27 research outputs found

### Helicity Precession of Spin-1/2 Particles in Weak Inertial and Gravitational Fields

We calculate the helicity and chirality effects experienced by a spin-1/2
particle subjected to classical electromagnetic and gravitational fields. The
helicity evolution is then determined in the non-relativistic, relativistic,
and ultra-relativistic regimes. We find that inertia-gravitation can
distinguish between helicity and chirality. Helicity is not conserved, in
general, even when the particles are massless. In this case, however, the
inertial fields can hardly be applied to the fermions.Comment: 17 pages with no figures. Submitted to Nuclear Physics

### Breakdown of Casimir Invariance in Curved Space-Time

It is shown that the commonly accepted definition for the Casimir scalar
operators of the Poincare group does not satisfy the properties of Casimir
invariance when applied to the non-inertial motion of elementary particles
while in the presence of external gravitational and electromagnetic fields,
where general curvilinear co-ordinates are used to describe the momentum
generators within a Fermi normal co-ordinate framework. Specific expressions of
the Casimir scalar properties are presented for spin-1/2 to spin-2 particles
inclusive. While the Casimir scalar for linear momentum remains a Lorentz
invariant in the absence of external fields, this is no longer true for the
spin Casimir scalar. Potential implications are considered for the propagation
of photons, gravitons, and gravitinos as described by the spin-3/2
Rarita-Schwinger vector-spinor field. In particular, it is shown that
non-inertial motion introduces a frame-based effective mass to the spin
interaction, with interesting physical consequences that are explored in
detail.Comment: 18 pages, 1 figure; accepted for publication in Annalen der Physi

### Reply to Comment on ``Can gravity distinguish between Dirac and Majorana neutrinos?''

This is a reply to a comment (gr-qc/0610098) written by Nieves and Pal about
our paper (gr-qc/0605153) published in Phys. Rev. Lett. 97, 041101 (2006).Comment: 1 page, no figures, REVTe

### A New Perspective on Path Integral Quantum Mechanics in Curved Space-Time

A fundamentally different approach to path integral quantum mechanics in
curved space-time is presented, as compared to the standard approaches
currently available in the literature. Within the context of scalar particle
propagation in a locally curved background, such as described by Fermi or
Riemann normal co-ordinates, this approach requires use of a constructed
operator to rotate the initial, intermediate, and final position ket vectors
onto their respective local tangent spaces, defined at each local time step
along some arbitrary classical reference worldline. Local time translation is
described using a quantum mechanical representation of Lie transport, that
while strictly non-unitary in operator form, nevertheless correctly recovers
the free-particle Lagrangian in curved space-time, along with new
contributions. This propagator yields the prediction that all probability
violating terms due to curvature contribute to a quantum violation of the weak
equivalence principle, while the remaining terms that conserve probability also
correspondingly satisfy the weak equivalence principle, at least to
leading-order in the particle's Compton wavelength. Furthermore, this
propagator possesses an overall curvature-dependent and gauge-invariant phase
factor that can be interpreted as the gravitational Aharonov-Bohm effect and
Berry's phase.Comment: 14 pages, 1 figure; major additions and revisions introduced; main
conclusions are unchanged; new affiliation adde

### Radiative and non radiative muon capture on the proton in heavy baryon chiral perturbation theory

We have evaluated the amplitude for muon capture by a proton, mu + p --> n +
nu, to O(p^3) within the context of heavy baryon chiral perturbation theory
(HBChPT) using the new O(p^3) Lagrangian of Ecker and Mojzis (E&M). We obtain
expressions for the standard muon capture form factors and determine three of
the coefficients of the E&M Lagrangian, namely, b_7, b_{19}, and b_{23}. We
describe progress on the next step, a calculation of the radiative muon capture
process, mu + p --> n + nu + gamma.Comment: Talk at the 15th Int. Conf. on Few-Body Problems in Physics, 22-26
July, 1997, Groningen, The Netherlands, to be published in the proceedings; 5
pages, LaTeX, using espcrc1.st

### Can Gravity Distinguish Between Dirac and Majorana Neutrinos?

We show that spin-gravity interaction can distinguish between Dirac and
Majorana neutrino wave packets propagating in a Lense-Thirring background.
Using time-independent perturbation theory and gravitational phase to generate
a perturbation Hamiltonian with spin-gravity coupling, we show that the
associated matrix element for the Majorana neutrino differs significantly from
its Dirac counterpart. This difference can be demonstrated through significant
gravitational corrections to the neutrino oscillation length for a two-flavour
system, as shown explicitly for SN1987A.Comment: 4 pages, 2 figures; minor changes of text; typo corrected; accepted
in Physical Review Letter

### The implications of noninertial motion on covariant quantum spin

It is shown that the Pauli-Lubanski spin vector defined in terms of
curvilinear co-ordinates does not satisfy Lorentz invariance for spin-1/2
particles in noninertial motion along a curved trajectory. The possibility of
detecting this violation in muon decay experiments is explored, where the
noninertial contribution to the decay rate becomes large for muon beams with
large momenta and trajectories with radius of curvature approaching the muon's
Compton wavelength scale. A new spacelike spin vector is derived from the
Pauli-Lubanski vector that satisfies Lorentz invariance for both inertial and
noninertial motion. In addition, this spin vector suggests a generalization for
the classification of spin-1/2 particles, and has interesting properties that
are applicable for both massive and massless particles.Comment: REVTeX file; 7 pages; 2 figures; slightly revised with new abstract;
accepted for publication in Classical and Quantum Gravit