Strongly Interacting Dynamics beyond the Standard Model on a Spacetime Lattice

Strong theoretical arguments suggest that the Higgs sector of the Standard Model of the Electroweak interactions is an effective low-energy theory, with a more fundamental theory that is expected to emerge at an energy scale of the order of the TeV. One possibility is that the more fundamental theory be strongly interacting and the Higgs sector be given by the low-energy dynamics of the underlying theory. We review recent works aimed to determining observable quantities by numerical simulations of strongly interacting theories proposed in the literature for explaining the Electroweak symmetry breaking mechanism. These investigations are based on Monte Carlo simulations of the theory formulated on a spacetime lattice. We focus on the so-called Minimal Walking Technicolour scenario, a SU(2) gauge theory with two flavours of fermions in the adjoint representation. The emerging picture is that this theory has an infrared fixed point that dominates the large distance physics. We shall discuss the first numerical determinations of quantities of phenomenological interest for this theory and analyse future directions of quantitative studies of strongly interacting beyond the Standard Model theories with Lattice techniques. In particular, we report on a finite size scaling determination of the chiral condensate anomalous dimension $\gamma$, for which we find $0.05 \le \gamma \le 0.25$.Comment: Minor corrections and clarifications of some points, conclusions unchange

Energy-dependent quenching adjusts the excitation diffusion length to regulate photosynthetic light harvesting

An important determinant of crop yields is the regulation of photosystem II (PSII) light harvesting by energy-dependent quenching (qE). However, the molecular details of excitation quenching have not been quantitatively connected to the PSII yield, which only emerges on the 100 nm scale of the grana membrane and determines flux to downstream metabolism. Here, we incorporate excitation dissipation by qE into a pigment-scale model of excitation transfer and trapping for a 200 nm x 200 nm patch of the grana membrane. We demonstrate that single molecule measurements of qE are consistent with a weak-quenching regime. Consequently, excitation transport can be rigorously coarse-grained to a 2D random walk with an excitation diffusion length determined by the extent of quenching. A diffusion-corrected lake model substantially improves the PSII yield determined from variable chlorophyll fluorescence measurements and offers an improved model of PSII for photosynthetic metabolism.Comment: 19 pages, 4 figures, 3 supplementary figure

Target Premia and Exchange Rates: Australian Evidence

This paper documents exchange rate and cross-border effects on Australian target premia. A significant relationship between changes in the real exchange rate and target premia for successful domestic and crossborder acquisitions is identified and shown to be robust to bid characteristics and relatedness of bidder and target. Exchange rate effects on domestic target premia are sensitive to measurement of the exchange rate and to the level of economic exposure experienced by the target. However, exchange rate and US crossborder effect on cross-border acquired targets are robust to model specifications and various definitions of the real and nominal exchange rate

Asymptotic analysis of silicon based Bragg fibers

We developed an asymptotic formalism that fully characterizes the propagation and loss properties of a Bragg fiber with finite cladding layers. The formalism is subsequently applied to miniature air-core Bragg fibers with Silicon-based cladding mirrors. The fiber performance is analyzed as a function of the Bragg cladding geometries, the core radius and the material absorption. The problems of fiber core deformation and other defects in Bragg fibers are also addressed using a finite-difference time-domain analysis and a Gaussian beam approximation, respectively

Creutz Ratios From Color-Truncated Lattice Configurations

We investigate whether information about Creutz ratios is encoded, separately, in each gluon color component of numerically generated lattice configurations. Working in SU(2) lattice gauge theory in Landau gauge, we set two of the three gluon color components to zero, and compensate for the loss of two-thirds of the fluctuation by simply rescaling the remaining component by a factor of $\sqrt{3}$. Creutz ratios are then computed with this "abelianized" configuration. We find that the Creutz ratios of loops constructed from abelianized links converge to the usual Creutz ratios in the scaling regime.Comment: 5 pages, plain LaTeX, one figur

Resummation of Large Endpoint Corrections to Color-Octet J/psi Photoproduction

An unresolved problem in J/psi phenomenology is a systematic understanding of the differential photoproduction cross section, dsigma/dz [gamma + p -> J/psi + X], where z= E_psi/E_gamma in the proton rest frame. In the non-relativistic QCD (NRQCD) factorization formalism, fixed-order perturbative calculations of color-octet mechanisms suffer from large perturbative and nonperturbative corrections that grow rapidly in the endpoint region, z -> 1. In this paper, NRQCD and soft collinear effective theory are combined to resum these large corrections to the color-octet photoproduction cross section. We derive a factorization theorem for the endpoint differential cross section involving the parton distribution function and the color-octet J/psi shape functions. A one loop matching calculation explicitly confirms our factorization theorem at next-to-leading order. Large perturbative corrections are resummed using the renormalization group. The calculation of the color-octet contribution to dsigma/dz is in qualitative agreement with data. Quantitative tests of the universality of color-octet matrix elements require improved knowledge of shape functions entering these calculations as well as resummation of the color-singlet contribution which accounts for much of the total cross section and also peaks near the endpoint.Comment: 30 pages, 6 figure

Modal analysis of Bragg onion resonators

From analysis of the high Q modes in a Bragg onion resonator with an omnidirectional reflector cladding, we establish a close analogy between such a resonator and a spherical hollow cavity in perfect metal. We demonstrate that onion resonators are ideal for applications that require a large spontaneous-emission factor ß, such as thresholdless lasers and single-photon devices