Anamitra Palit
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 Dec 2 comment On Parallel Transport Quoting Ron Maimon:"It ends up in nearly exactly the same direction as it was when you start the parallel transport"---in such a situation if you move back to A the vector does not turn by alpha. It turns by a much smaller amount! On removing the triangle the vector in the initial and the final situation (at A) make a very small angle. If the triangle is there it turns by 90 degrees after looping round Dec 2 comment On Parallel Transport Only if you consider a geodesic the an infinitesimally think space round it and parallel to it is nearly flat--the tangent vector propagates parallel to itself Dec 2 awarded Caucus Dec 2 asked On Parallel Transport Nov 14 awarded Yearling Sep 25 comment Interaction between a Pair of Particles @DavidZaslavsky: The last editing to the question was done 11 hours ago and the last editing to one of the answers was worked out 8 hours ago. And suddenly(1 hour ago) you have accused me of bumping the question. That's quite strange. Sep 25 comment Interaction between a Pair of Particles A slightly Generalized Case in absence of annihilation of mass:Initial States:Particle $A:(E_A,\vec{p}_A,m_A);Particle B:(E_B,\vec{p}_B,m_B)$. Final States:$A:(E_A+E,\vec{p}_A+\vec{p},m_A+m);Particle B:(E_B-E,\vec{p}_B-\vec{p},m_B-m)$.Total rest mass is assumed to be constant;"m" may be positive or negative.Instead of relation (5) in answer we have:$EE_{tot}=\vec{p}.\vec{p}_{tot}+mm_{tot}$;where $m_{tot}=m_A+m_B$.The transferred "packet" is not necessarily on the mass shell. $Relation{\;} (10){\;\;}incidentally{\;\;} remains{\;\;\;\;} unchanged{\;\;\;}!$ Sep 25 comment Interaction between a Pair of Particles Whatever you do in particle physics is in consistency with the notions of Relativity.So relativity by itself should be in a position strong enough to predict or rather encompass in its broadest perspectives the results of scattering phenomena in particle physics.These results are consistent with the formula $E^2=p^2+m_0^2$ and of course with the laws of energy and momentum conservation. Nothing should go against the said formula and Laws having the veto power Sep 25 comment Interaction between a Pair of Particles @dmckee: In case you have implied the interaction between a pair of particles having different rest masses there is no problem. The mass terms on the RHS of (1) and (2) are different. The same different mass terms occur on the RHS of (3) and (4). when you subtract (3) from (4) and use the relations (1) and (2) the individual mass terms do cancel and relations (5) (6) etc remain unchanged.Relation (1) considers the release of energy (and momentum) by the particle B. The mass term is not there(it cancels out) Sep 25 comment Interaction between a Pair of Particles @dmckee:The transmitted packet is "off the mass shell".The relation $E\approx pc{\;\;}Or,\triangle E\approx c\triangle p$---(A) is valid for high speed real particles especially those having speed close to the value of light(and less than it). Such particles lie on the mass shell. Relation (A) does not apply to packets of energy transfer(virtual particles).Virtual particles,incidentally, do not lie on the mass shell.The relation coming from my calculations relates to virtual particles and are quite justified. Sep 25 revised Interaction between a Pair of Particles added 127 characters in body Sep 25 revised Interaction between a Pair of Particles deleted 77 characters in body Sep 25 revised Interaction between a Pair of Particles added 212 characters in body Sep 25 revised Interaction between a Pair of Particles edited tags Sep 25 revised Interaction between a Pair of Particles added 1 characters in body Sep 24 revised Interaction between a Pair of Particles added 306 characters in body Sep 24 answered Interaction between a Pair of Particles Sep 24 comment Interaction between a Pair of Particles For any type of energy reception $\triangle E<<\triangle p$ . Discrete transfer favors such a condition.For an apparently continuous transmission each "packet " should comply with relation (4) (5) or (6) wrt to the frame $K_i$ concerned Sep 24 answered Interaction between a Pair of Particles Sep 22 comment Interaction between a Pair of Particles In the relation $EdE=\vec{p}\cdot d\vec{p}$ we may allow the magnitude of $\vec{p}$ to tend to zero. The RHS of the first relation tends to zero but the LHS will not go off to zero