## Thursday, September 26, 2019

### Theoretical physics questions answered Essay Example | Topics and Well Written Essays - 3750 words

Theoretical physics questions answered - Essay Example (see answer-3) The remaining questions are about the rest of the paper, it would be sufficient for me if you could quote a book and chapter where I could find an answer to the respective question: -page 5: what do you mean by "carry no energy or momentum however ha energy-momentum" This means that massless particles are meaningless in Newtonian mechanics because they carry no energy or momentum and cannot sustain any force. Now, the relativistic expression for energy and momentum which is: however allows for non-zero energy-momentum for a massless particle when and this requires |v| 1. Furthur, in order to relate the energy E and momentum p we can assume that the relation p2 = m2 is valid for m = 0, and so, a massless particle's energy E and momentum p are related by E = |p|. page 7: I do not understand the sentence: "mediator has to be given on-zero spin" This actually wants to say that in order to accommodate the observed properties of the long-range electromagnetic and gravitational interactions, we also need to give the mediator a on-zero spin. However, this is non-trivial. _ page 8: why does the P operator transform under the fundamental This is an intrinsic requirement in any space-time study dealing with real vector spaces. Here 'P' is the orthogonal parameter that is subject to fundamental representation whereas U(A) is the unitary parameter representing the Lorentz group. This stands for transformations of the vector space that preserve the length of vectors. There are two vectors having zero scalar product in one reference frame which will remain orthogonal in the rotated frame. Remember space-time is itself a fundamental dynamic variable. - page 9 : eq 14: it is not clear to me why it is sufficient to consider the... This means that massless particles are meaningless in Newtonian mechanics because they carry no energy or momentum and cannot sustain any force. Now, the relativistic expression for energy and momentum which is: however allows for non-zero energy-momentum for a massless particle when and this requires |v| 1. This actually wants to say that in order to accommodate the observed properties of the long-range electromagnetic and gravitational interactions, we also need to give the mediator a on-zero spin. However, this is non-trivial. This is an intrinsic requirement in any space-time study dealing with real vector spaces. Here 'P' is the orthogonal parameter that is subject to fundamental representation whereas U(A) is the unitary parameter representing the Lorentz group. This stands for transformations of the vector space that preserve the length of vectors. There are two vectors having zero scalar product in one reference frame which will remain orthogonal in the rotated frame. Remember space-time is itself a fundamental dynamic variable. The irreps corresponding to the massless particles are found using the irreps of the little group for the massless particles and thus this is a better option. This little group is actually isotropy group and is a subgroup of the Poincare. no "internal Yang-Mills index" ^a which in our case transforms under space-time SO(1,3) rather than internal