scholarly journals The physical role of gravitational and gauge degrees of freedom in general relativity – II: Dirac versus Bergmann observables and the objectivity of space-time

2006 ◽  
Vol 38 (2) ◽  
pp. 229-267 ◽  
Author(s):  
Luca Lusanna ◽  
Massimo Pauri
Keyword(s):  
General Relativity ◽  
Degrees Of Freedom ◽  
Space Time ◽  
Physical Role

SPACE–TIME ENERGY–MOMENTUM, THE OBSERVER AND UNCERTAINTY IN GENERAL RELATIVITY

2010 ◽  
Vol 19 (14) ◽  
pp. 2353-2359 ◽  
Author(s):  
F. I. COOPERSTOCK ◽  
M. J. DUPRE
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Uncertainty Principle ◽  
Ricci Tensor ◽  
Space Time ◽  
Energy Integral ◽  
New Approach ◽  
Extended Space ◽  
Energy And Momentum

In this essay, we introduce a new approach to energy–momentum in general relativity. Space–time, as opposed to space, is recognized as the necessary arena for its examination, leading us to define new extended space–time energy and momentum constructs. From local and global considerations, we conclude that the Ricci tensor is the required element for a localized expression of energy–momentum to include the gravitational field. We present and rationalize a fully invariant extended expression for space–time energy, guided by Tolman's well-known energy integral for an arbitrary bounded stationary system. This raises fundamental issues which we discuss. The role of the observer emerges naturally and we are led to an extension of the uncertainty principle to general relativity, of particular relevance to ultra-strong gravity.

UNIFIED ELECTROWEAK MODEL BASED ON SPACE–TIME AND ISOSPIN SYMMETRIES

2005 ◽  
Vol 20 (01) ◽  
pp. 175-198 ◽  
Author(s):  
D. SPEHLER ◽  
G. C. MARQUES
Keyword(s):  
Degrees Of Freedom ◽  
Space Time ◽  
Scalar Particles ◽  
Symmetry Breakdown ◽  
Vector Bosons ◽  
Rank 2 ◽  
Electroweak Model ◽  
Spontaneous Symmetry Breakdown ◽  
Internal Degrees Of Freedom

We propose a spinorial approach to the unified electroweak interactions, in which no use is made of spontaneous symmetry breakdown. No scalar particles are needed in order to break the symmetry. No reference is made to gauge symmetry. Our approach stresses the role of space–time and isospin symmetries in the build up of the electroweak model. Internal degrees of freedom, such as isospin, are incorporated in the theory by using spinors carrying isospin indices. All vector bosons are described by a rank 2 field in the spinorial and the isospinorial indices. Leptons are accomodated in a rank 1 spinor field and in a rank 2 isospin field as well. The dynamical variables of the theory are the chiral and isochiral components of these fields.

scholarly journals The Hole Argument in Homotopy Type Theory

2019 ◽  
Vol 50 (4) ◽  
pp. 319-329 ◽  
Author(s):  
James Ladyman ◽  
Stuart Presnell
Keyword(s):  
General Relativity ◽  
Homotopy Type ◽  
Type Theory ◽  
Space Time ◽  
Scientific Representation ◽  
General Covariance ◽  
Hole Argument ◽  
Homotopy Type Theory ◽  
Mathematics And Physics

Abstract The Hole Argument is primarily about the meaning of general covariance in general relativity. As such it raises many deep issues about identity in mathematics and physics, the ontology of space–time, and how scientific representation works. This paper is about the application of a new foundational programme in mathematics, namely homotopy type theory (HoTT), to the Hole Argument. It is argued that the framework of HoTT provides a natural resolution of the Hole Argument. The role of the Univalence Axiom in the treatment of the Hole Argument in HoTT is clarified.

The Sagnac and Hafele–Keating experiments: Two keys to the understanding of space–time physics in the vicinity of the Earth

2019 ◽  
Vol 34 (33) ◽  
pp. 1930014
Author(s):  
J. H. Field
Keyword(s):  
General Relativity ◽  
Light Propagation ◽  
Theoretical Calculations ◽  
Space Time ◽  
Time Dilation ◽  
Sagnac Effect ◽  
Preferred Frame ◽  
The Earth ◽  
Measured Time

The role of preferred frames for light propagation and time dilation in the region of a massive, spherical, gravitating bodies, where according to general relativity, space–time curvature is described by the Schwarzschild metric equation, is discussed in the context of the Sagnac effect (for light propagation) and the Hafele–Keating experiment (for time dilation). Predictions for both translational and rotational motion relative to the preferred frame are calculated up to order [Formula: see text]. Different published theoretical calculations of the Sagnac effect are critically reviewed. The conflation in the literature of measured time differences in Sagnac experiments (a classical order [Formula: see text] effect) and time dilation (a relativistic order [Formula: see text] effect) are also discussed.

