Reputation
3,729
Top tag
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
4 15 38
Impact
~139k people reached

Jan
1
comment Why is the formulation of M(embrane) theory so hard?
The difficulty isn't in formulating the membranes, which exist even in the 10-dimensional string theories (in certain formalisms, anyway). The difficulty in formulating M-theory is that in its definition it's a theory which gives the Heterotic E and Type IIA string theories respectively when compactified on a line segment and circle respectively. 10-dimensional string theories were derived because we could, and some turned out to be remarkably consistent with the Standard Model, while M-theory is to be written based on certain defined properties.
Nov
25
awarded  Popular Question
Nov
18
revised Why does string theory require 9 dimensions of space and one dimension of time?
added 29 characters in body
Nov
7
comment Boundary stress-energy tensor form ADS/CFT
There is an answer at PhysicsOverflow.
Oct
13
revised How to learn physics?
deleted 575 characters in body
Oct
13
revised How to learn physics?
deleted 575 characters in body
Oct
9
comment Why does light always travel in a straight line?
@MBN Of course. I was only responding to the questioner, who probably wasn't referring to geodesics. Or so I guess.
Sep
9
comment Stone dropped from a moving train
For both questions, because the stone isn't accelerating - it's moving horizontally at the same speed as that of the train when the stone was dropped, but acceleration would require a constant force being applied on it.
Aug
18
revised What S means in S-duality?
S-duality is not exclusive to string theory.
Aug
18
comment What S means in S-duality?
S-duality is a duality between strong coupling and weak coupling, so I'd guess it comes from the "strong", as in "strong-weak".
Aug
9
comment In string-net condensation, what does the quantized charge means?
I don't think there is anything unclear about this question. Regarding the first question - As explained here by Xiao-Gang Wen, it has to do with the boundary of the string being discrete.
Jul
24
revised Why there is no Gibb's phenomenon in QM?
deleted 202 characters in body
Jun
30
comment Why are there no branes in heterotic string theory?
Actually, there are branes in heterotic string theory, but they just don't behave as boundary conditions for fundamental strings. See here for an answer.
Jun
29
awarded  Pundit
Jun
20
comment Quantum mechanic particle
@Qmechanic Are you sure you meant to add the "supersymmetry" (or for that matter, "operators") tag here?
Jun
20
comment What equation do we use to measure the energy level of a string, to determine it's “particle correlation”
@CuriousOne That's not true - the MSSM is found in many string vacua. The "lack of progress with it in particle physics" is a different, and historical issue. String theory currently is formulated very differently from its origins in QCD.
Jun
20
comment What equation do we use to measure the energy level of a string, to determine it's “particle correlation”
(contd.) and then use the mass ratios from the mass spectrum to compute the mass of other particles.
Jun
20
comment What equation do we use to measure the energy level of a string, to determine it's “particle correlation”
The mass spectrum string theory is just $m=\sqrt{N-a}$ (in appropriate natural units), where $N$ is the so-called "number operator" that takes non-negative integer and half-integer values. $a$ is 1 in the bosonic string theory, and 0 or 1/2, depending on the sector, for superstrings. Of course, the natural units involve setting the string length to 1, so the mass spectrum actually only allows the calculation of mass ratios, obtaining the mass in S.I. units would need experimental measurement (existing experimental measurement is enough. You can just use, e.g. the mass of the electron, (contd.)
Jun
19
comment Particle position and speed
Woah, this is one confused question. The wave in question is a probability amplitude. It has nothing to do with the momentum of the particle being zero or non-zero.
Apr
25
comment In an elastic collision, can we choose between cons. of energy and cons. of momentum?
Both are conserved in elastic collisions. Not sure what you mean by "choose" - you simply use whatever's important to find out whatever you want to find out. A general elastic collision with known masses and initial velocities is usually solved with both.