Author
Ronald J. Riegert
Bio: Ronald J. Riegert is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Scalar field & Conformal symmetry. The author has an hindex of 4, co-authored 4 publications receiving 556 citations.
Papers
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TL;DR: In this article, a covariant, non-local action expandable around flat space is constructed such that the trace of its metric functional derivative has the general form of the trace anomaly (without an R2 term) This is achieved via the introduction of a new fourth-order conformally covariant scalar operator analogous to the second-order operator.
378 citations
TL;DR: In this article, it was shown that the most general spherically symmetric, electrovac solution is static, and hence is stable against spin-0 perturbations.
Abstract: We prove Birkhoff's theorem in conformal gravity: The most general spherically symmetric, electrovac solution is static, and hence absolutely stable against spherically symmetric perturbations. This result goes beyond the zero-energy theorem since it applies even when the solution is not asymptotically flat. On the basis of the known examples, we conjecture that any field theory lacking linearized spin-0 modes possesses a Birkhoff theorem.
166 citations
TL;DR: In this article, it was demonstrated that plane wave solutions of linearized conformal gravity propagate six physical degrees of freedom, corresponding to massless spin-2 and spin-1 ordibary particles and a massless Spin-2 ghost particle.
67 citations
TL;DR: In this paper, the authors consider a theory in which fermionic matter interacts via longe-rage scalar, vector and tensor fields, and show that the scalar and vector couplings for a given fermion must be equal, as is natural in a dimensionally reduced modell.
18 citations
TL;DR: In this article , the authors show that a proposal by Vishwakarma to realize conformal-covariance for the Weyl-Lanczos equation is nonviable.
Abstract: Abstract We show that a proposal by Vishwakarma to realize conformal-covariance for the Weyl-Lanczos equation is nonviable.
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TL;DR: In this article, the authors present a review of the most important aspects of the different classes of modified gravity theories, including higher-order curvature invariants and metric affine.
Abstract: Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology, and astrophysics. Among numerous alternatives to Einstein's theory of gravity, theories that include higher-order curvature invariants, and specifically the particular class of $f(R)$ theories, have a long history. In the last five years there has been a new stimulus for their study, leading to a number of interesting results. Here $f(R)$ theories of gravity are reviewed in an attempt to comprehensively present their most important aspects and cover the largest possible portion of the relevant literature. All known formalisms are presented---metric, Palatini, and metric affine---and the following topics are discussed: motivation; actions, field equations, and theoretical aspects; equivalence with other theories; cosmological aspects and constraints; viability criteria; and astrophysical applications.
4,027 citations
TL;DR: In this article, the authors present explicit models for a symmetry breakdown in the cases of the Weyl (or homothetic) group, the SL(4, R), or the GL(4-R) covering subgroup.
1,474 citations
TL;DR: The heat kernel expansion is a very convenient tool for studying one-loop divergences, anomalies and various asymptotics of the effective action as discussed by the authors, and the heat kernel coefficients are given in terms of several geometric invariants.
1,150 citations
TL;DR: In this article, the effect of trace anomalies for the Nambu-Goldstone boson of broken conformal symmetry in renormalization group flows in four dimensions is analyzed.
Abstract: We discuss some general aspects of renormalization group flows in four dimensions. Every such flow can be reinterpreted in terms of a spontaneously broken conformal symmetry. We analyze in detail the consequences of trace anomalies for the effective action of the Nambu-Goldstone boson of broken conformal symmetry. While the c-anomaly is algebraically trivial, the a-anomaly is “non-Abelian”, and leads to a positive-definite universal contribution to the S-matrix element of 2 → 2 dilaton scattering. Unitarity of the S-matrix results in a monotonically decreasing function that interpolates between the Euler anomalies in the ultraviolet and the infrared, thereby establishing the a-theorem.
898 citations
TL;DR: In this paper, a pedagogical introduction to the classical gravity with torsion, that includes also interaction of torsions with matter fields, is presented, and a comprehensive study of the possibility of a theory for the propagating completely antisymmetric torsION field is presented.
598 citations