5,915 research outputs found
Impacts of the observed theta_{13} on the running behaviors of Dirac and Majorana neutrino mixing angles and CP-violating phases
The recent observation of the smallest neutrino mixing angle in
the Daya Bay and RENO experiments motivates us to examine whether at the electroweak scale can be generated from at a superhigh-energy scale via the radiative corrections. We find
that it is difficult but not impossible in the minimal supersymmetric standard
model (MSSM), and a relatively large may have some nontrivial
impacts on the running behaviors of the other two mixing angles and
CP-violating phases. In particular, we demonstrate that the CP-violating phases
play a crucial role in the evolution of the mixing angles by using the one-loop
renormalization-group equations of the Dirac or Majorana neutrinos in the MSSM.
We also take the "correlative" neutrino mixing pattern with , and at a
presumable flavor symmetry scale as an example to illustrate that the three
mixing angles can receive comparably small radiative corrections and thus
evolve to their best-fit values at the electroweak scale if the CP-violating
phases are properly adjusted.Comment: RevTeX 16 pages, 3 figures, 4 tables, more discussions added,
references updated. Accepted for publication in Phys. Rev.
Possible Deviation from the Tri-bimaximal Neutrino Mixing in a Seesaw Model
We propose a simple but suggestive seesaw model with two phenomenological
conjectures: three heavy (right-handed) Majorana neutrinos are degenerate in
mass in the symmetry limit and three light Majorana neutrinos have the
tri-bimaximal mixing pattern . We show that a small mass splitting
between the first generation and the other two generations of heavy Majorana
neutrinos is responsible for the deviation of the solar neutrino mixing angle
from its initial value given by , and the
slight breaking of the mass degeneracy between the second and third generations
of heavy Majorana neutrinos results in a small mixing angle
and a tiny departure of the atmospheric neutrino mixing angle
from . It turns out that a normal hierarchy of the light neutrino
mass spectrum is favored in this seesaw scenario.Comment: RevTex 12 pages (2 EPS figures included). More discussions and
references adde
The Multiphase Intracluster Medium in Galaxy Groups Probed by the Lyman Alpha Forest
The case is made that the intracluster medium (ICM) in spiral-rich galaxy
groups today probably has undergone much slower evolution than that in
elliptical-rich groups and clusters. The environments of proto-clusters and
proto-groups at z > 2 are likely similar to spiral-rich group environments at
lower redshift. Therefore, like the ICM in spiral-rich groups today, the ICM in
proto-groups and proto-clusters at z > 2 is predicted to be significantly
multiphased. The QSO Lyman alpha forest in the vicinity of galaxies is an
effective probe of the ICM at a wide range of redshift. Two recent observations
of Lyman alpha absorption around galaxies by Adelberger et al. and by
Pascarelle et al are reconciled, and it is shown that observations support the
multiphase ICM scenario. Galaxy redshifts must be very accurate for such
studies to succeed. This scenario can also explain the lower metallicity and
lower hot gas fraction in groups.Comment: 4 pages, 1 figure, replaced with the version after proo
Updated Values of Running Quark and Lepton Masses
Reliable values of quark and lepton masses are important for model building
at a fundamental energy scale, such as the Fermi scale M_Z \approx 91.2 GeV and
the would-be GUT scale \Lambda_GUT \sim 2 \times 10^16 GeV. Using the latest
data given by the Particle Data Group, we update the running quark and
charged-lepton masses at a number of interesting energy scales below and above
M_Z. In particular, we take into account the possible new physics scale (\mu
\sim 1 TeV) to be explored by the LHC and the typical seesaw scales (\mu \sim
10^9 GeV and \mu \sim 10^12 GeV) which might be relevant to the generation of
neutrino masses. For illustration, the running masses of three light Majorana
neutrinos are also calculated. Our up-to-date table of running fermion masses
are expected to be very useful for the study of flavor dynamics at various
energy scales.Comment: 23 pages, 6 tables, 2 figures; version published in PR
Massive and Massless Neutrinos on Unbalanced Seesaws
The observation of neutrino oscillations requires new physics beyond the
standard model (SM). A SM-like gauge theory with p lepton families can be
extended by introducing q heavy right-handed Majorana neutrinos but preserving
its SU(2)_L x U(1)_Y gauge symmetry. The overall neutrino mass matrix M turns
out to be a symmetric (p+q) x (p+q) matrix. Given p>q, the rank of M is in
general equal to 2q, corresponding to 2q non-zero mass eigenvalues. The
existence of (p-q) massless left-handed Majorana neutrinos is an exact
consequence of the model, independent of the usual approximation made in
deriving the Type-I seesaw relation between the effective p x p light Majorana
neutrino mass matrix M_\nu and the q x q heavy Majorana neutrino mass matrix
M_R. In other words, the numbers of massive left- and right-handed neutrinos
are fairly matched. A good example to illustrate this seesaw fair play rule is
the minimal seesaw model with p=3 and q=2, in which one massless neutrino sits
on the unbalanced seesaw.Comment: RevTex 8 pages, 1 PS figure. Two crucial references adde
More on volume dependence of spectral weight function
Spectral weight functions are easily obtained from two-point correlation
functions and they might be used to distinguish single-particle from
multi-particle states in a finite-volume lattice calculation, a problem crucial
for many lattice QCD simulations. In previous studies, it is shown that the
spectral weight function for a broad resonance shares the typical volume
dependence of a two-particle scattering state i.e. proportional to in a
large cubic box of size while the narrow resonance case requires further
investigation. In this paper, a generalized formula is found for the spectral
weight function which incorporates both narrow and broad resonance cases.
