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John Swain

Publications and source records attributed to John Swain.

At least 19 recordsLinked to original sources
arXiv2022

General Relativity versus Dark Matter for rotating galaxies

A very general class of axially-symmetric metrics in general relativity (GR) that includes rotations is used to discuss the dynamics of rotationally-supported galaxies. The exact vacuum solutions of the Einstein equations for this extended Weyl class of metrics allow us to deduce rigorously the following: (i) GR rotational velocity always exceeds the Newtonian velocity (thanks to Lenz's law in GR); (ii) A non-vanishing intrinsic angular momentum ($J$) for a galaxy demands the asymptotic constancy of the Weyl (vectorial) length parameter ($a$) -a behavior identical to that found for the Kerr metric; (iii) Asymptotic constancy of the same parameter $a$ also demands a plateau in the rotational velocity. Unlike the Kerr metric, the extended Weyl metric can and has been continued within the galaxy and it has been shown under what conditions Gauß \&\ Ampére laws emerge along with Ludwig's extended GEM theory with its attendant non-linear rate equations for the velocity field. Better estimates (than that from the Newtonian theory) for the escape velocity of the Sun and a reasonable rotation curve \&\ $J$ for our own galaxy has been presented.

gr-qc↗
arXiv2014

Measuring Newton's Gravitational Constant With a Gravitational Oscillator

Newton's gravitational constant G, which determines the strength of gravitational interactions both in Newton's theory and in Einstein's General Relativity, is the least well known of all the fundamental constants. Given its importance, and with recent disparities between experimental measurements, a new approach is suggested. It is based on a purely gravitational oscillator without any non-gravitational restoring forces. The suggested technique is based on the oscillation period of a test mass oscillating through a hole bored in a solid sphere in free space, or, equivalently, in orbit. The period of oscillation depends only on the density of the solid sphere, providing a method with systematic errors different from terrestrial approaches to the determination of G. Deviations from standard Newtonian gravity and the equality of gravitational and inertial mass can also be searched for.

gr-qc↗
arXiv2014

Materials Bound by Non-Chemical Forces: External Fields and the Quantum Vacuum

We discuss materials which owe their stability to external fields. These include: 1) external electric or magnetic fields, and 2) quantum vacuum fluctuations in these fields induced by suitable boundary conditions (the Casimir effect). Instances of the first case include the floating water bridge and ferrofluids in magnetic fields. An example of the second case is taken from biology where the Casimir effect provides an explanation of the formation of stacked aggregations or "rouleaux" by negatively charged red blood cells. We show how the interplay between electrical and Casimir forces can be used to drive self-assembly of nano-structured materials, and could be generalized both as a probe of Casimir forces and as a means of manufacturing nanoscale structures. Interestingly, all the cases discussed involve the generation of the somewhat exotic negative pressures. We note that very little is known about the phase diagrams of most materials in the presence of external fields other than those represented by the macroscopic scalar quantities of pressure and temperature. Many new and unusual states of matter may yet be undiscovered.

physics.gen-ph↗
arXiv2011

Particles, Fields, Pomerons and Beyond

This paper is a set of musings on what particles really are -- something one all too often as a particle physicist assumes is pretty well-established. The initial motivation for these thoughts comes from a question that I always ask Alberto Santoro whenever I see him which is "What exactly is a pomeron?". I argue that the concept of a particle that we normally have is really quite far from reality and that there could be deep physics in reconsidering very carefully exactly what we mean by particles. Perhaps one of the great coming challenges is not simply to "find more particles and measure their couplings" but to revisit the very concept itself of a particle, and that a good place to do this may well be very strongly interacting theories like QCD and in very forward scattering and the study of objects like pomerons.

hep-ph↗
arXiv2011

Simplicial Gravity and Strings

String theory, as a theory containing quantum gravity, is usually thought to require more dimensions of spacetime than the usual 3+1. Here I argue on physical grounds that needing extra dimensions for strings may well be an artefact of forcing a fixed flat background space. I also show that discrete simplicial approaches to gravity in 3+1 dimensions have natural string-like degrees of freedom which are inextricably tied to the dynamical space in which they evolve. In other words, if simplicial approaches to 3+1 dimensional quantum gravity do indeed give consistent theories, they may essentially contain consistent background-independent string theories.

