Join together theoretical and particle physicists in the world to share knowledge and ideas.

• Dipankar Das

  Could you suggest some references on SU(2)_L X SU(2)_R X U(1)_B-L theory at an introductory level? I have looked at pati-salam and pati-mahapatra papers.

  I want something where the symmetry breaking part is worked out in detail.

  Recent replies ⋅ Show All (1)

  • 
    Robert Szafron replied

    Check this one http://arxiv.org/abs/hep-ph/9910279

    Apr 19, 2012
• Dipankar Das

  What does it actually mean when one says that the differential scattering cross section blows up in the forward direction?

  Suppose we place a detector in the forward direction (practically not possible) to collect the scattered particles only. Will it collect infinite number of particles for a finite incident flux; or ISuppose we place a detector in the forward direction (practically not possible) to collect the scattered particles only. Will it collect infinite number of particles for a finite incident flux; or I am missing some mathematical subtlety? The question I've posed above is based on the definition of scattering cross section. I am confused, can anyone help?
• Dipankar Das

  What is the value of integration[-1 to +1] x^n/(1-x)*{P_0(x)-P_m(x)} dx at the limit 'm' tending to infinity?

  The value of the definite integral is finite, but does the limit converge to a specific value? The numerator has a zero at x=1 which takes care of the (1-x) at the denominator.

  Recent replies ⋅ Show All (15)

  • 
    Dipankar Das replied

    @Giovanni : Got the picture. Thanks..

    Apr 4, 2012
• Prakash Kumar

  Can muons replace electrons in atoms?

  Muons are also negatively charged particles having 206 times the mass of an electron. It is surprising that muons do not replace electrons in atoms. The cause of this is not yet clear.

  Recent replies ⋅ Show All (5)

  • 
    Prakash Kumar replied

    Dear Mtafu Norwin-Maseleka, The information provided by you is useful to me and satisfies my thirst for knowledge. Thanks again.

    Mar 28, 2012
• C.AmarEshwar Prasad

  Can neutrons ever be accelerated by any means of energy ?

  Can neutrons ever be accelerated by any means of energy ?

  Recent replies ⋅ Show All (8)
• Andrew James Bruce

  Is there any reason why massless electrically charged particles are not allowed?

  It seems an experimental fact that there are no massless electrically charged fundamental fermions. Is there any known reason why this is so? I mean, is there anything in quantum field theory thatIt seems an experimental fact that there are no massless electrically charged fundamental fermions. Is there any known reason why this is so? I mean, is there anything in quantum field theory that makes such things inconsistent? I am certainly not aware of anything that outlaws such particles. Any thoughts welcomed.

  Recent replies ⋅ Show All (56)

  • 
    Sanjay Sood replied

    Another interesting question would be the chirality of a charged spin half massless particle. Would it have both left and right chiralities?

    Mar 22, 2012
• sara Shams

  Why pi meson do not decay into electron?

  Pi meson decay into moun but do not dacay into electron.why?

  Recent replies ⋅ Show All (2)

  • 
    sara Shams replied

    Thanks a lot

    Mar 12, 2012
• Ahmad Ryan

  Monopoles

  Is there any experimental proof to support the existence of the magnetic monopoles?

  Recent replies ⋅ Show All (21)

  • 
    Mtafu Norwin-Maseleka replied

    Very good Sanjay, you have just cleared a terminology based confusion. A 'monopole' is a 'particle' and is not related to the North and South poles created by a spinning charge. Just like 'color'Very good Sanjay, you have just cleared a terminology based confusion. A 'monopole' is a 'particle' and is not related to the North and South poles created by a spinning charge. Just like 'color' is a 'charge' and is not related to the colors of the rainbow. Now, why call it a monopole? Is there a 'dipole'? a 'tripole'? etc.?

    Mar 9, 2012
• Meseret Tiruye

  Do we have something which is "nothing"?

  How do we explain "nothing", which is empty and not vacuum?

  Recent replies ⋅ Show All (21)

  • 
    jean Cimanga Kajingulu replied

    @Brandon Johnson :thanks very much.your help is so great!

