen 3 hours ago

Hi, I am a string theorist and a publicist.


Aug
21
comment Could we be on the inside of a concave hollow universe?
Thanks, user, there is obviously a pragmatic perspective from which it's bunk and I would support such a perspective in most practical contexts - when someone would try to use the hollow Earth perspective to advocate... pretty much anything. ;-) But if one really asks only whether it's compatible with the empirical evidence in physics etc., well, it is.
Aug
21
comment Diameter of manifold with negative curvature
Apologies, it seems too mathematically hard for me. Under the normal metric, the unitary group SU manifold is positively curved, isn't it?
Aug
21
comment Why does a moving fan seem transparent?
Dear @DigitalTrauma - I am sorry for that but it's not my fault. Someone simply vetoed your edit probably because it's problematic to change the content of other users' answers if there seems to be nothing "obviously" in need of a change. I would have okayed your edit, of course! ;-) But if you do another edit, I can't guarantee that no one else will look at it before me so my opinion is irrelevant. The editing is a collective activity of the users with a certain reputation or more who get there at the right time.
Aug
21
comment Diameter of manifold with negative curvature
I think it would be more sensible on the math forums. Typically, negative curvature does imply "noncompact" shape i.e. infinite diameter - the hyperbolic space is noncompact, after all. However, you may have things like orbifolds of the hyperbolic planes/spaces which probably may have a finite diameter, unless I misunderstand something.
Aug
21
revised Could we be on the inside of a concave hollow universe?
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Aug
21
revised Could we be on the inside of a concave hollow universe?
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Aug
21
answered Could we be on the inside of a concave hollow universe?
Aug
21
answered If we attach a fan at the end of a boat and switch it on, will the boat move?
Aug
21
revised $U(1)$ local gauge invariance in QED
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Aug
21
answered $U(1)$ local gauge invariance in QED
Aug
21
revised Why does a moving fan seem transparent?
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Aug
21
comment Global symmetries in type IIB string theory vs type IIB supergravity
Good question. I think that the limit is a bit harder to see on the gauge theory side. Try to see e.g. arxiv.org/abs/hep-th/9811047
Aug
21
revised Global symmetries in type IIB string theory vs type IIB supergravity
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Aug
21
answered Power of a wave in a string
Aug
21
awarded  Good Answer
Aug
21
revised Global symmetries in type IIB string theory vs type IIB supergravity
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Aug
21
answered Global symmetries in type IIB string theory vs type IIB supergravity
Aug
21
revised Euclidean geometry in non-inertial frame
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Aug
21
revised Euclidean geometry in non-inertial frame
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Aug
21
reviewed Approve Am I attracting Pluto?