scholarly journals Classical Spacetime Structure

2021 ◽  
pp. 33-45
Author(s):  
James Owen Weatherall
Keyword(s):  
Spacetime Structure

Physics, Structure, and Reality

2021 ◽  
Author(s):  
Jill North
Keyword(s):  
Scientific Realism ◽  
Physical Theory ◽  
Scientific Explanation ◽  
Classical Mechanics ◽  
Careful Attention ◽  
Coordinate Systems ◽  
Spacetime Structure ◽  
The World ◽  
Background Assumption ◽  
And Mathematics

How do we figure out the nature of the world from a mathematically formulated physical theory? What do we infer about the world when a physical theory can be mathematically formulated in different ways? Physics, Structure, and Reality addresses these questions, questions that get to the heart of the project of interpreting physics—of figuring out what physics is telling us about the world. North argues that there is a certain notion of structure, implicit in physics and mathematics, that we should pay careful attention to, and that doing so sheds light on these questions concerning what physics is telling us about the nature of reality. Along the way, lessons are drawn for related topics such as the use of coordinate systems in physics, the differences among various formulations of classical mechanics, the nature of spacetime structure, the equivalence of physical theories, and the importance of scientific explanation. Although the book does not explicitly defend scientific realism, instead taking this to be a background assumption, the account provides an indirect case for realism toward our best theories of physics.

scholarly journals Spacetime structure of (3+1)D color fields in high energy nuclear collisions

2021 ◽  
Vol 104 (11) ◽  
Author(s):  
Andreas Ipp ◽  
David I. Müller ◽  
Soeren Schlichting ◽  
Pragya Singh
Keyword(s):  
High Energy ◽  
Nuclear Collisions ◽  
Spacetime Structure

Conventionalism, realism, and spacetime structure

Theoria ◽  
2008 ◽  
Vol 54 (2) ◽  
pp. 81-101 ◽  
Author(s):  
JOHNR. McKIE
Keyword(s):  
Spacetime Structure

COVARIANT ANALYSIS OF NEWTONIAN MULTI-FLUID MODELS FOR NEUTRON STARS I: MILNE–CARTAN STRUCTURE AND VARIATIONAL FORMULATION

2004 ◽  
Vol 13 (02) ◽  
pp. 291-325 ◽  
Author(s):  
BRANDON CARTER ◽  
NICOLAS CHAMEL
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Variational Formulation ◽  
Traditional Approach ◽  
Fluid Models ◽  
Cartan Connection ◽  
Variational Treatment ◽  
Spacetime Structure ◽  
General Kind ◽  
Perfect Fluid Models

This is the first of a series of articles showing how 4 dimensionally covariant analytical procedures developed in the context of General Relativity can be usefully adapted for application in a purely Newtonian framework where they provide physical insights (e.g. concerning helicity currents) that are not so easy to obtain by the traditional approach based on a 3+1 spacetime decomposition. After an introductory presentation of the relevant Milne spacetime structure and the associated Cartan connection, the essential principles are illustrated by application to the variational formulation of simple barotropic perfect fluid models. This variational treatment is then extended to conservative multiconstituent self-gravitating fluid models of the more general kind that is needed for treating the effects of superfluidity in neutron stars.

scholarly journals SPACETIME STRUCTURE AND ELECTROMAGNETISM

2010 ◽  
Vol 25 (20) ◽  
pp. 1705-1721 ◽  
Author(s):  
M. I. WANAS ◽  
SAMAH. A. AMMAR
Keyword(s):  
Geometric Object ◽  
The Other ◽  
Field Theories ◽  
Necessary Condition ◽  
Geometric Representation ◽  
Lagrangian Functions ◽  
Absolute Parallelism ◽  
Spacetime Structure ◽  
Pure Gravity ◽  
Curvature And Torsion

Two Lagrangian functions are used to construct geometric field theories. One of these Lagrangians depends on the curvature of space, while the other depends on curvature and torsion. It is shown that the theory constructed from the first Lagrangian gives rise to pure gravity, while the theory constructed using the second Lagrangian gives rise to both gravity and electromagnetism. The two theories are constructed in a version of absolute parallelism geometry in which both curvature and torsion are, simultaneously, nonvanishing. One single geometric object, W-tensor, reflecting the properties of curvature and torsion, is defined in this version and is used to construct the second theory. The main conclusion is that a necessary condition for geometric representation of electromagnetism is the presence of a nonvanishing torsion in the geometry used.

Axion and dilaton + metric emerge jointly from an electromagnetic model universe with local and linear response behavior

2016 ◽  
Vol 25 (11) ◽  
pp. 1640015
Author(s):  
Friedrich W. Hehl
Keyword(s):  
Scalar Fields ◽  
Relativity Theory ◽  
Electromagnetic Response ◽  
Metric Tensor ◽  
Double Refraction ◽  
Tensor Density ◽  
Electromagnetic Model ◽  
Spacetime Structure ◽  
Riemannian Spacetime ◽  
Axion Field

We take a quick look at the different possible universally coupled scalar fields in nature. Then, we discuss how the gauging of the group of scale transformations (dilations), together with the Poincaré group, leads to a Weyl–Cartan spacetime structure. There the dilaton field finds a natural surrounding. Moreover, we describe shortly the phenomenology of the hypothetical axion field. In the second part of our essay, we consider a spacetime, the structure of which is exclusively specified by the premetric Maxwell equations and a fourth rank electromagnetic response tensor density [Formula: see text] with 36 independent components. This tensor density incorporates the permittivities, permeabilities and the magneto-electric moduli of spacetime. No metric, no connection, no further property is prescribed. If we forbid birefringence (double-refraction) in this model of spacetime, we eventually end up with the fields of an axion, a dilaton and the 10 components of a metric tensor with Lorentz signature. If the dilaton becomes a constant (the vacuum admittance) and the axion field vanishes, we recover the Riemannian spacetime of general relativity theory. Thus, the metric is encapsulated in [Formula: see text], it can be derived from it.

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