2006/06/27 by T. Padmanabhan, Τ. Padmanabhan · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Classical mechanics #Cosmology and Gravitation Theories #Geometry #Geophysics and Gravity Measurements #Holography #Optics #Perspective (graphical) #Physics #Relativity and Gravitational Theory #Theoretical physics #astro-ph #gr-qc #hep-th
paper · pdf · doi:10.1142/s0218271806009029
published as Int.J.Mod.Phys. D15 (2006) 1659-1676 · Plenary talk at the International Conference on Einstein's Legacy in the New Millennium, December 15 - 22, 2005, Puri, India; to appear in the Proceedings to be published in IJMPD; 16 pages; no figures
arxiv created 2006/06/27 · openalex publication_date 2006/10/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A general paradigm for describing classical (and semiclassical) gravity is presented. This approach brings to the center-stage a holographic relationship between the bulk and surface terms in a general class of action functionals and provides a deeper insight into several aspects of classical gravity which have no explanation in the conventional approach. After highlighting a series of unresolved issues in the conventional approach to gravity, we show that (i) principle of equivalence, (ii) general covariance and (iii) a reasonable condition on the variation of the action functional, suggest a generic Lagrangian for semiclassical gravity of the form L = Q a bcd R a bcd with ∇ b Q a bcd = 0. The expansion of Q a bcd in terms of the derivatives of the metric tensor determines the structure of the theory uniquely. The zeroth order term gives the Einstein–Hilbert action and the first order correction is given by the Gauss–Bonnet action. Any such Lagrangian can be decomposed into surface and bulk terms which are related holographically. The equations of motion can be obtained purely from a surface term in the gravity sector. Hence the field equations are invariant under the transformation T ab → T ab + λg ab and gravity does not respond to the changes in the bulk vacuum energy density. The cosmological constant arises as an integration constant in this approach. The implications are discussed.