scholarly journals Gravitational breathing memory and dual symmetries

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Ali Seraj
Keyword(s):  
General Relativity ◽  
Gauge Theory ◽  
Scalar Field ◽  
Memory Effects ◽  
Balance Equations ◽  
Symmetry Principle ◽  
Dual Formulation ◽  
Physical Role ◽  
Asymptotic Symmetries

Abstract Brans-Dicke theory contains an additional propagating mode which causes homogeneous expansion and contraction of test bodies in transverse directions. This “breathing” mode is associated with novel memory effects in addition to those of general relativity. Standard tensor mode memories are related to a symmetry principle: they are determined by the balance equations corresponding to the BMS symmetries. In this paper, we show that the leading and subleading breathing memory effects are determined by the balance equations associated with the leading and “overleading” asymptotic symmetries of a dual formulation of the scalar field in terms of a two-form gauge field. The memory effect causes a transition in the vacuum of the dual gauge theory. These results highlight the significance of dual charges and the physical role of overleading asymptotic symmetries.

scholarly journals A Teleparallel Type Theory for Massless Spin 2 Fields

2020 ◽  
Author(s):  
José Wadih Maluf ◽  
Sérgio Costa Ulhoa
Keyword(s):  
General Relativity ◽  
Electromagnetic Field ◽  
Type Theory ◽  
Degrees Of Freedom ◽  
Symmetric Tensor ◽  
Flat Space ◽  
Space Time ◽  
Two Degrees Of Freedom ◽  
Curved Space ◽  
Massless Spin

We present the Lagrangian and Hamiltonian formulations of a theory for spin 2 fields. The construction is developed in flat space-time. The construction in curved space-time is conceptually straightforward, although it is not unique. The theory is based on a symmetric tensor $S_{\mu\nu}$, contains two degrees of freedom of radiation, is motivated by the teleparallel formulation of general relativity, and displays a certain resemblance with Maxwell's theory for the electromagnetic field.

scholarly journals Quartet-Metric Gravity and Dark Components of the Universe

2018 ◽  
Vol 47 ◽  
pp. 1860101 ◽  
Author(s):  
Y. F. Pirogov
Keyword(s):  
General Relativity ◽  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Wide Spectrum ◽  
Space Time ◽  
Emergent Gravity ◽  
Gravity Fields ◽  
Higgs Fields ◽  
The Universe

In the report there are presented the general frameworks for the quartet-metric gravity based on the two main principles. First, there exist in space-time the distinct dynamical coordinates, given by a scalar quartet, playing the role of the Higgs fields for gravity. Second, the physical gravity fields arising due to the spontaneous symmetry breaking serve as the dark components of the Universe. It is argued that the mere admixture to metric of the scalar quartet may give rise to an extremely wide spectrum of the emergent gravity phenomena beyond General Relativity (GR). Further developing the proposed frameworks to find out the next-to-GR theory of gravity is a challenge.

Do Writing Directions Influence How People Map Space onto Time?

2018 ◽  
Vol 77 (4) ◽  
pp. 173-184
Author(s):  
Wenxing Yang ◽  
Ying Sun
Keyword(s):  
Mental Representations ◽  
Space Time ◽  
Horizontal Axis ◽  
Causal Role ◽  
Writing Systems ◽  
Temporal Cognition ◽  
Japanese Speakers ◽  
Psychological Experiments ◽  
Vertical Up

Abstract. The causal role of a unidirectional orthography in shaping speakers’ mental representations of time seems to be well established by many psychological experiments. However, the question of whether bidirectional writing systems in some languages can also produce such an impact on temporal cognition remains unresolved. To address this issue, the present study focused on Japanese and Taiwanese, both of which have a similar mix of texts written horizontally from left to right (HLR) and vertically from top to bottom (VTB). Two experiments were performed which recruited Japanese and Taiwanese speakers as participants. Experiment 1 used an explicit temporal arrangement design, and Experiment 2 measured implicit space-time associations in participants along the horizontal (left/right) and the vertical (up/down) axis. Converging evidence gathered from the two experiments demonstrate that neither Japanese speakers nor Taiwanese speakers aligned their vertical representations of time with the VTB writing orientation. Along the horizontal axis, only Japanese speakers encoded elapsing time into a left-to-right linear layout, which was commensurate with the HLR writing direction. Therefore, two distinct writing orientations of a language could not bring about two coexisting mental time lines. Possible theoretical implications underlying the findings are discussed.

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