Within L\"uscher's formalism, it is shown that the volume dependence of the
spectral weight function exhibits a single-particle behavior for a extremely
narrow resonance and a two-particle behavior for a broad resonance. The
corresponding formulas for both and channels are derived. The
potential application of these formulas in the extraction of resonance
parameters are also discussed
Fate of Chemical Activators in the Aqueous Environment: What Should We Do About IT?
The commonly used activators in chemical activation of activated carbon are very toxic and poisonous to the aquatic environment. Finding trade-off solutions without compromising the quality of activated carbon and jeopardizing the environment have become the subject of considerable interest. This paper is aimed to shed some light on the inevitable release of chemical activators to the aqueous environment, and offers some possible solutions to overcome the emergence of secondary pollution
Shear induced grain boundary motion for lamellar phases in the weakly nonlinear regime
We study the effect of an externally imposed oscillatory shear on the motion
of a grain boundary that separates differently oriented domains of the lamellar
phase of a diblock copolymer. A direct numerical solution of the
Swift-Hohenberg equation in shear flow is used for the case of a
transverse/parallel grain boundary in the limits of weak nonlinearity and low
shear frequency. We focus on the region of parameters in which both transverse
and parallel lamellae are linearly stable. Shearing leads to excess free energy
in the transverse region relative to the parallel region, which is in turn
dissipated by net motion of the boundary toward the transverse region. The
observed boundary motion is a combination of rigid advection by the flow and
order parameter diffusion. The latter includes break up and reconnection of
lamellae, as well as a weak Eckhaus instability in the boundary region for
sufficiently large strain amplitude that leads to slow wavenumber readjustment.
The net average velocity is seen to increase with frequency and strain
amplitude, and can be obtained by a multiple scale expansion of the governing
equations
Superconductivity up to 30 K in the vicinity of quantum critical point in BaFe(AsP)
We report bulk superconductivity induced by an isovalent doping of phosphorus
in BaFe(AsP). The P-for-As substitution results in
shrinkage of lattice, especially for the FeAs block layers. The resistivity
anomaly associated with the spin-density-wave (SDW) transition in the undoped
compound is gradually suppressed by the P doping. Superconductivity with the
maximum of 30 K emerges at =0.32, coinciding with a magnetic quantum
critical point (QCP) which is evidenced by the disappearance of SDW order and
the linear temperature-dependent resistivity in the normal state. The
values were found to decrease with further P doping, and no superconductivity
was observed down to 2 K for 0.77. The appearance of superconductivity
in the vicinity of QCP hints to the superconductivity mechanism in iron-based
arsenides.Comment: 9 pages, 4 figures; more data; to appear in Journal of Physics:
Condensed Matte
Evolving small-world networks with geographical attachment preference
We introduce a minimal extended evolving model for small-world networks which
is controlled by a parameter. In this model the network growth is determined by
the attachment of new nodes to already existing nodes that are geographically
close. We analyze several topological properties for our model both
analytically and by numerical simulations. The resulting network shows some
important characteristics of real-life networks such as the small-world effect
and a high clustering.Comment: 11 pages, 4 figure
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