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Questions related from Biswajoy Brahmachari
elements are written in terms of generators S and T 1 , S, T, ST, TS, T2, STS, ,TST, T2ST, TST2, T2S, ST2 How do I multiply S with T2ST from left How do I multiply S with TST2 from left
10 October 2017 5,009 19 View
We know in quantum mechanics position and momentum of a particle do not commute. But in a quantum field theory they must commute if position operator and momentum operator are separated by a space...
07 July 2015 907 46 View
Quantum field theories use Minkowski space whereas statictical mechanics uses 3-D Euclidean space with temperature as an additional variable. Both the theories deal with many particle systems and...
07 July 2015 3,784 2 View
Action at a distance is the simplest non-local interaction. But then in relativistic local field theories signals cannot travel at velocities more than the speed of light. This is taken into...
06 June 2015 4,497 15 View
CPT is a symmetry of fundamental interactions. Therefore CPT conservation is built into relativistic quantum field theories, such as electroweak theory. However we know that CP is violated in weak...
05 May 2015 7,457 15 View
We do not know whether the neutrino is a Dirac particle or a Majorana particle. If neutrino turns out to be a Majorana particle then two additional phases are to be introduced in the 3x3 lepton...
05 May 2015 2,614 18 View
Domain walls or boundaries are expected to form when a discrete symmetry is broken spontaneously. REF: Y. B. Zeldovich, I. Y. Kobzarev and L. B. Okun, Zh. Eksp. Teor. Fiz. 67 (1974) 3 [Sov. Phys....
02 February 2015 7,683 2 View
What is the definition of luminosity distance? What is the motivation behind defining this term? How it is affected by (i) Space time curvature (ii) Redshift (iii) Time dilation
07 July 2014 6,028 0 View
There are a few basic parameters by which the cosmologists try to describe our universe. In classical cosmology the important ones are (i) Hubble parameter (ii) Density parameter (iii)...
06 June 2014 5,332 3 View
In Newtonian notion force between to masses m1 and m2 separated by a distance d is simply G m1 m2/d^2. This is an example of a theory which accepts action at a distance. A second example is...
06 June 2014 1,422 41 View
Group theory finds wide applications in Physics. A branch of Mathematics becomes useful in the description of physical phenomenon, both classical and quantum, happening around us. What are...
06 June 2014 4,095 45 View
Nature of dark energy is unknown. It is a form of energy causing expansion of universe. Satellite based experiments such as Planck has estimated that 68.3 % of total matter and energy is in the...
06 June 2014 4,200 28 View
Recent observation of B mode polarizations encoded in CMB anisotropy has indicated the presence of primordial gravity waves. Do inflationary theories have a mechanism to produce primordial gravity...
05 May 2014 6,054 38 View
In the Newtonian approach gravitational force can be written as the gradient of a scalar field. It is sufficient to know the gravitational scalar potential at each point. Then gravitational field...
05 May 2014 5,043 50 View
The question has following implications 1) What does the term anisotropy mean ? 2) Because universe is homogeneous and isotropic in general how does one expect anisotropies ? 3) Is it a...
05 May 2014 7,199 4 View
When delta T/T is plotted against angular separations between points we see several peaks in the plot. The first one is most prominent one is between l value 200-300, or in terms of angular scales...
05 May 2014 2,145 17 View
A 7 keV sterile neutrino is a good candidate for warm dark matter. What are the feynman diagrams by which a 7 keV sterile neutrino can be produced? What are the decay channels? By which diagram...
04 April 2014 7,541 4 View
Vacuum expectation value (VEV) of the Higgs scalar is responsible for fermion masses and also masses of the W+ W- and Z gauge bosons. Does it mean that the Higgs particle can extract energy out...
03 March 2014 7,432 11 View
LSND experiments observed oscillation between ordinary and sterile neutrinos. Does the Mini-Boone result confirm LSND data ?
02 February 2014 7,489 4 View
Proton lifetime is believed to be comparable to the lifetime of the universe. What is the most recent experimental numbers of proton lifetime ? What are the unified models which are ruled out by...
02 February 2014 1,535 3 View
Inflation is a very attractive theory by which one can explain horizon problem and flatness problem. A successful theory should have experimental tests. My question is that what is the way to get...
02 February 2014 2,406 23 View
If density perturbations are scale invariant then the dependence should be more like k^0, where k is the wave number. Then why do we define that scale invariant perturbations has spectral index 1....
02 February 2014 8,294 2 View
Dark matter density should vary with radial distance to explain flat rotation curves seen in typical spiral galaxies like the milky way. What are the popular density profiles. How do they fit with...
01 January 2014 9,746 25 View
Unless there is a symmetry reason to protect the Higgs mass near the electroweak scale, one loop effects will give large corrections. Is it super-symmetry or is it something else ? Or is it some...
01 January 2014 1,739 2 View
There are several small satellite galaxies of milky way. Namely, Draco, Sextans, Carina, Fornax and others. What do we know about how dark matter is distributed in these satellites? Do we know...
01 January 2014 3,561 11 View
Experimental search for dark matter must rely on some model which tells us how our instruments, which are made of ordinary matter, interact with dark matter. Otherwise we cannot invent the right...
01 January 2014 6,335 11 View
Curvature of space can be estimated from Planck satellite data 2013.
12 December 2013 1,880 9 View
Proposed in late 1997, this correspondence is a theoretical result which implies that M-theory is in some cases is equivalent to a quantum field theory How does one show the equivalence? What is...
01 January 1970 7,736 6 View
