938,931 research outputs found
Minimal model theory for log surfaces
We discuss the log minimal model theory for log surfaces. We show that the
log minimal model program, the finite generation of log canonical rings, and
the log abundance theorem for log surfaces hold true under assumptions weaker
than the usual framework of the log minimal model theory.Comment: 34 pages, v2: Section 8 is new, v3: minor revisio
Fermion Hierarchy from Sfermion Anarchy
We present a framework to generate the hierarchical flavor structure of
Standard Model quarks and leptons from loops of superpartners. The simplest
model consists of the minimal supersymmetric standard model with tree level
Yukawa couplings for the third generation only and anarchic squark and slepton
mass matrices. Agreement with constraints from low energy flavor observables,
in particular Kaon mixing, is obtained for supersymmetric particles with masses
at the PeV scale or above. In our framework both the second and the first
generation fermion masses are generated at 1-loop. Despite this, a novel
mechanism generates a hierarchy among the first and second generations without
imposing a symmetry or small parameters. A second-to-first generation mass
ratio of order 100 is typical. The minimal supersymmetric standard model thus
includes all the necessary ingredients to realize a fermion spectrum that is
qualitatively similar to observation, with hierarchical masses and mixing. The
minimal framework produces only a few quantitative discrepancies with
observation, most notably the muon mass is too low. We discuss simple
modifications which resolve this and also investigate the compatibility of our
model with gauge and Yukawa coupling Unification.Comment: 42 pages, 11 figure
Automated mass spectrum generation for new physics
We describe an extension of the FeynRules package dedicated to the automatic
generation of the mass spectrum associated with any Lagrangian-based quantum
field theory. After introducing a simplified way to implement particle mixings,
we present a new class of FeynRules functions allowing both for the analytical
computation of all the model mass matrices and for the generation of a C++
package, dubbed ASperGe. This program can then be further employed for a
numerical evaluation of the rotation matrices necessary to diagonalize the
field basis. We illustrate these features in the context of the
Two-Higgs-Doublet Model, the Minimal Left-Right Symmetric Standard Model and
the Minimal Supersymmetric Standard Model.Comment: 11 pages, 1 table; version accepted by EPJ
Prediction and Generation of Binary Markov Processes: Can a Finite-State Fox Catch a Markov Mouse?
Understanding the generative mechanism of a natural system is a vital
component of the scientific method. Here, we investigate one of the fundamental
steps toward this goal by presenting the minimal generator of an arbitrary
binary Markov process. This is a class of processes whose predictive model is
well known. Surprisingly, the generative model requires three distinct
topologies for different regions of parameter space. We show that a previously
proposed generator for a particular set of binary Markov processes is, in fact,
not minimal. Our results shed the first quantitative light on the relative
(minimal) costs of prediction and generation. We find, for instance, that the
difference between prediction and generation is maximized when the process is
approximately independently, identically distributed.Comment: 12 pages, 12 figures;
http://csc.ucdavis.edu/~cmg/compmech/pubs/gmc.ht
Vacuum Stability in the Early Universe and the Backreaction of Classical Gravity
In the case of a metastable electroweak vacuum the quantum corrected
effective potential plays a crucial role in the potential instability of the
Standard Model. In the Early Universe, in particular during inflation and
reheating, this instability can be triggered leading to catastrophic vacuum
decay. We discuss how the large spacetime curvature of the Early Universe can
be incorporated in the calculation and in many cases significantly modify the
flat space prediction. The two key new elements are the unavoidable generation
of the non-minimal coupling between the Higgs field and the scalar curvature of
gravity and a curvature induced contribution to the running of the constants.
For the minimal set up of the Standard Model and a decoupled inflation sector
we show how a metastable vacuum can lead to very tight bounds for the
non-minimal coupling. We also discuss a novel and very much related dark matter
generation mechanism.Comment: 12 pages, 6 figures, 1 table. Proceedings for the meeting 'Higgs
Cosmology' (27-28.3.2017). An updated version was accepted for publication at
Philos. Trans.
GRACE/SUSY Automatic Generation of Tree Amplitudes in the Minimal Supersymmetric Standard Model
GRACE/SUSY is a program package for generating the tree-level amplitude and
evaluating the corresponding cross section of processes of the minimal
supersymmetric extension of the standard model (MSSM). The Higgs potential
adopted in the system, however, is assumed to have a more general form
indicated by the two-Higgs-doublet model. This system is an extension of GRACE
for the standard model(SM) of the electroweak and strong interactions. For a
given MSSM process the Feynman graphs and amplitudes at tree-level are
automatically created. The Monte-Carlo phase space integration by means of
BASES gives the total and differential cross sections. When combined with
SPRING, an event generator, the program package provides us with the simulation
of the SUSY particle productions.Comment: 39 page, 1 figur
A Simple and Realistic Model of Supersymmetry Breaking
We present a simple and realistic model of supersymmetry breaking. In
addition to the minimal supersymmetric standard model, we only introduce a
hidden sector gauge group SU(5) and three fields X, F and \bar{F}.
Supersymmetry is broken at a local minimum of the potential, and its effects
are transmitted to the supersymmetric standard model sector through both
standard model gauge loops and local operators suppressed by the cutoff scale,
which is taken to be the unification scale. The form of the local operators is
controlled by a U(1) symmetry. The generated supersymmetry breaking and mu
parameters are comparable in size, and no flavor or CP violating terms arise.
The spectrum of the first two generation superparticles is that of minimal
gauge mediation with the number of messengers N_mess = 5 and the messenger
scale 10^11 GeV < M_mess < 10^13 GeV. The spectrum of the Higgs bosons and
third generation superparticles, however, can deviate from it. The lightest
supersymmetric particle is the gravitino with a mass of order (1-10) GeV.Comment: 19 pages, version to appear in Phys. Lett.
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