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At least 397 records · Page 22Linked to original sources
arXiv2013

Stringy Corrections to the Classical Tests of General Relativity

String theory imposes modifications to Einstein's equations of classical general relativity. Consequently, we calculate the additional corrections to the classical tests: the perihelion precession of Mercury, the deflection of light rays by the sun, and the gravitational redshift which should be present if these modified equations hold. In each case, we determine --- quite consistently with expectations --- that the stringy effects are much too small to be measured.

hep-th↗
arXiv2013

String Theory has no Isotropic Solution for the Modified Einstein's Equations without the Dilaton

We investigate the modification to Einstein's vacuum field equations which is imposed by string theory when the dilaton field is ignored. Including the cosmological constant in all calculations, we prove that such a theory of gravity admits no static isotropic solution. We then show that any isotropic solution of the equations in question must necessarily be static, therefore proving that no isotropic solution exists for this stringy modification to gravity.

hep-th↗
arXiv2013

Mathematical treatment of the homogeneous Boltzmann equation for Maxwellian molecules in the presence of singular kernels

This paper proves the existence of weak solutions to the spatially homogeneous Boltzmann equation for Maxwellian molecules, when the initial data are chosen from the space of all Borel probability measures on R^3 with finite second moments and the (angular) collision kernel satisfies a very weak cutoff condition. Conservation of momentum and energy is also proved for these weak solutions, without resorting to any boundedness of the entropy.

math-ph↗
arXiv2013

SU(2)-Irreducibly covariant and EPOSIC channels

In this paper we introduce EPOSIC channels, a class of SU(2)-covariant quantum channels. We give their definition, a Kraus representation of them, and compute their Choi matrices. We show that these channels form the set of extreme points of all SU(2)-irreducibly covariant channels. We also compute their complementary channels, and their dual maps. As application of these channel, we get a new example of positive map that is not completely positive.

math-ph↗
arXiv2013

Applications of generating function method to the symmetry and the Kronecker products of SU(n) representations

Using the generating function of SU(n) we find the conjugate state of SU(n) basis and we find in terms of Gel'fand basis of SU(3(n-1)) the representation of the invariants of the Kronecker products of SU(n). We find a formula for the number of the elementary invariants of SU(n). We apply our method to the coupling of SU(3) and we find a new expression of the isoscalar of Wigner symbols ($λ10,λ2 μ2; λ3 μ3$).

math-ph↗
arXiv2013

Symmetries of Elko and massive vector fields

This thesis studies the symmetries and phenomenologies of the massive vector fields of indefinite spin with both scalar and spin-one degrees of freedom and Elko. The investigation is conducted by using and extending the quantum field theory formalism developed by Wigner and Weinberg. In particular, we explore the possibility that the W^{\pm} and Z bosons have an additional scalar degree of freedom and show that Elko is a fermionic dark matter candidate. We show that the massive vector fields of indefinite spin are consistent with Poincare symmetry and have physically desirable properties that are absent for their pure spin-one counterpart. Using the new vector fields, the decay of the W^{\pm} and Z bosons to leptons at tree-level are in agreement with the Standard Model (SM) predictions. For higher order scattering amplitudes, the theory has better convergent behaviour than the intermediate vector boson model and the Fermi theory. Elko has the unusual property that it satisfies the Klein-Gordon but not the Dirac equation and has mass dimension one instead of three-half. We show that the Elko fields are local only along a preferred axis and that they violate Lorentz symmetry. Motivated by the results obtained by Ahluwalia and Horvath that the Elko spin-sums are covariant under very special relativity (VSR) transformations, we derive the VSR particle states and quantum fields. We show that the VSR particles can only interact with the SM particles through gravity and massive scalar particles thus making them and hence Elko dark matter candidates.

hep-th↗
arXiv2013

Isospectral deformations of the Dirac operator

We give more details about an integrable system in which the Dirac operator D=d+d^* on a finite simple graph G or Riemannian manifold M is deformed using a Hamiltonian system D'=[B,h(D)] with B=d-d^* + i b. The deformed operator D(t) = d(t) + b(t) + d(t)^* defines a new exterior derivative d(t) and a new Dirac operator C(t) = d(t) + d(t)^* and Laplacian M(t) = d(t) d(t)^* + d(t)* d(t) and so a new distance on G or a new metric on M.

math-ph↗
arXiv2013

Feynman's Path Integral to Ostrogradsky's Hamiltonian for Lagrangians with second derivatives

