15,276 research outputs found
Non-Hermitian shortcut to stimulated Raman adiabatic passage
We propose a non-Hermitian generalization of stimulated Raman adiabatic
passage (STIRAP), which allows one to increase speed and fidelity of the
adiabatic passage. This is done by adding balanced imaginary (gain/loss) terms
in the diagonal (bare energy) terms of the Hamiltonian and choosing them such
that they cancel exactly the nonadiabatic couplings, providing in this way an
effective shortcut to adiabaticity. Remarkably, for a STIRAP using delayed
Gaussian-shaped pulses in the counter-intuitive scheme the imaginary terms of
the Hamiltonian turn out to be time independent. A possible physical
realization of non-Hermitian STIRAP, based on light transfer in three
evanescently-coupled optical waveguides, is proposed.Comment: 7 pages, 4 figure
How sensitive is a neutrino factory to the angle ?
We consider the impact of non-standard interactions of neutrinos (NSI) on the
determination of neutrino mixing parameters at a neutrino factory using
\pnu{e}\to\pnu{\mu} ``golden channels'' for the measurement of .
We show how a small residual NSI leads to a drastic loss in sensitivity in
, of up to two orders of magnitude. This can be somewhat overcome
if two baselines are combined.Comment: 4 pages, 3 figure
Quantum simulation of the Riemann-Hurwitz zeta function
We propose a simple realization of a quantum simulator of the Riemann-Hurwitz
(RH) \zeta\ function based on a truncation of its Dirichlet representation. We
synthesize a nearest-neighbour-interaction Hamiltonian, satisfying the property
that the temporal evolution of the autocorrelation function of an initial bare
state of the Hamiltonian reproduces the RH function along the line \sigma+i
\omega t of the complex plane, with \sigma>1. The tight-binding Hamiltonian
with engineered hopping rates and site energies can be implemented in a variety
of physical systems, including trapped ion systems and optical waveguide
arrays. The proposed method is scalable, which means that the simulation can be
in principle arbitrarily accurate. Practical limitations of the suggested
scheme, arising from a finite number of lattice sites N and from decoherence,
are briefly discussed.Comment: 6 pages, 3 figure
Chern-Simons anomaly as polarization effect
The parity violating Chern-Simons term in the epoch before the electroweak
phase transition can be interpreted as a polarization effect associated to
massless right-handed electrons (positrons) in the presence of a large-scale
seed hypermagnetic field. We reconfirm the viability of a unified seed field
scenario relating the cosmological baryon asymmetry and the origin of the
protogalactic large-scale magnetic fields observed in astronomy.Comment: 4 pages, latex, matches published versio
Inverse tri-bimaximal type-III seesaw and lepton flavor violation
We present a type-III version of inverse seesaw or, equivalently an inverse
version of type-III seesaw. Naturally small neutrino masses arise at low-scale
from the exchange of neutral fermions transforming as hyperchargeless SU(2)
triplets. In order to implement tri-bimaximal lepton mixing we supplement the
minimal SU(3)xSU(2)xU(1) gauge symmetry with an A4-based flavor symmetry. Our
scenario induces lepton flavour violating (LFV) three body decays that can
proceed at the tree level, while radiative li to lj gamma decays and mu-e
conversion in nuclei are also expected to be sizeable. LFV decays are related
by the underlying flavor symmetry and the new fermions are also expected to be
accessible for study at the Large Hadron Collider (LHC)
Radiative zone solar magnetic fields and g-modes
We consider a generalized model of seismic-wave propagation that takes into
account the effect of a central magnetic field in the Sun. We determine the
g-mode spectrum in the perturbative magnetic field limit using a
one-dimensional Magneto-Hydrodynamics (MHD) picture. We show that central
magnetic fields of about 600-800 kG can displace the pure g-mode frequencies by
about 1%, as hinted by the helioseismic interpretation of GOLF observations.Comment: 6 pages, 4 figures; final version to appear in MNRA
Novel Supersymmetric SO(10) Seesaw Mechanism
We propose a new seesaw mechanism for neutrino masses within a class of
supersymmetric SO(10) models with broken D-parity. It is shown that in such
scenarios the B-L scale can be as low as TeV without generating inconsistencies
with gauge coupling unification nor with the required magnitude of the light
neutrino masses. This leads to a possibly light new neutral gauge boson as well
as relatively light quasi-Dirac heavy leptons. These particles could be at the
TeV scale and mediate lepton flavour and CP violating processes at appreciable
levels.Comment: 4 pages, 3 figures, revtex4, references added, typos corrected,
sharper discussion of the RGEs give
Status of three-neutrino oscillations after the SNO-salt data
We perform a global analysis of neutrino oscillation data in the framework of
three neutrinos, including the recent improved measurement of the neutral
current events at SNO. In addition to all current solar neutrino data we take
into account the reactor neutrino data from KamLAND and CHOOZ, the atmospheric
neutrino data from Super-Kamiokande and MACRO, as well as the first spectral
data from the K2K long baseline accelerator experiment. The up-to-date best fit
values and allowed ranges of the three-flavour oscillation parameters are
determined from these data. Furthermore, we discuss in detail the status of the
small parameters alpha = Delta_m^2_Sol / Delta_m^2_Atm and sin^2(theta_13),
which fix the possible strength of CP violating effects in neutrino
oscillations.Comment: 16 pages, LaTeX file using RevTEX4, 10 figures and 1 table included.
The conclusions reached in version 1 regarding the restriction on
sin^2(theta_13) are now corrected, the solar bound is weaker than that from
reactors even after the inclusion of the SNO salt data. In addition the full
data set has now been reanalized using the pull method instead of the
standard chi-square approach. A few references have also been adde
- …