7 research outputs found
Charged fermion in -dimensional wormhole with axial magnetic field
We investigate the effects of magnetic field on a charged fermion in a
-dimensional wormhole. Applying external magnetic field along the axis
direction of the wormhole, the Dirac equation is set up and analytically solved
in two scenarios, constant magnetic flux and constant magnetic field through
the throat of the wormhole. For the constant magnetic flux scenario, the system
can be solved analytically and exact solutions are found. For the constant
magnetic field scenario, with the short wormhole approximation, the quantized
energies and eigenstates are obtained. The system exhibits both the spin-orbit
coupling and the Landau quantization for the stationary states in both
scenarios. The intrinsic curvature of the surface induces the spin-orbit and
spin-magnetic Landau couplings that generate imaginary energy. Imaginary energy
can be interpreted as the energy dissipation and instability of the states.
Generically, the states of charged fermion in wormhole are quasinormal
modes~(QNMs) that could be unstable for positive imaginary frequencies and
decaying for negative imaginary ones. For the constant flux scenario, the
fermions in the wormhole can behave like bosons and have arbitrary statistics
depending on the flux. We also discuss the implications of our results in the
graphene wormhole system.Comment: 24 pages, 2 figures, revised version submitted to journal on June 17,
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Scattering of charged fermion to two-dimensional wormhole with constant axial magnetic flux
Scattering of charged fermion with -dimensional wormhole in the
presence of constant axial magnetic flux is explored. By extending the class of
fermionic solutions of the Dirac equation in the curved space of wormhole
surface to include normal modes with real energy and momentum, we found a
quantum selection rule for the scattering of fermion waves to the wormhole. The
newly found {\it momentum-angular momentum relation} implies that only fermion
with the quantized momentum can be transmitted through the
hole. The allowed momentum is proportional to an effective angular momentum
quantum number and inversely proportional to the radius of the throat of
the wormhole . Flux dependence of the effective angular momentum quantum
number permits us to select fermions that can pass through according to their
momenta. A conservation law is also naturally enforced in terms of the
unitarity condition among the incident, reflected, and transmitted waves. The
scattering involving quasinormal modes~(QNMs) of fermionic states in the
wormhole is subsequently explored. It is found that the transmitted waves
through the wormhole for all scenarios involving QNMs are mostly suppressed and
decaying in time. In the case of QNMs scattering, the unitarity condition is
violated but a more generic relation of the scattering coefficients is
established. When the magnetic flux , i.e., quantized in units of
the magnetic flux quantum , the fermion will tunnel through the wormhole
with zero reflection.Comment: 18 pages, 7 figure
Dark matter as a Weyl geometric effect
We investigate the possibility that the observed behavior of test particles
outside galaxies, which is usually explained by assuming the existence of dark
matter, is the result of the dynamical evolution of particles in a Weyl type
geometry, and its associated conformally invariant Weyl geometric quadratic
gravity. As a first step in our investigations we write down the simplest
possible conformally invariant gravitational action, constructed in Weyl
geometry, and containing the Weyl scalar, and the strength of the Weyl vector
only. By introducing an auxiliary scalar field, the theoretical model can be
reformulated in the Riemann geometry as scalar-vector-tensor theory, containing
a scalar field, and the Weyl vector, respectively. The field equations of the
theory are derived in the metric formalism, in the absence of matter. A
specific static, spherically symmetric model, in which the Weyl vector has only
a radial component, is considered. In this case, an exact analytic solution of
the gravitational field equations can be obtained. The behavior of the galactic
rotation curves is also considered in detail, and it is shown that an effective
geometric mass term, with an associated density profile, can also be
introduced. Three particular cases, corresponding to some specific functional
forms of the Weyl vector, are also investigated. A comparison of the model with
a selected sample of galactic rotation curves is also performed when an
explicit breaking of conformal invariance is introduced, which allows the fix
of the numerical values of the free parameters of the model. Our results show
that Weyl geometric models can be considered as a viable theoretical
alternative to the dark matter paradigm.Comment: 20 pages, 2 figures, accepted for publication in PR
Electromagnetic Wave Theory and Applications
Contains table of contents for Section 3, reports on nine research projects and a list of publications.National Aeronautics and Space Administration Contract 958461U.S. Navy - Office of Naval Research Grant N00014-92-J-1616University of California/Jet Propulsion Laboratory Contract 960408U.S. Army - Corps of Engineers/Cold Regions Research and Engineering Laboratory Contract DACA89-95-K-0014Mitsubishi CorporationU.S. Navy - Office of Naval Research Agreement N00014-92-J-4098Federal Aviation AdministrationDEMACOJoint Services Electronics Program Grant DAAHO4-95-1-003
Electromagnetic Wave Theory and Applications
Contains table of content for Section 3, reports on ten research projects and a list of publications.U.S. Navy - Office of Naval Research Contract N00014-92-J-4098U.S. Federal Aviation Administration Contract 94-G-007U.S. Federal Aviation Administration Contract 97-G-031California Institute of Technology Contract JPL 960408National Aeronautics and Space Administration Contract JPL 958461U.S. Navy - Office of Naval Research Contract N00014-92-J-1616National Science Foundation Grant ECS 96-15799U.S. Navy - Office of Naval Research Contract N00014-97-1-0172Joint Services Electronics Program Contract DAAH04-95-1-0038Mitsubishi Corporatio
Electromagnetic scattering model for saline ice covered with frost flowers
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 83-87).by Kulapant Pimsamarn.M.Eng