18,037 research outputs found
Tangential Extremal Principles for Finite and Infinite Systems of Sets, I: Basic Theory
In this paper we develop new extremal principles in variational analysis that
deal with finite and infinite systems of convex and nonconvex sets. The results
obtained, unified under the name of tangential extremal principles, combine
primal and dual approaches to the study of variational systems being in fact
first extremal principles applied to infinite systems of sets. The first part
of the paper concerns the basic theory of tangential extremal principles while
the second part presents applications to problems of semi-infinite programming
and multiobjective optimization
Tangential Extremal Principles for Finite and Infinite Systems of Sets, II: Applications to Semi-infinite and Multiobjective Optimization
This paper contains selected applications of the new tangential extremal
principles and related results developed in Part I to calculus rules for
infinite intersections of sets and optimality conditions for problems of
semi-infinite programming and multiobjective optimization with countable
constraint
Rated Extremal Principles for Finite and Infinite Systems
In this paper we introduce new notions of local extremality for finite and
infinite systems of closed sets and establish the corresponding extremal
principles for them called here rated extremal principles. These developments
are in the core geometric theory of variational analysis. We present their
applications to calculus and optimality conditions for problems with infinitely
many constraints
On the threshold-width of graphs
The GG-width of a class of graphs GG is defined as follows. A graph G has
GG-width k if there are k independent sets N1,...,Nk in G such that G can be
embedded into a graph H in GG such that for every edge e in H which is not an
edge in G, there exists an i such that both endpoints of e are in Ni. For the
class TH of threshold graphs we show that TH-width is NP-complete and we
present fixed-parameter algorithms. We also show that for each k, graphs of
TH-width at most k are characterized by a finite collection of forbidden
induced subgraphs
The Big Bang and Inflation United by an Analytic Solution
Exact analytic solutions for a class of scalar-tensor gravity theories with a
hyperbolic scalar potential are presented. Using an exact solution we have
successfully constructed a model of inflation that produces the spectral index,
the running of the spectral index and the amplitude of scalar perturbations
within the constraints given by the WMAP 7 years data. The model simultaneously
describes the Big Bang and inflation connected by a specific time delay between
them so that these two events are regarded as dependent on each other. In
solving the Fridemann equations, we have utilized an essential Weyl symmetry of
our theory in 3+1 dimensions which is a predicted remaining symmetry of
2T-physics field theory in 4+2 dimensions. This led to a new method of
obtaining analytic solutions in 1T field theory which could in principle be
used to solve more complicated theories with more scalar fields. Some
additional distinguishing properties of the solution includes the fact that
there are early periods of time when the slow roll approximation is not valid.
Furthermore, the inflaton does not decrease monotonically with time, rather it
oscillates around the potential minimum while settling down, unlike the slow
roll approximation. While the model we used for illustration purposes is
realistic in most respects, it lacks a mechanism for stopping inflation. The
technique of obtaining analytic solutions opens a new window for studying
inflation, and other applications, more precisely than using approximations.Comment: V2 improve computation with better agreement with WMAP 7 years data,
and also point out an exact solution for cyclic cosmolog
Numerical study of large-eddy breakup and its effect on the drag characteristics of boundary layers
The break-up of a field of eddies by a flat-plate obstacle embedded in a boundary layer is studied using numerical solutions to the two-dimensional Navier-Stokes equations. The flow is taken to be incompressible and unsteady. The flow field is initiated from rest. A train of eddies of predetermined size and strength are swept into the computational domain upstream of the plate. The undisturbed velocity profile is given by the Blasius solution. The disturbance vorticity generated at the plate and wall, plus that introduced with the eddies, mix with the background vorticity and is transported throughout the entire flow. All quantities are scaled by the plate length, the unidsturbed free-stream velocity, and the fluid kinematic viscosity. The Reynolds number is 1000, the Blasius boundary layer thickness is 2.0, and the plate is positioned a distance of 1.0 above the wall. The computational domain is four units high and sixteen units long
Two-Higgs-Doublet type-II and -III models and at the LHC
We study the constraints of the generic two-Higgs-doublet model (2HDM)
type-III and the impacts of the new Yukawa couplings. For comparisons, we
revisit the analysis in the 2HDM type-II. To understand the influence of all
involving free parameters and to realize their correlations, we employ
-square fitting approach by including theoretical and experimental
constraints, such as S, T, and U oblique parameters, the production of standard
model Higgs and its decay to , , , etc.
