3,796 research outputs found
A relation between CP violation of low energy and leptogenesis
We discuss how CP violation generating lepton number asymmetry can be related
to CP violation in low energy.Comment: A poster Talk presented at KEKTC5, submitted to the proceeding
Exact Parametrization of Majorana Neutrino Mass Matrix with Large Mixing
Under the assumption that the neutrinos are Majorana particles we study how
the lepton mass matrices can be transformed into the simple form which has the
same physical quantities by removing redundant parameters. We propose the exact
parametrization of the lepton mass matrices which reflects the small nu_e-nu_mu
mixing and the large nu_mu-nu_tau mixing. The relations between the twelve
parameters and the physical quantities are shown. Furthermore we calculate the
MNS matrix by applying the assumptions used in the quark sector. Finally we
also check the validity of these assumptions from the experimental values.Comment: 11 pages, LaTeX, no figure
Numerical study on the correlation between CP violation in neutrino oscillations and baryogenesis
We numerically study the correlation between CP violation in the neutrino
oscillations and baryogenesis in the seesaw model. In this study we get the
heavy Majorana neutrino masses and lepton number asymmetries from their decays
by fitting the data of neutrino oscillations and by working on some hypothesis
of the Dirac-Yukawa term for neutrinos.Comment: 3 pages, 2 figures, Latex, presented at KEKTC5(Nov. 2001), to be
published in Nucl. Phys. Proc. Supp
The evolution of genetics to genomics
Development of civilizations and the technology of Development improvement of crop and animals have been under human control for more than 10.000 years. Despite the term Genetics started being employed a few centuries ago, its practice is ancient and responsible for thriving of the human society to the point we see now. The recent advances in this fi eld started with the theories of evolution, mathematical models to predict traits, and studies at cellular level. The explosion of knowledge on the last few decades associated with the advancing of internet and computers led to advent of a new discipline in genetics: genomics. Here is discussed the transition from genetics to genomics and some of the main factors that were responsible for this progress. Nowadays genomics is part of most of life science studies and the outcomes are leading to outstanding discoveries on how the genome is precisely concerted; the fi ndings have been crucial to understand human illness and for development of personalized and more precise medical treatment.Development of civilizations and the technology of Development improvement of crop and animals have been under human control for more than 10.000 years. Despite the term Genetics started being employed a few centuries ago, its practice is ancient and responsible for thriving of the human society to the point we see now. The recent advances in this fi eld started with the theories of evolution, mathematical models to predict traits, and studies at cellular level. The explosion of knowledge on the last few decades associated with the advancing of internet and computers led to advent of a new discipline in genetics: genomics. Here is discussed the transition from genetics to genomics and some of the main factors that were responsible for this progress. Nowadays genomics is part of most of life science studies and the outcomes are leading to outstanding discoveries on how the genome is precisely concerted; the fi ndings have been crucial to understand human illness and for development of personalized and more precise medical treatment
Leptogenesis and Low energy CP violation, a link
How is CP violation of low energy related to CP violation required from
baryon number asymmetry ? We give an example which shows a direct link between
CP violation of neutrino oscillation and baryogenesis through leptogenesis.Comment: 3 pages and 2 figures, Talk presented at 4th Nufac02, July 1-6, 200
Differential Geometry Methods for Constructing Manifold-Targeted Recurrent Neural Networks
Neural computations can be framed as dynamical processes, whereby the structure of the dynamics within a neural network is a direct reflection of the computations that the network performs. A key step in generating mechanistic interpretations within this computation through dynamics framework is to establish the link among network connectivity, dynamics, and computation. This link is only partly understood. Recent work has focused on producing algorithms for engineering artificial recurrent neural networks (RNN) with dynamics targeted to a specific goal manifold. Some of these algorithms require only a set of vectors tangent to the target manifold to be computed and thus provide a general method that can be applied to a diverse set of problems. Nevertheless, computing such vectors for an arbitrary manifold in a high-dimensional state space remains highly challenging, which in practice limits the applicability of this approach. Here we demonstrate how topology and differential geometry can be leveraged to simplify this task by first computing tangent vectors on a low-dimensional topological manifold and then embedding these in state space. The simplicity of this procedure greatly facilitates the creation of manifold-targeted RNNs, as well as the process of designing task-solving, on-manifold dynamics. This new method should enable the application of network engineering–based approaches to a wide set of problems in neuroscience and machine learning. Our description of how fundamental concepts from differential geometry can be mapped onto different aspects of neural dynamics is a further demonstration of how the language of differential geometry can enrich the conceptual framework for describing neural dynamics and computation
Protocol to Study Spatial Subgoal Learning Using Escape Behavior in Mice
Rodent spatial navigation is a key model system for studying mammalian cognition and its neural mechanisms. Of particular interest is how animals memorize the structure of their environments and compute multi-step routes to a goal. Previous work on multi-step spatial reasoning has generally involved placing rodents at the start of a maze until they learn to navigate to a reward without making wrong turns. It thus remains poorly understood how animals rapidly learn about the structure of naturalistic open environments with goals and obstacles. Here we present an assay in which mice spontaneously memorize two-step routes in an environment with a shelter and an obstacle. We allow the mice to explore this environment for 20 min, and then we remove the obstacle. We then present auditory threat stimuli, causing the mouse to escape to the shelter. Finally, we record each escape route and measure whether it targets the shelter directly (a 'homing-vector' escape) or instead targets the location where the obstacle edge was formerly located (an 'edge-vector' escape). Since the obstacle is no longer there, these obstacle-edge-directed escape routes provide evidence that the mouse has memorized a subgoal location, i.e., a waypoint targeted in order to efficiently get to the shelter in the presence of an obstacle. By taking advantage of instinctive escape responses, this assay probes a multi-step spatial memory that is learned in a single session without pretraining. The subgoal learning phenomenon it generates can be useful not only for researchers working on navigation and instinctive behavior, but also for neuroscientists studying the neural basis of multi-step spatial reasoning
Small violations of unitarity, the phase in Bs mixing and visible t->cZ decays at the LHC
We show that it is possible to accommodate the observed size of the phase in
--, mixing in the framework of a model with violation of
unitarity. This violation is associated to the presence of a new
isosinglet quark , which mixes both with and and has a mass
not exceeding 500 GeV. The crucial point is the fact that this framework allows
for of order , to be
contrasted with the situation in the Standard Model, where is
constrained to be of order . We point out that this scenario implies
rare top decays at a rate observable at the LHC and
significantly different from unity. In this framework, one may also account for
the observed size of -- mixing without having to invoke long
distance contributions. It is also shown that in the present scenario, the
observed size of -- mixing constrains
to be of order
, which is significantly smaller than what is allowed in generic
models with violations of unitarity.Comment: 20 pages. References added. Additional observables considered,
updated numerical examples, conclusions unchange
Jarlskog-like invariants for theories with scalars and fermions
Within the framework of theories where both scalars and fermions are present,
we develop a systematic prescription for the construction of CP-violating
quantities that are invariant under basis transformations of those matter
fields. In theories with Spontaneous Symmetry Breaking, the analysis involves
the vevs' transformation properties under a scalar basis change, with a
considerable simplification of the study of CP violation in the scalar sector.
These techniques are then applied in detail to the two Higgs-doublet model with
quarks. It is shown that there are new invariants involving scalar-fermion
interactions, besides those already derived in previous analyses for the
fermion-gauge and scalar-gauge sectors.Comment: 12 pages, Latex, no figure
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