    Mar 3, 2012
• Obaid Ullah

  The problem is that neutrino has speed greater than the sped of light ? Is this state fits with the Energy-Momentum relationship and Dirac Equation?

  Neutrino puzzle

  Recent replies ⋅ Show All (11)

  • 
    Sanjay Sood replied

    Yes, they are forced to check their results in the light of these discrepancies but the original results are expected to hold. The best way to understand higher dimensional space is to assume thatYes, they are forced to check their results in the light of these discrepancies but the original results are expected to hold. The best way to understand higher dimensional space is to assume that our (3+1) dimensional de Sitter space is the boundary of the 5d space through which these neutrinos might be taking the short cut. This analogy takes advantage of the famous AdS/CFT conjecture where a flat (3+1) dimensional Minkowski spacetime is the boundary to the 5 dimensional Anti De Sitter space. One defines the strongly coupled Super symmetric Yang-Mills theory on the boundary (3+1) dimensional flat space and the 5 dimensional AdS space contains is the weakly coupled dual super gravity theory due to the super strings in that space.

    Mar 2, 2012
• Dipankar Das

  Is there any problem with a fermion singlet within the Standard Model?

  By 'singlet' I mean SU(2) singlet, i.e. a charged fermion without its partner. Is there any theoretical drawback? As I think, it will have no coupling with the Higgs, since Higgs is not needed toBy 'singlet' I mean SU(2) singlet, i.e. a charged fermion without its partner. Is there any theoretical drawback? As I think, it will have no coupling with the Higgs, since Higgs is not needed to give mass to it. Will it be phenomenologically uninteresting?

  Recent replies ⋅ Show All (5)

  • 
    David Schaich replied

    Jens, you are of course correct, but I believe the question proposed novel SU(2)-singlets *without* SU(2)-doublet partners.

    Mar 1, 2012
• C.AmarEshwar Prasad

  Can Neutrons be accelerated by means of any energy ?

  Yes,Neutrons can be accelerated with help of thermal energy
• Frank Lucatelli

  The Origins of Classical Matter - Part I: Neutrinos and Part II: Electrons, Photons and Positrons

  Frank J. Lucatelli and Thomas L. Kopinski.pdf

  Recent replies ⋅ Show All (3)

  • 
    Nenad Delic replied

    There is trouble with the law of conservation of energy. Maybe the dark matter hidden in the structure of the electron or quark.

    Feb 24, 2012
• Raul Alvarez

  Does someone know under which conditions an uncharged fermion can exist in a general spacetime? What about electrically charged fermions?

  I would like to add a missing ingredient into the discussion above. It is well known for the geometers that due to topological obstructions it is impossible to construct a coherent theory ofI would like to add a missing ingredient into the discussion above. It is well known for the geometers that due to topological obstructions it is impossible to construct a coherent theory of uncharged fermions in a general four dimentional riemannian manifold. In contrast, a theory of U(1)-charged fermions it's perfectly well defined in such manifolds. For a quick reference on this topic see: http://en.wikipedia.org/wiki/Spin_structure Does someone knows what's the situation in the Lorentzian case? (that's what i mean by a "general spacetime")

  Recent replies ⋅ Show All (4)

  • 
    Andrew James Bruce replied

    @Raul Alvarez: Thank you for the reference. I think this is something I should know a little more about than I actually do!

    Feb 23, 2012
• Ahmad Ryan

  Matter and anti-matter!

  When a matter and anti-matter collides, they annihilate leaving nothing but pure energy. And as far as I know, they differ only in terms of the type of the charge which they carry. But just becauseWhen a matter and anti-matter collides, they annihilate leaving nothing but pure energy. And as far as I know, they differ only in terms of the type of the charge which they carry. But just because two particles have different charges, it is the electrical potential energy which should be released, why and how does even mass get converted into energy???

  Recent replies ⋅ Show All (20)

  • 
    Sunny Kataria replied

    @James Must say You have good insights and clear understanding of QED. Though I am biologist by profession I enjoyed the clear discussions here. I would like to discuss more on this topic and@James Must say You have good insights and clear understanding of QED. Though I am biologist by profession I enjoyed the clear discussions here. I would like to discuss more on this topic and symmetries as soon as I find some quantum of time.

    Feb 11, 2012