gr-qc↗
arXiv2010

Black Holes and the Strong CP Problem

The strong CP problem is that SU(3) gauge field instantons naturally induce a CP violating term in the QCD Lagrangian which is constrained by experiment to be very small for no obvious reason. We show that this problem disappears if one assumes the existence of at least one black hole somewhere in the universe. The argument is reminiscent of Dirac's argument for the quantization of charge, in which the existence of one monople anywhere in the universe suffices to require the quantization of electric charge everywhere.

gr-qc↗
arXiv2010

Gravitatomagnetic Analogs of Electric Transformers

Linearized general relativity admits a formulation in terms of gravitoelectric and gravitomagnetic fields that closely parallels the description of the electromagnetic field by Maxwell's equations. For steady mass currents, this formalism has been used to understand gravitomagnetic effects like the Lense-Thirring dragging of inertial frames. For time-varying mass-energy currents, the analog of Faraday's law suggests new effects based on the gravitational equivalent of a transformer where such currents take the place of electrical currents. New experimental possibilities are suggested including a novel coupling mechanism of electromagnetism to gravity, new tests of general relativity in the ultrarelativistic limit using particle beams in the LHC, and searches for a materials exhibiting the gravitational analog of ferromagnetism.

gr-qc↗
arXiv2008

Exotic Statistics for Ordinary Particles in Quantum Gravity

Objects exhibiting statistics other than the familiar Bose and Fermi ones are natural in theories with topologically nontrivial objects including geons, strings, and black holes. It is argued here from several viewpoints that the statistics of ordinary particles with which we are already familiar are likely to be modified due to quantum gravity effects. In particular, such modifications are argued to be present in loop quantum gravity and in any theory which represents spacetime in a fundamentally piecewise-linear fashion. The appearance of unusual statistics may be a generic feature (such as the deformed position-momentum uncertainty relations and the appearance of a fundamental length scale) which are to be expected in any theory of quantum gravity, and which could be testable.

gr-qc↗
arXiv2006

On the Possibility of Large Upconversions and Mode Coupling between Frohlich States and Visible Photons in Biological Systems

At least two significant roles for large scale quantum coherence in living systems have been suggested: Herbert Fröhlich's coherent excitations of nonlinearly coupled ensembles of large polarizable molecules, with frequencies in the microwave region, and Fritz Popp's coherent visible photon emission arising from metabolically active cells. The large difference in frequencies has made it difficult to see these two phenomena as being linked. Here a case is made for a potentially large coupling between these modes, and suggestions are made for the biological roles played by these coherent excitations.

physics.bio-ph↗
arXiv2005

Entropy and Area in Loop Quantum Gravity

Black hole thermodynamics suggests that the maximum entropy that can be contained in a region of space is proportional to the area enclosing it rather than its volume. I argue that this follows naturally from loop quantum gravity and a result of Kolmogorov and Bardzin' on the the realizability of networks in three dimensions. This represents an alternative to other approaches in which some sort of correlation between field configurations helps limit the degrees of freedom within a region. It also provides an approach to thinking about black hole entropy in terms of states inside rather than on its surface. Intuitively, a spin network complicated enough to imbue a region with volume only lets that volume grow as quickly as the area bounding it.

gr-qc↗
arXiv2005

Gluino Air Showers as a Signal of Split Supersymmetry

It has been proposed recently that, within the framework of split Supersymmetry, long lived gluinos generated in astrophysical sources could be detected using the signatures of the air showers they produce, thus providing a lower bound for their lifetime and for the scale of SUSY breaking. We present the longitudinal profile and lateral spread of $G$-hadron induced extensive air showers and consider the possibility of measuring them with a detector with the characteristics of the Pierre Auger Observatory.

