Hatsumi Mukai

Propagator, tree-level unitarity and effective nonrelativistic potential for higher-derivative gravity theories in D dimensions

A prescription for computing the propagator for D-dimensional higher-derivative gravity theories, based on the Barnes–Rivers operators, is presented. A systematic study of the tree-level unitarity of these theories is developed and the agreement of their linearized versions with Newton’s law is investigated by computing the corresponding effective nonrelativistic potential. Three-dimensional quadratic gravity with a gravitational Chern–Simons term is also analyzed. A discussion on the issue of light bending within the framework of both D-dimensional quadratic gravity and three-dimensional quadratic gravity with a Chern–Simons term is provided as well.

Scattering of photons by an external gravitational field in the framework of higher-derivative gravity

The scattering of photons by a static gravitational field, treated as an external field, is discussed in the context of gravity with higher derivatives. It is shown that the R 2 sector of the theory does not contribute to the photon scattering, whereas the R 2 sector produces dispersive (energy-dependent) photon propagation.

Effective non-relativistic potential for higher-derivative gravity in D dimensions

An expression for computing the effective non-relativistic potential for higher-derivative gravity in D dimensions is obtained.

Algorithm for Computing the Propagator for Higher Derivative Gravity Theories

A simple algorithm for computing the propagator for higher derivative gravitytheories based on the Barnes–Rivers operators is presented. The prescription isused, among other things, to obtain the propagator for quadratic gravity in anunconventional gauge. We also find the propagator for both gravity and quadraticgravity in an interesting gauge recently baptized the “Einstein” gauge[Hitzer and Dehnen, Int. J. Theor. Phys.36 (1997), 559].

One And The Same Route: Two Outstanding Electrodynamics

We show that the same route that leads to Maxwells electrodynamics leads also to Podolskys electrodynamics, provided we start from Podolskys electrostatic force law instead of the usual Coulombs law.

QUADRATIC GRAVITY IN (2+1)D

Quadratic gravity in (2+1)D, unlike three-dimensional Einsteins gravity, is locally nontrivial and has an extremely well-behaved potential. Here we explore the gravitational properties of a metric generated by a pointlike matter distribution within the context of three-dimensional linearized quadratic gravity. This metric greatly resembles the four-dimensional metric of a straight U(1)-gauge cosmic string in the framework of linearized quadratic gravity. It is found that a gravitational force is exerted on a slowly moving test particle, a feature not present in general relativity in (2+1)D. It is also found that the massive scalar mode does not contribute anything to the gravitational deflection. An explanation for this fact is provided.

Fierz-Pauli higher derivative gravity

We consider a model for gravity in which the linear part of the four-derivative terms oRmn Rmn d4 x and oR2 d4 x are included into the Fierz-Pauli gravitational action. Unitarity is discussed at the tree-level. The issue of the gravitational deflection of a light ray is also considered.

Propagator, tree-level unitarity and effective nonrelativistic potential for three-dimensional higher-derivative gravity augmented by a gravitational Chern-Simons term

Abstract An algorithm for computing the propagator for three-dimensional quadratic gravity with a gravitational Chern–Simons term, based on an extension of the three-dimensional Barnes–Rivers operators, is proposed. A systematic study of the tree-level unitarity of this theory is developed and its agreement with Newtons law is investigated by computing the effective nonrelativistic potential.

A simple prescription for computing the stress - energy tensor

A non-variational technique for computing the stress - energy tensor is presented. The prescription is used, among other things, to obtain the correct field equations for Prasannas highly nonlinear electrodynamics.

Tree-level violation of the equivalence principle

Massive particles of spin 0 and 1 violate the equivalence principle (EP) at the tree level. On the other hand, if these particles are massless, they agree with the EP, which leads us to conjecture that from a semiclassical viewpoint massless particles, no matter what their spin, obey the EP. General relativity predicts a deflection angle of 2.63″ for a nonrelativistic spinless massive boson passing close to the Sun, while for a massive vectorial boson of spin 1 the corresponding deflection is 2.62″.