The errors of analysis are taken at , , and confidence
levels. Due to the new Yukawa couplings being associated with
and , we find that the allowed
regions for and in the type-III model can be broader
when the dictated parameter is positive; however, for negative
, the limits are stricter than those in the type-II model. By using the
constrained parameters, we find that the deviation from the SM in the can be of . Additionally, we also study the top-quark
flavor-changing processes induced at the tree level in the type-III model and
find that when all current experimental data are considered, we get for and GeV and
slightly exceeds for GeV.Comment: 22 pages, 11 figures. v3: Slight change in the abstract, Figure.1
added and commented, the conclusion remains unchange
Complete Set of Homogeneous Isotropic Analytic Solutions in Scalar-Tensor Cosmology with Radiation and Curvature
We study a model of a scalar field minimally coupled to gravity, with a
specific potential energy for the scalar field, and include curvature and
radiation as two additional parameters. Our goal is to obtain analytically the
complete set of configurations of a homogeneous and isotropic universe as a
function of time. This leads to a geodesically complete description of the
universe, including the passage through the cosmological singularities, at the
classical level. We give all the solutions analytically without any
restrictions on the parameter space of the model or initial values of the
fields. We find that for generic solutions the universe goes through a singular
(zero-size) bounce by entering a period of antigravity at each big crunch and
exiting from it at the following big bang. This happens cyclically again and
again without violating the null energy condition. There is a special subset of
geodesically complete non-generic solutions which perform zero-size bounces
without ever entering the antigravity regime in all cycles. For these, initial
values of the fields are synchronized and quantized but the parameters of the
model are not restricted. There is also a subset of spatial curvature-induced
solutions that have finite-size bounces in the gravity regime and never enter
the antigravity phase. These exist only within a small continuous domain of
parameter space without fine tuning initial conditions. To obtain these
results, we identified 25 regions of a 6-parameter space in which the complete
set of analytic solutions are explicitly obtained.Comment: 38 pages, 29 figure
Exotic fermion multiplets as a solution to baryon asymmetry, dark matter and neutrino masses
We propose an extension to the standard model where three exotic fermion
5-plets and one scalar 6-plet are added to the particle content. By demanding
that all interactions are renormalizable and standard model gauge invariant, we
show that the lightest exotic particle in this model can be a dark matter
candidate as long as the new 6-plet scalar does not develop a nonzero vacuum
expectation value. Furthermore, light neutrino masses are generated radiatively
at one-loop while the baryon asymmetry is produced by the CP-violating decays
of the second lightest exotic particle. We have demonstrated using concrete
examples that there is a parameter space where a consistent solution to the
problems of baryon asymmetry, dark matter and neutrino masses can be obtained.Comment: 17 pages, 2 figures (REVTeX4.1), v2: some refs added, v3: typos
corrected, Sec.VI.B, C modified, this version to appear in PR
Use of cystatin C to inform metformin eligibility among adult veterans with diabetes.
AimsRecommendations for metformin use are dependent on eGFR category: eGFR >45 ml/min/1.73 m2 - "first-line agent"; eGFR 30-44 - "use with caution"; eGFR<30 - "do not use". Misclassification of metformin eligibility by creatinine-based MDRD GFR estimates (eGFRcr) may contribute to its misuse. We investigated the impact of cystatin c estimates of GFR (eGFRcys) on metformin eligibility.MethodsIn a consecutive cohort of 550 Veterans with diabetes, metformin use and eligibility were assessed by eGFR category, using eGFRcr and eGFRcys. Discrepancy in eligibility was defined as cases where eGFRcr and eGFRcys categories (<30, 30-44, 45-60, and >60 ml/min/1.73 m2) differed with an absolute difference in eGFR of >5 ml/min/1.73 m2. We modeled predictors of metformin use and eGFR category discrepancy with multivariable relative risk regression and multinomial logistic regression.ResultsSubjects were 95% male, median age 68, and racially diverse (45% White, 22% Black, 11% Asian, 22% unknown). Metformin use decreased with severity of eGFRcr category, from 63% in eGFRcr >60 to 3% in eGFRcr <30. eGFRcys reclassified 20% of Veterans into different eGFR categories. Factors associated with a more severe eGFRcys category compared to eGFRcr were older age (aOR = 2.21 per decade, 1.44-1.82), higher BMI (aOR = 1.04 per kg/m2, 1.01-1.08) and albuminuria >30 mg/g (aOR = 1.81, 1.20-2.73).ConclusionsMetformin use is low among Veterans with CKD. eGFRcys may serve as a confirmatory estimate of kidney function to allow safe use of metformin among patients with CKD, particularly among older individuals and those with albuminuria
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