1,673 research outputs found
Front Form Spinors in Weinberg-Soper Formalism and Melosh Transformations for any Spin
Using the Weinberg-Soper formalism we construct the front form
spinors. Explicit expressions for the generalised Melosh
transformations up to spin two are obtained. The formalism, without explicitly
invoking any wave equations, reproduces spin one half front-form results of
Melosh, Lepage and Brodsky, and Dziembowski.Comment: 16 Pages, RevTex. We continue to receive reprint requests for this
paper. So we now archive it her
On the spin of gravitational bosons
We unearth spacetime structure of massive vector bosons, gravitinos, and
gravitons. While the curvatures associated with these particles carry a
definite spin, the underlying potentials cannot be, and should not be,
interpreted as single spin objects. For instance, we predict that a spin
measurement in the rest frame of a massive gravitino will yield the result 3/2
with probability one half, and 1/2 with probability one half. The simplest
scenario leaves the Riemannian curvature unaltered; thus avoiding conflicts
with classical tests of the theory of general relativity. However, the quantum
structure acquires additional contributions to the propagators, and it gives
rise to additional phases.Comment: Honorable mention, 2002 Gravity Research Foundation Essay
Interplay of gravitation and linear superposition of different mass eigenstates
The interplay of gravitation and the quantum-mechanical principle of linear
superposition induces a new set of neutrino oscillation phases. These ensure
that the flavor-oscillation clocks, inherent in the phenomenon of neutrino
oscillations, redshift precisely as required by Einstein's theory of
gravitation. The physical observability of these phases in the context of the
solar neutrino anomaly, type-II supernovae, and certain atomic systems is
briefly discussed
Effect of lattice mismatch-induced strains on coupled diffusive and displacive phase transformations
Materials which can undergo slow diffusive transformations as well as fast
displacive transformations are studied using the phase-field method. The model
captures the essential features of the time-temperature-transformation (TTT)
diagrams, continuous cooling transformation (CCT) diagrams, and microstructure
formation of these alloys. In some materials systems there can exist an
intrinsic volume change associated with these transformations. We show that
these coherency strains can stabilize mixed microstructures (such as retained
austenite-martensite and pearlite-martensite mixtures) by an interplay between
diffusive and displacive mechanisms, which can alter TTT and CCT diagrams.
Depending on the conditions there can be competitive or cooperative nucleation
of the two kinds of phases. The model also shows that small differences in
volume changes can have noticeable effects on the early stages of martensite
formation and on the resulting microstructures.
-- Long version of cond-mat/0605577
-- Keywords: Ginzburg-Landau, martensite, pearlite, spinodal decomposition,
shape memory, microstructures, TTT diagram, CCT diagram, elastic compatibilityComment: 10 pages, 13 figures, long version of cond-mat/0605577. Physical
Review B, to appear in volume 75 (2007
Zero Energy of Plane-Waves for ELKOs
We consider the ELKO field in interaction through contorsion with its own
spin density, and we investigate the form of the consequent autointeractions;
to do so we take into account the high-density limit and find plane wave
solutions: such plane waves give rise to contorsional autointeractions for
which the Ricci metric curvature vanishes and therefore the energy density is
equal to zero identically. Consequences are discussed.Comment: 7 page
Special relativity with two invariant scales: Motivation, Fermions, Bosons, Locality, and Critique
We present a Master equation for description of fermions and bosons for
special relativities with two invariant scales, SR2, (c and lambda_P). We
introduce canonically-conjugate variables (chi^0, chi) to (epsilon, pi) of
Judes-Visser. Together, they bring in a formal element of linearity and
locality in an otherwise non-linear and non-local theory. Special relativities
with two invariant scales provide all corrections, say, to the standard model
of the high energy physics, in terms of one fundamental constant, lambda_P. It
is emphasized that spacetime of special relativities with two invariant scales
carries an intrinsic quantum-gravitational character. In an addenda, we also
comment on the physical importance of a phase factor that the whole literature
on the subject has missed and present a brief critique of SR2. In addition, we
remark that the most natural and physically viable SR2 shall require
momentum-space and spacetime to be non-commutative with the non-commutativity
determined by the spin content and C, P, and T properties of the examined
representation space. Therefore, in a physically successful SR2, the notion of
spacetime is expected to be deeply intertwined with specific properties of the
test particle.Comment: Int. J. Mod. Phys. D (in press). Extended version of a set of two
informal lectures given in "La Sapienza" (Rome, May 2001
Some Remarks on the Neutrino Oscillation Phase in a Gravitational Field
The weak gravitational field expansion method to account for the
gravitationally induced neutrino oscillation effect is critically examined. It
is shown that the splitting of the neutrino phase into a ``kinematic'' and a
``gravitational'' phase is not always possible because the relativistic factor
modifies the particle interference phase splitting condition in a gravitational
field.Comment: 4 pages, no figure
Mass dependence of the gravitationally-induced wave-function phase
The leading mass dependence of the wave function phase is calculated in the
presence of gravitational interactions. The conditions under which this phase
contains terms depending on both the square of the mass and the gravitational
constant are determined. The observability of such terms is briefly discussed.Comment: 5 pages, no figures, requires Revtex. The discussion has been
extended and clarifie
The quadratic spinor Lagrangian, axial torsion current, and generalizations
We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst
actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the
three classes of Dirac spinor fields, under Lounesto spinor field
classification, are considered. To each one of these classes, there corresponds
a unique kind of action for a covariant gravity theory. In other words, it is
shown to exist a one-to-one correspondence between the three classes of
non-equivalent solutions of the Dirac equation, and Einstein-Hilbert,
Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from
Lounesto spinor field classification, that any other class of spinor field
(Weyl, Majorana, flagpole, or flag-dipole spinor fields) yields a trivial
(zero) QSL, up to a boundary term. To investigate this boundary term we do not
impose any constraint on the Dirac spinor field, and consequently we obtain new
terms in the boundary component of the QSL. In the particular case of a
teleparallel connection, an axial torsion 1-form current density is obtained.
New terms are also obtained in the corresponding Hamiltonian formalism. We then
discuss how these new terms could shed new light on more general
investigations.Comment: 9 pages, RevTeX, to be published in Int.J.Mod.Phys.D (2007
Extra Dirac Equations
This paper has rather a pedagogical meaning. Surprising symmetries in the
Lorentz group representation space are analyzed. The aim is
to draw reader's attention to the possibility of describing the particle world
on the ground of the Dirac "doubles". Several tune points of the variational
principle for this kind of equations are briefly discussed.Comment: REVTeX 3.0, 14p
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