3,497 research outputs found
Quasiclassical Coarse Graining and Thermodynamic Entropy
Our everyday descriptions of the universe are highly coarse-grained,
following only a tiny fraction of the variables necessary for a perfectly
fine-grained description. Coarse graining in classical physics is made natural
by our limited powers of observation and computation. But in the modern quantum
mechanics of closed systems, some measure of coarse graining is inescapable
because there are no non-trivial, probabilistic, fine-grained descriptions.
This essay explores the consequences of that fact. Quantum theory allows for
various coarse-grained descriptions some of which are mutually incompatible.
For most purposes, however, we are interested in the small subset of
``quasiclassical descriptions'' defined by ranges of values of averages over
small volumes of densities of conserved quantities such as energy and momentum
and approximately conserved quantities such as baryon number. The
near-conservation of these quasiclassical quantities results in approximate
decoherence, predictability, and local equilibrium, leading to closed sets of
equations of motion. In any description, information is sacrificed through the
coarse graining that yields decoherence and gives rise to probabilities for
histories. In quasiclassical descriptions, further information is sacrificed in
exhibiting the emergent regularities summarized by classical equations of
motion. An appropriate entropy measures the loss of information. For a
``quasiclassical realm'' this is connected with the usual thermodynamic entropy
as obtained from statistical mechanics. It was low for the initial state of our
universe and has been increasing since.Comment: 17 pages, 0 figures, revtex4, Dedicated to Rafael Sorkin on his 60th
birthday, minor correction
Quark-lepton symmetry and complementarity
We argue that the difference between the observed approximate quark-lepton
complementarity and the theoretical prediction based on realistic quark-lepton
symmetry within the seesaw mechanism may be adjusted by means of a triplet
contribution in the seesaw formula.Comment: 7 pages, RevTex
The Frobenius group T13 and the canonical see-saw mechanism applied to neutrino mixing
The compatibility of the Frobenius group T13 with the canonical see-saw
mechanism of neutrino mixing is examined. The Standard Model is extended in a
minimalist way, by introducing a family symmetry and three right-handed
neutrinos. To fit experiments and place constraints on the possibilities,
tribimaximal mixing is used as a guideline. The application of both a family
symmetry group and the canonical see-saw mechanism naturally generates small
neutrino masses. The various possibilities from combining these two models are
listed. Enough constraints are produced to narrow down the parameters of the
neutrino mass matrix to two. This is therefore a predictive model where
neutrino mass eigenvalues and allowed regions for neutrinoless double beta
decay are suggested.Comment: Accepted for publication in Physical Review D. 13 page
GeV Majorana Neutrinos in Top-quark Decay at the LHC
We explore the \Delta L=2 same-sign dilepton signal from top-quark decay via
a Majorana neutrino at the LHC in the top anti-top pair production samples. The
signature is same-sign dilepton plus multi-jets with no significant missing
energy. The most optimistic region lies where the Majorana neutrino mass is
between 15-65 GeV. For 300 fb^-1 integrated luminosity, it is possible to probe
S_{ij}, the effective mixing parameter, to order of 10^-5.Comment: 15 pages, 8 figure
Observing Signals of the Bulk Matter RS Model through Rare Decays of SUSY Particles
The bulk matter Randall-Sundrum (RS) model is a setup where Standard Model
(SM) matter and gauge fields reside in the bulk of 5D warped spacetime while
the Higgs field is confined on the IR brane. The wavefunctions of the 1st and
2nd generation matter particles are localized towards the UV brane and those of
the 3rd generation towards the IR brane, so that the hierarchical structure of
the Yukawa couplings arises geometrically without hierarchy in fundamental
parameters. This paper discusses an experimental test of this model in the case
where the Kaluza-Klein scale is far above the collider scale, but the model is
combined with 5D Minimal SUSY Standard Model (MSSM) and SUSY particles are in
the reach of collider experiments. A general SUSY breaking mass spectrum
consistent with the bulk matter RS model is considered: SUSY breaking sector
locates on the IR brane and its effects are mediated to 5D MSSM through a
hybrid of gravity mediation, gaugino mediation and gauge mediation. This paper
argues that it is possible to observe the signals of the bulk matter RS model
through rare decays of "almost SU(2) singlet mass eigenstates" that are induced
by flavor-violating gravity mediation contributions to matter soft SUSY
breaking terms
Quasiclassical Equations of Motion for Nonlinear Brownian Systems
Following the formalism of Gell-Mann and Hartle, phenomenological equations
of motion are derived from the decoherence functional formalism of quantum
mechanics, using a path-integral description. This is done explicitly for the
case of a system interacting with a ``bath'' of harmonic oscillators whose
individual motions are neglected. The results are compared to the equations
derived from the purely classical theory. The case of linear interactions is
treated exactly, and nonlinear interactions are compared using classical and
quantum perturbation theory.Comment: 24 pages, CALT-68-1848 (RevTeX 2.0 macros
Nonlinear Dynamics in Distributed Systems
We build on a previous statistical model for distributed systems and
formulate it in a way that the deterministic and stochastic processes within
the system are clearly separable. We show how internal fluctuations can be
analysed in a systematic way using Van Kanpen's expansion method for Markov
processes. We present some results for both stationary and time-dependent
states. Our approach allows the effect of fluctuations to be explored,
particularly in finite systems where such processes assume increasing
importance.Comment: Two parts: 8 pages LaTeX file and 5 (uuencoded) figures in Postscript
forma
Renormalization Group Evolution in the type I + II seesaw model
We carefully analyze the renormalization group equations in the type I + II
seesaw scenario in the extended standard model (SM) and minimal supersymmetric
standard model (MSSM). Furthermore, we present analytic formulae of the mixing
angles and phases and discuss the RG effect on the different mixing parameters
in the type II seesaw scenario. The renormalization group equations of the
angles have a contribution which is proportional to the mass squared difference
for a hierarchical spectrum. This is in contrast to the inverse proportionality
to the mass squared difference in the effective field theory case.Comment: 13 pages, 4 figures; corrected error due to wrong superfield
normalization in RG equations (24-28,C1-4) as well as error in RG equations
of mixing parameters (38,43); RG equations of mixing angles depend on
Majorana phase
A left-right symmetric model with SU(2)-triplet fermions
We consider an
left-right symmetric model with three Higgs scalars including an
doublet, an doublet and an bidoublet. In
addition to usual SU(2)-doublet fermions, our model contains SU(2)-triplet
fermions with Majorana masses. The neutral components of the left-handed
triplets can contribute a canonical seesaw while the neutral components of the
right-handed triplets associated with the right-handed neutrinos can contribute
a double/inverse-type seesaw. Our model can be embedded into an SO(10) grand
unification theory where the triplets belong to the representations.Comment: 4 pages. To appear in Phys. Rev.
TeV leptogenesis in Z-prime models and its collider probe
We show that the U(1)-prime models linked with the seesaw mechanism at TeV
scale can lead to a successful baryogenesis through soft leptogenesis with a
resonant behavior in the B parameter. Such a consideration constrains the
Z-prime mass to be larger than 2-3 TeV depending on the seesaw scale and the
spharelon rate. Together with multi-TeV Z-prime, large sneutrino-antisneutrino
mixing and CP violating phenomena required by TeV leptogenesis could be
searched for in future colliders by observing the distinct same-sign
dilepton--dichargino as well as dislepton--diHiggs signatures.Comment: 10 pages with 2 figure
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