A calculation is presented that shows that Feynman's path integral implies Ostrogradsky's Hamiltonian for nonsingular Lagrangians with second derivatives. The procedure employs the stationary phase approximation to obtain the limiting change of the wave function per unit time. By way of introduction, the method is applied anew to the case of nonsingular Lagrangians with only first derivatives, but not necessarily quadratic in the velocities. A byproduct of the calculation is an alternate derivation of the Legendre transformation of taking general classical Lagrangians into Hamiltonians. In both the first and second derivative cases, the outcome contains precisely the classical Hamiltonian, which represents the so-called "symbol" of a (not necessarily Hermitean) pseudodifferential operator acting on the wave function at an instant of time. The derivation herein argues for a claim that Feynman's method starts with a classical Lagrangian and ends with a classical Hamiltonian---nonclassical operator-ordering prescriptions in the passage from classical to quantum Hamiltonians require external input, and are generally not inherent in Feynman's path integral formalism.

math-ph↗
arXiv2013

Symmetry Classification of quasi-linear PDE's. II: an exceptional case

This short note completes the symmetry analysis of a class of quasi-linear partial differential equations considered in the previous paper (Nonlinear Dynamics, Vol. 51, 309-316 (2008)): it deals with the presence of an "exceptional" Lie point symmetry, not previously examined, which is admitted only if the involved parameters are fixed by precise relationships. The peculiarity of this symmetry is enhanced by the fact that it leads to a solution relevant in the theory of plasma physics, and also related to the presence of a nontrivial example of a conditional symmetry of weak type.

math-ph↗
arXiv2013

A logical treatment of special relativity, with and without faster-than-light observers

There are three goals of this thesis. First: to present a concise yet accessible description of basic mathematical logic and model theory. Second: to develop an axiomatization of special relativity using only two undefined predicates. Ideally, these axioms should be empirically verifiable and supported by a large body of evidence. Finally: to weaken this axiomatization so as to allow for the existence of faster-than-light observers, which are normally excluded from the theory of special relativity. The modifications to the axiom system should be as slight as possible, and should be motivated by the question: what features of the original axiom system preclude the existence of faster-than-light observers?

math.LO↗
arXiv2013

Generalized Schrödinger semigroups on infinite graphs

With appropriate notions of Hermitian vector bundles and connections over weighted graphs which we allow to be locally infinite, we prove Feynman-Kac-type representations for the corresponding semigroups and derive several applications thereof.

math-ph↗
arXiv2013

An Exact Expression for Photon Polarization in Kerr Geometry

We analyze the transformation of the polarization of a photon propagating along an arbitrary null geodesic in Kerr geometry. The motivation comes from the problem of an observer trying to communicate quantum information to another observer in Kerr spacetime by transmitting polarized photons. It is essential that the observers understand the relationship between their frames of reference and also know how the photon's polarization transforms as it travels through Kerr spacetime. Existing methods to calculate the rotation of the photon polarization (Faraday rotation) depend on choices of coordinate systems, are algebraically complex and yield results only in the weak-field limit. We give a closed-form expression for a parallel propagated frame along an arbitrary null geodesic using Killing-Yano theory, and thereby solve the problem of parallel transport of the polarization vector in an intrinsic, geometrically-motivated fashion. The symmetries of Kerr geometry are utilized to obtain a remarkably compact expression for the geometrically induced phase of the photon's polarization. We show that this phase vanishes on the equatorial plane and the axis of symmetry.

math-ph↗
arXiv2013

A simple construction of integrable Whitham type hierarchies

A simple construction of Whitham type hierarchies in all genera is suggested. Potentials of these hierarchies are written as integrals of hypergeometric type. Possible generalization for universal moduli space is also briefly discussed.

math-ph↗
arXiv2013

Comment on Ashtekar: Generalization of Wigner's Principle

Ashtekar (2013) has illustrated that two of the available roads to testing for time asymmetry can be generalized beyond the structure of quantum theory, to much more general formulations of mechanics. The purpose of this note is to show that a third road to T-violation, which I have called "Wigner's Principle," can be generalized in this way as well.

math-ph↗
arXiv2013

Three Merry Roads to T-Violation

This paper is a tour of how the laws of nature can distinguish between the past and the future, or be T-violating. I argue that, in terms of the basic argumentative structure, there are really just three approaches currently being explored. I show how each is characterized by a symmetry principle, which provides a template for detecting T-violating laws even without knowing the laws of physics themselves. Each approach is illustrated with an example, and the prospects of each are considered in extensions of particle physics beyond the standard model.

math-ph↗
arXiv2013

On non-dissipative and dissipative qubit manifolds

The trajectories of a qubit dynamics over the two-sphere are shown to be geodesics of certain Riemannian or physically-sound Lorentzian manifolds, both in the non-dissipative and dissipative formalisms, when using action-angle variables. Several aspects of the geometry and topology of these manifolds (qubit manifolds) have been studied for some special physical cases.

math-ph↗