The theory of gravity is considered from the little group viewpoint. This leads to a theory with a constraint, which is equivalent to general relativity with an arbitrary cosmological term. With this framework (i) the cosmological constant cannot be put into the Lagrangian but it appears as an integration constant. (ii) The gravitational Lagrangian automatically takes the form of a finite polynomial of the metric. (iii) The so-called conformal factor is fixed, which removes an apparent difficulty in carrying out path integrals.

/pdf/the-exchange-of-massless-spin-two-particles-2yjutntyah.pdf

The exchange of massless spin-two particles

In this work we review the theories of origin of matter-antimatter asymmetry in the Universe. The general conditions for achieving baryogenesis and leptogenesis in a CPT conserving field theory have been laid down by Sakharov. In this review we discuss scenarios where a background scalar or gravitational field spontaneously breaks the CPT symmetry and splits the energy levels between particles and anti-particles. Baryon or Lepton number violating processes in proceeding at thermal equilibrium in such backgrounds gives rise to Baryon or Lepton number asymmetry.

Neutrino coupling to cosmological background: A review on gravitational Baryo/Leptogenesis

A wealth of different expressions for the frequency of the Thomas precession (TP) can be found in the literature, with the consequence that this issue has been discussed over a long period of time. It is shown that the correct result was obtained in the works of several authors, which were published more than forty years ago but remained unnoticed against the background of numerous erroneous works. Several TP-related physical paradoxes formulated primarily to disprove the special relativity theory are shown to be fallacious. Different techniques for deriving the correct expression are considered and the reasons for the emergence of the main incorrect expressions for the TP frequency are analyzed.

http://iopscience.iop.org/article/10.1070/PU2006v049n08ABEH005870/pdf

Thomas precession: correct and incorrect solutions

In this paper, we review the theories of origin of matter–antimatter asymmetry in the universe. The general conditions for achieving baryogenesis and leptogenesis in a CPT conserving field theory have been laid down by Sakharov. In this review, we discuss scenarios where a background scalar or gravitational field spontaneously breaks the CPT symmetry and splits the energy levels between particles and antiparticles. Baryon or Lepton number violating processes in proceeding at thermal equilibrium in such backgrounds gives rise to Baryon or Lepton number asymmetry.

Neutrino Coupling to Cosmological Background: a Review on Gravitational Baryo/leptogenesis

The two leading approaches to the challenge of unifying the fundamental interactions, string theory and loop quantum gravity, involve extending space to higher dimensions and discretizing spacetime, respectively. Spontaneous violations of Lorentz symmetry can appear in some versions of the former [1], while the latter can violate Lorentz symmetry explicitly since it entails fixed scales of length or time [2]. Experimental tests of Lorentz symmetry have lately gained tremendous traction with the introduction of a comprehensive effective field theory framework for the study, evaluation and comparison of models for Lorentz violation in all sectors of both general relativity (GR) and the Standard Model of particle physics: the StandardModel extension or SME [3].

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Julian Schwinger

Papers

Spin Precession—A Dynamical Discussion

Precession Tests of General Relativity—Source Theory Derivations