scholarly journals Schwinger’s approach to Einstein’s gravity and beyond

2014 ◽  
Vol 92 (9) ◽  
pp. 964-967 ◽  
Author(s):  
K.A. Milton
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
20Th Century ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Space Time ◽  
Gravity Theory ◽  
Curved Space ◽  
Theoretical Physicist ◽  
The Subject

J. Schwinger (1918–1994), founder of renormalized quantum electrodynamics, was arguably the leading theoretical physicist of the second half of the 20th century. Thus it is not surprising that he made contributions to gravity theory as well. His students made major impacts on the still uncompleted program of constructing a quantum theory of gravity. Schwinger himself had no doubt of the validity of general relativity, although he preferred a particle physics viewpoint based on gravitons and the associated fields, and not the geometrical picture of curved space–time. This article provides a brief summary of his contributions and attitudes toward the subject of gravity.

scholarly journals STEPHEN HAWKING: SPACE, TIME AND QUANTA

2020 ◽  
Author(s):  
Mauro Carfora
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
Space Time ◽  
Stephen Hawking

A brief introduction to the scientic work of Stephen Hawking and to his contributions to our understanding of the interplay between general relativity and quantum theory.

Zum Übergang von der Wellenoptik zur geometrischen Optik in der allgemeinen Relativitätstheorie

1967 ◽  
Vol 22 (9) ◽  
pp. 1328-1332 ◽  
Author(s):  
Jürgen Ehlers
Keyword(s):  
General Relativity ◽  
Maxwell Equations ◽  
Expansion Method ◽  
Flat Space ◽  
Space Time ◽  
Moving Medium ◽  
Formal Similarity ◽  
Curved Space ◽  
Optical Metric ◽  
Series Expansion Method

The transition from the (covariantly generalized) MAXWELL equations to the geometrical optics limit is discussed in the context of general relativity, by adapting the classical series expansion method to the case of curved space time. An arbitrarily moving ideal medium is also taken into account, and a close formal similarity between wave propagation in a moving medium in flat space time and in an empty, gravitationally curved space-time is established by means of a normal hyperbolic optical metric.

scholarly journals On the emergence of the structure of physics

2018 ◽  
Vol 376 (2118) ◽  
pp. 20170231 ◽  
Author(s):  
S. Majid
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
Quantum Gravity ◽  
Recent Work ◽  
Space Time ◽  
Quantum Space ◽  
Conceptual Level ◽  
Theme Issue ◽  
Self Duality ◽  
Born Reciprocity

We consider Hilbert’s problem of the axioms of physics at a qualitative or conceptual level. This is more pressing than ever as we seek to understand how both general relativity and quantum theory could emerge from some deeper theory of quantum gravity, and in this regard I have previously proposed a principle of self-duality or quantum Born reciprocity as a key structure. Here, I outline some of my recent work around the idea of quantum space–time as motivated by this non-standard philosophy, including a new toy model of gravity on a space–time consisting of four points forming a square. This article is part of the theme issue ‘Hilbert’s sixth problem’.

scholarly journals Towards Unification of General Relativity and Quantum Theory: Dendrogram Representation of the Event-Universe

2021 ◽  
Author(s):  
Andrei Khrennikov ◽  
Oded Shor ◽  
Benninger Felix
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
Spin Glasses ◽  
Disordered Systems ◽  
Space Time ◽  
Unified Field Theory ◽  
Real Representation ◽  
Finite Tree ◽  
Bohm Potential ◽  
The Universe

Following Smolin, we proceed to unification of general relativity and quantum theory by operating solely with events, i.e., without appealing to physical systems and space-time. The universe is modelled as a dendrogram (finite tree) expressing the hierarchic relations between events. This is the observational (epistemic) model; the ontic model is based on p-adic numbers (infinite trees). Hence, we use novel mathematics—not only space-time but even real numbers are not in use. Here, the p-adic space (which is zero dimensional) serves as the base for the holographic image of the universe. In this way our theory relates to p-adic physics; in particular, p-adic string theory and complex disordered systems (p-adic representation of Parisi matrix for spin glasses). Our Dendrogramic-Holographic (DH) theory matches perfectly with the Mach’s principle and Brans-Dicke theory. We found surprising informational interrelation between the fundamental constants, h, c, G, and their DH-analogues, h(D), c(D), G(D). DH-theory is part of Wheeler’s project on the information restructuring of physics. It is also a step towards the Unified Field theory. The universal potential V is nonlocal, but this is relational DH-nonlocality. V can be coupled to the Bohm quantum potential by moving to the real representation. This coupling enhanced the role of the Bohm potential.