hep-ph↗
arXiv2004

High Energy Physics in the Atmosphere: Phenomenology of Cosmic Ray Air Showers

The properties of cosmic rays with energies above 10**6 GeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review we summarize the phenomenology of these giant air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra high energies, and discuss the prospects for insights into forward physics at the LHC. We also describe the main electromagnetic processes that govern the longitudinal shower evolution, as well as the lateral spread of particles. Armed with these two principal shower ingredients and motivation from the underlying physics, we provide an overview of some of the different methods proposed to distinguish primary species. The properties of neutrino interactions and the potential of forthcoming experiments to isolate deeply penetrating showers from baryonic cascades are also discussed. We finally venture into a terra incognita endowed with TeV-scale gravity and explore anomalous neutrino-induced showers.

hep-ph↗
arXiv2004

On the limiting procedure by which $SDiff(T^2)$ and $SU(\infty)$ are associated

There have been various attempts to identify groups of area-preserving diffeomorphisms of 2-dimensional manifolds with limits of SU(N) as $N\to\infty$. We discuss the particularly simple case where the manifold concerned is the two-dimensional torus $T^2$ and argue that the limit, even in the basis commonly used, is ill-behaved and that the large-N limit of SU(N) is much larger than $SDiff(T^2)$.

hep-th↗
arXiv2004

The Majorana representation of spins and the relation between $SU(\infty)$ and $SDiff(S^2)$

The Majorana representation of spin-$\frac{n}{2}$ quantum states by sets of points on a sphere allows a realization of SU(n) acting on such states, and thus a natural action on the two-dimensional sphere $S^2$. This action is discussed in the context of the proposed connection between $SU(\infty)$ and the group $SDiff(S^2)$ of area-preserving diffeomorphisms of the sphere. There is no need to work with a special basis of the Lie algebra of SU(n), and there is a clear geometrical interpretation of the connection between the two groups. It is argued that they are {\it not} isomorphic, and comments are made concerning the validity of approximating groups of area-preserving diffeomorphisms by SU(n).

hep-th↗
arXiv2004

The Pauli Exclusion Principle, Spin, and Statistics in Loop Quantum Gravity: SU(2) versus SO(3)

Recent attempts to resolve the ambiguity in the loop quantum gravity description of the quantization of area has led to the idea that j=1 edges of spin-networks dominate in their contribution to black hole areas as opposed to j=1/2 which would naively be expected. This suggests that the true gauge group involved might be SO(3) rather than SU(2). We argue that the idea that a version of the Pauli principle is present in loop quantum gravity allows one to maintain SU(2) as the gauge group while still naturally achieving the desired suppression of spin-1/2 punctures. Such an idea can be motivated by arguments from geometric quantization even though the SU(2) under consideration does not have the geometrical interpretation of rotations in 3-dimensional space, and its representation labels do not correspond to physical angular momenta. In this picture, it is natural that macroscopic areas come almost entirely from j=1 punctures rather than j=1/2 punctures, and this is for much the same reason that photons lead to macroscopic classically observable fields while electrons do not.

gr-qc↗
arXiv2004

Anisotropies in Ultrahigh Energy Cosmic Rays

The present status of anisotropy studies for the highest energy cosmic rays is presented including the first full sky survey. Directions and prospects for the future are also discussed in light of new statistical methods and the last quantities of data expected in the near future from the Pierre Auger Observatory.

astro-ph↗
arXiv2004

The Pauli Exclusion Principle and SU(2) Versus SO(3) in Loop Quantum Gravity

Recent attempts to resolve the ambiguity in the loop quantum gravity description of the quantization of area has led to the idea that $j=1$ edges of spin-networks dominate in their contribution to black hole areas as opposed to $j=1/2$ which would naively be expected. This suggests that the true gauge group involved might be SO(3) rather than SU(2) with attendant difficulties. We argue that the assumption that a version of the Pauli principle is present in loop quantum gravity allows one to maintain SU(2) as the gauge group while still naturally achieving the desired suppression of spin-1/2 punctures. Areas come from $j=1$ punctures rather than $j=1/2$ punctures for much the same reason that photons lead to macroscopic classically observable fields while electrons do not.

gr-qc↗