674 research outputs found
Neutron Acceleration in Uniform Electromagnetic Fields
The question as to whether neutron acceleration can occur in uniform
electromagnetic fields is examined. Although such an effect has been predicted
using the canonical equations of motion some doubt has been raised recently as
to whether it is in principle observable for a spin 1/2 particle. To resolve
this issue a gedanken experiment is proposed and analyzed using a wave packet
construction for the neutron beam. By allowing arbitrary orientation for the
neutron spin as well as for the electric and magnetic fields a non vanishing
acceleration of the center of the neutron wave packet is found which confirms
the predictions of the canonical formalism.Comment: 11 page
Gravitational Phase Operator and Cosmic Strings
A quantum equivalence principle is formulated by means of a gravitational
phase operator which is an element of the Poincare group. This is applied to
the spinning cosmic string which suggests that it may (but not necessarily)
contain gravitational torsion. A new exact solution of the Einstein-
Cartan-Sciama-Kibble equations for the gravitational field with torsion is
obtained everywhere for a cosmic string with uniform energy density, spin
density and flux. A novel effect due to the quantized gravitational field of
the cosmic string on the wave function of a particle outside the string is used
to argue that spacetime points are not meaningful in quantum gravity.Comment: 22 pages, to be published Phys. Rev. D. Some minor changes have been
made and a reference has been added to the paper of D.V. Gal'tsov and P.S.
Letelier, Phys. Rev. D 47 (1993) 4273, which first contained the metric (2.2)
external to the cosmic string. The present paper extends this solution to a
regular solution inside the string as wel
Classical and Quantum Interaction of the Dipole
A unified and fully relativistic treatment of the interaction of the electric
and magnetic dipole moments of a particle with the electromagnetic field is
given. New forces on the particle due to the combined effect of electric and
magnetic dipoles are obtained. Four new experiments are proposed, three of
which would observe topological phase shifts.Comment: 10 pages, Latex/Revtex. Some minor errors have been correcte
Axiomatic Holonomy Maps and Generalized Yang-Mills Moduli Space
This article is a follow-up of ``Holonomy and Path Structures in General
Relativity and Yang-Mills Theory" by Barrett, J. W. (Int.J.Theor.Phys., vol.30,
No.9, 1991). Its main goal is to provide an alternative proof of this part of
the reconstruction theorem which concerns the existence of a connection. A
construction of connection 1-form is presented. The formula expressing the
local coefficients of connection in terms of the holonomy map is obtained as an
immediate consequence of that construction. Thus the derived formula coincides
with that used in "On Loop Space Formulation of Gauge Theories" by Chan, H.-M.,
Scharbach, P. and Tsou S.T. (Ann.Phys., vol.167, 454-472, 1986). The
reconstruction and representation theorems form a generalization of the fact
that the pointed configuration space of the classical Yang-Mills theory is
equivalent to the set of all holonomy maps. The point of this generalization is
that there is a one-to-one correspondence not only between the holonomy maps
and the orbits in the space of connections, but also between all maps from the
loop space on to group fulfilling some axioms and all possible
equivalence classes of bundles with connection, where the equivalence
relation is defined by bundle isomorphism in a natural way.Comment: amslatex, 7 pages, no figure
Gravity and Geometric Phases
The behavior of a quantum test particle satisfying the Klein-Gordon equation
in a certain class of 4 dimensional stationary space-times is examined. In a
space-time of a spinning cosmic string, the wave function of a particle in a
box is shown to acquire a geometric phase when the box is transported around a
closed path surrounding the string. When interpreted as an Aharonov-Anandan
geometric phase, the effect is shown to be related to the Aharonov-Bohm effect.Comment: 11 pages, latex fil
Testing Bell's inequality using Aharonov-Casher effect
We propose the Aharonov-Casher (AC) effect for four entangled spin-half
particles carrying magnetic moments in the presence of impenetrable line
charge. The four particle state undergoes AC phase shift in two causually
disconnected region which can show up in the correlations between different
spin states of distant particles. This correlation can violate Bell's
inequality, thus displaying the non-locality for four particle entangled states
in an objective way. Also, we have suggested how to control the AC phase shift
locally at two distant locations to test Bell's inequality. We belive that
although the single particle AC effect may not be non-local but the entangled
state AC effect is a non-local one.Comment: Latex, 6 pages, no figures, submitted to Phys. Rev.
Topology, Locality, and Aharonov-Bohm Effect with Neutrons
Recent neutron interferometry experiments have been interpreted as
demonstrating a new topological phenomenon similar in principle to the usual
Aharonov-Bohm (AB) effect, but with the neutron's magnetic moment replacing the
electron's charge. We show that the new phenomenon, called Scalar AB (SAB)
effect, follows from an ordinary local interaction, contrary to the usual AB
effect, and we argue that the SAB effect is not a topological effect by any
useful definition. We find that SAB actually measures an apparently novel spin
autocorrelation whose operator equations of motion contain the local torque in
the magnetic field. We note that the same remarks apply to the Aharonov-Casher
effect.Comment: 9 page
Berry phase in a non-isolated system
We investigate the effect of the environment on a Berry phase measurement
involving a spin-half. We model the spin+environment using a biased spin-boson
Hamiltonian with a time-dependent magnetic field. We find that, contrary to
naive expectations, the Berry phase acquired by the spin can be observed, but
only on timescales which are neither too short nor very long. However this
Berry phase is not the same as for the isolated spin-half. It does not have a
simple geometric interpretation in terms of the adiabatic evolution of either
bare spin-states or the dressed spin-resonances that remain once we have traced
out the environment. This result is crucial for proposed Berry phase
measurements in superconducting nanocircuits as dissipation there is known to
be significant.Comment: 4 pages (revTeX4) 2 fig. This version has MAJOR changes to equation
The non-Abelian state-dependent gauge field in optics
The covariant formulation of the quantum dynamics in CP(1) should lead to the
observable geometrodynamical effects for the local dynamical variable of the
light polarization states.Comment: 8 pages, 3 figures, LaTe
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