17 research outputs found
Dirac Particles in a Gravitational Field
The semiclassical approximation for the Hamiltonian of Dirac particles
interacting with an arbitrary gravitational field is investigated. The time
dependence of the metrics leads to new contributions to the in-band energy
operator in comparison to previous works on the static case. In particular we
find a new coupling term between the linear momentum and the spin, as well as
couplings which contribute to the breaking of the particle - antiparticle
symmetry
Diagonal Representation for a Generic Matrix Valued Quantum Hamiltonian
A general method to derive the diagonal representation for a generic matrix
valued quantum Hamiltonian is proposed. In this approach new mathematical
objects like non-commuting operators evolving with the Planck constant promoted
as a running variable are introduced. This method leads to a formal compact
expression for the diagonal Hamiltonian which can be expanded in a power series
of the Planck constant. In particular, we provide an explicit expression for
the diagonal representation of a generic Hamiltonian to the second order in the
Planck constant. This last result is applied, as a physical illustration, to
Dirac electrons and neutrinos in external fields.Comment: Significant revision, typos corrected and references adde
A Gravitational Potential with Extra-dimensions and Spin Effects In Hadronic Reactions
The impact of the KK-modes in d-brane models of gravity with large
compactification radii and TeV-scale quantum gravity on the hadronic potential
at small impact parameters is examined. The effects of the gravitational
hadronic form factors obtained from the generalized parton distributions (GPDs)
on the behavior of the gravitational potential and the possible spin
correlation effects are also analysed.Comment: 13 pages, 7 figure
Quantum Theory in Accelerated Frames of Reference
The observational basis of quantum theory in accelerated systems is studied.
The extension of Lorentz invariance to accelerated systems via the hypothesis
of locality is discussed and the limitations of this hypothesis are pointed
out. The nonlocal theory of accelerated observers is briefly described.
Moreover, the main observational aspects of Dirac's equation in noninertial
frames of reference are presented. The Galilean invariance of nonrelativistic
quantum mechanics and the mass superselection rule are examined in the light of
the invariance of physical laws under inhomogeneous Lorentz transformations.Comment: 25 pages, no figures, contribution to Springer Lecture Notes in
Physics (Proc. SR 2005, Potsdam, Germany, February 13 - 18, 2005
Spin-gravity coupling and gravity-induced quantum phases
External gravitational fields induce phase factors in the wave functions of
particles. The phases are exact to first order in the background gravitational
field, are manifestly covariant and gauge invariant and provide a useful tool
for the study of spin-gravity coupling and of the optics of particles in
gravitational or inertial fields. We discuss the role that spin-gravity
coupling plays in particular problems.Comment: 18 pages, 1 figur