Electrodynamics in curved space-time: Free-space longitudinal wave propagation

2019 ◽  
Vol 32 (3) ◽  
pp. 282-291 ◽  
Author(s):  
Ole Keller ◽  
Lee M. Hively
Keyword(s):  
Scalar Field ◽  
Longitudinal Wave ◽  
Free Space ◽  
Quantum Electrodynamics ◽  
Wave Theory ◽  
Space Time ◽  
Metric Tensor ◽  
Curved Space ◽  
Magnetization Density ◽  
General Relativistic

Jiménez and Maroto [Phys. Rev. D 83, 023514 (2011)] predicted free-space, longitudinal electrodynamic waves in curved space-time, if the Lorenz condition is relaxed. A general-relativistic extension of Woodside’s electrodynamics [Am. J. Phys. 77, 438 (2009)] includes a dynamical, scalar field in both the potential- and electric/magnetic-field formulations without mixing the two. We formulate a longitudinal-wave theory, eliminating curvature polarization, magnetization density, and scalar field in favor of the electric/magnetic fields and the metric tensor. We obtain a wave equation for the longitudinal electric field for a spatially flat, expanding universe with a scale factor. This work is important, because: (i) the scalar- and longitudinal-fields do not cancel, as in classical quantum electrodynamics; and (ii) this new approach provides a first-principles path to an extended quantum theory that includes acceleration and gravity.

Strings in curved space-time: Virasoro algebra in the classical and quantum theory

1987 ◽  
Vol 35 (6) ◽  
pp. 1917-1938 ◽  
Author(s):  
Ratindranath Akhoury ◽  
Yasuhiro Okada
Keyword(s):  
Quantum Theory ◽  
Virasoro Algebra ◽  
Space Time ◽  
Curved Space

A New Test of the Theory of General Relativity

1979 ◽  
Vol 3 (5) ◽  
pp. 364-364
Author(s):  
D. F. Crawford
Keyword(s):  
General Relativity ◽  
Space Time ◽  
Review Article ◽  
Curved Space ◽  
Gravitational Theories ◽  
Photon Frequency

It has been recently suggested (Crawford 1979) that there is an interaction between a photon and curved space-time that can be observed as a redshift of the photon frequency. Since the amount of the redshift is a function of the curvature it may be used to discriminate between gravitational theories. This is easily done using the parametrized post-Newtonian (PPN) limit fully described in the review article by Will (1972).

scholarly journals Space–Time Physics in Background-Independent Theories of Quantum Gravity

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 251
Author(s):  
Martin Bojowald
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
Quantum Gravity ◽  
Riemannian Geometry ◽  
Loop Quantum Gravity ◽  
Space Time ◽  
Time Analysis ◽  
Complete Space ◽  
Background Independence ◽  
Starting Point

Background independence is often emphasized as an important property of a quantum theory of gravity that takes seriously the geometrical nature of general relativity. In a background-independent formulation, quantum gravity should determine not only the dynamics of space–time but also its geometry, which may have equally important implications for claims of potential physical observations. One of the leading candidates for background-independent quantum gravity is loop quantum gravity. By combining and interpreting several recent results, it is shown here how the canonical nature of this theory makes it possible to perform a complete space–time analysis in various models that have been proposed in this setting. In spite of the background-independent starting point, all these models turned out to be non-geometrical and even inconsistent to varying degrees, unless strong modifications of Riemannian geometry are taken into account. This outcome leads to several implications for potential observations as well as lessons for other background-independent approaches.

Sign in / Sign up

Export Citation Format

Share Document