3,121 research outputs found
Neutrinos, Axions and Conformal Symmetry
We demonstrate that radiative breaking of conformal symmetry (and
simultaneously electroweak symmetry) in the Standard Model with right-chiral
neutrinos and a minimally enlarged scalar sector induces spontaneous breaking
of lepton number symmetry, which naturally gives rise to an axion-like particle
with some unusual features. The couplings of this `axion' to Standard Model
particles, in particular photons and gluons, are entirely determined (and
computable) via the conformal anomaly, and their smallness turns out to be
directly related to the smallness of the masses of light neutrinos.Comment: 10 pages, 2 figures, expanded version, to be published in EPJ
The isospin symmetry breaking effects in decays
The Fermi-Watson theorem is generalized to the case of two coupled channels
with different masses and applied to final state interaction in
decays. The impact of considered effect on the phase of the scattering
is estimated and shown that it can be crucial for scattering lengths extraction
from experimental data on decays
Broadband Geodesic Pulses for Three Spin Systems: Time-Optimal Realization of Effective Trilinear Coupling Terms and Indirect SWAP Gates
Broadband implementations of time-optimal geodesic pulse elements are
introduced for the efficient creation of effective trilinear coupling terms for
spin systems consisting of three weakly coupled spins 1/2. Based on these pulse
elements, the time-optimal implementation of indirect SWAP operations is
demonstrated experimentally. The duration of indirect SWAP gates based on
broadband geodesic sequence is reduced by 42.3% compared to conventional
approaches.Comment: 22 pages, incl. 8 figure
Brane localization of gravity in higher derivative theory
We consider a class of higher order corrections in the form of Euler
densities of arbitrary rank to the standard gravity action in
dimensions. We have previously shown that this class of corrections allows for
domain wall solutions despite the presence of higher powers of the curvature.
In the present paper we explicitly solve the linearized equation of motion for
gravity fluctuations around the domain wall background and show that there
always exist one massless state (graviton) propagating on the wall and a
continuous tower of massive states propagating in the bulk.Comment: 14 pages, Late
Comportamento de espécies de citros para o Citrus Tristeza virus (CTV) em diferentes ecossistemas.
A tristeza dos citros, causada pelo Citrus tristeza virus (CTV), levou a dizimação dos pomares brasileiros em décadas passadas. O convívio com esta doença, endêmica no Brasil, só foi possível por meio da utilização de porta-enxertos tolerantes e pela pré-imunização de copas muito suscetíveis. O estabelecimento da citricultura em diferentes ecossistemas na Bahia, associado ao uso de novas variedades, torna necessário estudar o seu comportamento. Isto permitirá a seleção de plantas mais tolerantes para cada local.PDF. 161_11
Author Correction: LKB1 loss links serine metabolism to DNA methylation and tumorigenesis
Erratum for: LKB1 loss links serine metabolism to DNA methylation and tumorigenesis. [Nature. 2016
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
Semiclassical quantisation of space-times with apparent horizons
Coherent or semiclassical states in canonical quantum gravity describe the
classical Schwarzschild space-time. By tracing over the coherent state
wavefunction inside the horizon, a density matrix is derived.
Bekenstein-Hawking entropy is obtained from the density matrix, modulo the
Immirzi parameter. The expectation value of the area and curvature operator is
evaluated in these states. The behaviour near the singularity of the curvature
operator shows that the singularity is resolved. We then generalise the results
to space-times with spherically symmetric apparent horizons.Comment: 52 pages, 4 figure
Chiral unitary approach to S-wave meson baryon scattering in the strangeness S=0 sector
We study the S-wave interaction of mesons with baryons in the strangeness S=0
sector in a coupled channel unitary approach. The basic dynamics is drawn from
the lowest order meson baryon chiral Lagrangians. Small modifications inspired
by models with explicit vector meson exchange in the t-channel are also
considered. In addition the pi pi N channel is included and shown to have an
important repercussion in the results, particularly in the isospin 3/2 sector.Comment: 23 pages, LaTeX, 21 figure
Exploring \pp scattering in the \1N picture
In the large approximation to , the leading \pp scattering
amplitude is expressed as the sum of an infinite number of tree diagrams. We
investigate the possibility that an adequate approximation at energies up to
somewhat more than one can be made by keeping diagrams which involve the
exchange of resonances in this energy range in addition to the simplest chiral
contact terms. In this approach crossing symmetry is automatic but individual
terms tend to drastically violate partial wave unitarity. We first note that
the introduction of the meson in a chirally invariant manner
substantially delays the onset of drastic unitarity violation which would be
present for the {\it current algebra} term alone. This suggests a possibility
of local (in energy) cancellation which we then explore in a phenomenological
way. We include exchanges of leading resonances up to the region.
However, unitarity requires more structure which we model by a four derivative
contact term or by a low lying scalar resonance which is presumably subleading
in the \1N expansion, but may nevertheless be important. The latter two
flavor model gives a reasonable description of the phase shift up
until around , before the effects associated which the
threshold come into play.Comment: 27 LaTex pages + 13 figures (also available in hard-copy
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