63 research outputs found
Nonlinear Localization in Metamaterials
Metamaterials, i.e., artificially structured ("synthetic") media comprising
weakly coupled discrete elements, exhibit extraordinary properties and they
hold a great promise for novel applications including super-resolution imaging,
cloaking, hyperlensing, and optical transformation. Nonlinearity adds a new
degree of freedom for metamaterial design that allows for tuneability and
multistability, properties that may offer altogether new functionalities and
electromagnetic characteristics. The combination of discreteness and
nonlinearity may lead to intrinsic localization of the type of discrete
breather in metallic, SQUID-based, and symmetric metamaterials. We
review recent results demonstrating the generic appearance of breather
excitations in these systems resulting from power-balance between intrinsic
losses and input power, either by proper initialization or by purely dynamical
procedures. Breather properties peculiar to each particular system are
identified and discussed. Recent progress in the fabrication of low-loss,
active and superconducting metamaterials, makes the experimental observation of
breathers in principle possible with the proposed dynamical procedures.Comment: 19 pages, 14 figures, Invited (Review) Chapte
B-L Cosmic Strings in Heterotic Standard Models
E_{8} X E_{8} heterotic string and M-theory, when compactified on smooth
Calabi-Yau manifolds with SU(4) vector bundles, can give rise to softly broken
N=1 supersymmetric theories with the exact matter spectrum of the MSSM,
including three right-handed neutrinos and one Higgs-Higgs conjugate pair of
supermultiplets. These vacua have the SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge
group of the standard model augmented by an additional gauged U(1)_{B-L}. Their
minimal content requires that the B-L symmetry be spontaneously broken by a
vacuum expectation value of at least one right-handed sneutrino. The soft
supersymmetry breaking operators can induce radiative breaking of the B-L gauge
symmetry with an acceptable B-L/electroweak hierarchy. In this paper, it is
shown that U(1)_{B-L} cosmic strings occur in this context, potentially with
both bosonic and fermionic superconductivity. We present a numerical analysis
that demonstrates that boson condensates can, in principle, form for theories
of this type. However, the weak Yukawa and gauge couplings of the right-handed
sneutrino suggests that bosonic superconductivity will not occur in the
simplest vacua in this context. The electroweak phase transition also disallows
fermion superconductivity, although substantial bound state fermion currents
can exist.Comment: 41 pages, 5 figure
Testing Yukawa-unified SUSY during year 1 of LHC: the role of multiple b-jets, dileptons and missing E_T
We examine the prospects for testing SO(10) Yukawa-unified supersymmetric
models during the first year of LHC running at \sqrt{s}= 7 TeV, assuming
integrated luminosity values of 0.1 to 1 fb^-1. We consider two cases: the
Higgs splitting (HS) and the D-term splitting (DR3) models. Each generically
predicts light gluinos and heavy squarks, with an inverted scalar mass
hierarchy. We hence expect large rates for gluino pair production followed by
decays to final states with large b-jet multiplicity. For 0.2 fb^-1 of
integrated luminosity, we find a 5 sigma discovery reach of m(gluino) ~ 400 GeV
even if missing transverse energy, E_T^miss, is not a viable cut variable, by
examining the multi-b-jet final state. A corroborating signal should stand out
in the opposite-sign (OS) dimuon channel in the case of the HS model; the DR3
model will require higher integrated luminosity to yield a signal in the OS
dimuon channel. This region may also be probed by the Tevatron with 5-10 fb^-1
of data, if a corresponding search in the multi-b+ E_T^miss channel is
performed. With higher integrated luminosities of ~1 fb^-1, using E_T^miss plus
a large multiplicity of b-jets, LHC should be able to discover Yukawa-unified
SUSY with m(gluino) up to about 630 GeV. Thus, the year 1 LHC reach for
Yukawa-unified SUSY should be enough to either claim a discovery of the gluino,
or to very nearly rule out this class of models, since higher values of
m(gluino) lead to rather poor Yukawa unification.Comment: 32 pages including 31 EPS figure
PT-Symmetric Dimer in a Generalized Model of Coupled Nonlinear Oscillators
Abstract In the present work, we explore the case of a general PT -symmetric dimer in the context of two both linearly and nonlinearly coupled cubic oscillators. To obtain an analytical handle on the system, we first explore the rotating wave approximation converting it into a discrete nonlinear Schrödinger type dimer. In the latter context, the stationary solutions and their stability are identified numerically but also wherever possible analytically. Solutions stemming from both symmetric and anti-symmetric special limits are identified. A number of special cases are explored regarding the ratio of coefficients of nonlinearity between oscillators over the intrinsic one of each oscillator. Finally, the considerations are extended to the original oscillator model, where periodic orbits and their stability are obtained. When the solutions are found to be unstable their dynamics is monitored by means of direct numerical simulations
Hydrogen Sulfide Protects against Chemical Hypoxia-Induced Cytotoxicity and Inflammation in HaCaT Cells through Inhibition of ROS/NF-κB/COX-2 Pathway
Hydrogen sulfide (H2S) has been shown to protect against oxidative stress injury and inflammation in various hypoxia-induced insult models. However, it remains unknown whether H2S protects human skin keratinocytes (HaCaT cells) against chemical hypoxia-induced damage. In the current study, HaCaT cells were treated with cobalt chloride (CoCl2), a well known hypoxia mimetic agent, to establish a chemical hypoxia-induced cell injury model. Our findings showed that pretreatment of HaCaT cells with NaHS (a donor of H2S) for 30 min before exposure to CoCl2 for 24 h significantly attenuated CoCl2-induced injuries and inflammatory responses, evidenced by increases in cell viability and GSH level and decreases in ROS generation and secretions of IL-1β, IL-6 and IL-8. In addition, pretreatment with NaHS markedly reduced CoCl2-induced COX-2 overexpression and PGE2 secretion as well as intranuclear NF-κB p65 subunit accumulation (the central step of NF-κB activation). Similar to the protective effect of H2S, both NS-398 (a selective COX-2 inhibitor) and PDTC (a selective NF-κB inhibitor) depressed not only CoCl2-induced cytotoxicity, but also the secretions of IL-1β, IL-6 and IL-8. Importantly, PDTC obviously attenuated overexpression of COX-2 induced by CoCl2. Notably, NAC, a ROS scavenger, conferred a similar protective effect of H2S against CoCl2-induced insults and inflammatory responses. Taken together, the findings of the present study have demonstrated for the first time that H2S protects HaCaT cells against CoCl2-induced injuries and inflammatory responses through inhibition of ROS-activated NF-κB/COX-2 pathway
Constraints on exotic lepton doublets with minimal coupling to the standard model
We investigate the consequences of introducing a set of exotic doublet
leptons which couple to the standard model leptons in a minimal way. Through
these additional gauge invariant and renormalizable coupling terms, new sources
of tree-level flavor changing currents are induced via mixing. In this work, we
derive constraints on the parameters that govern the couplings to the exotic
doublets by invoking the current low-energy experimental data on processes such
as leptonic Z decays, , , and - conversion in atomic nuclei. Moreover, we have analyzed
the role these doublets play on the lepton anomalous magnetic moments, and
found that their contribution is negligible.Comment: 18 pages, 1 figure, 2 tables (REVTeX4.1); v2: added discussions in
Sec.II, III & IX and new ref. To appear in JHEP. arXiv admin note: text
overlap with arXiv:1011.473
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