Performance Analysis of a Dual-Hop Cooperative Relay Network with Co-Channel Interference

This paper analyzes the performance of a dual-hop amplify-and-forward (AF) cooperative relay network in the presence of direct link between the source and destination and multiple co-channel interferences (CCIs) at the relay. Specifically, we derive the new analytical expressions for the moment generating function (MGF) of the output signal-to-interference-plus-noise ratio (SINR) and the average symbol error rate (ASER) of the relay network. Computer simulations are given to confirm the validity of the analytical results and show the effects of direct link and interference on the considered AF relay network

Non-Fermi liquid states in the pressurized CeCu2(Si1−xGex)2CeCu_2(Si_{1-x}Ge_x)_2 system: two critical points

In the archetypal strongly correlated electron superconductor CeCu$_2$Si$_2$ and its Ge-substituted alloys CeCu$_2$(Si$_{1-x}$Ge$_{x}$)$_2$ two quantum phase transitions -- one magnetic and one of so far unknown origin -- can be crossed as a function of pressure \cite{Yuan 2003a}. We examine the associated anomalous normal state by detailed measurements of the low temperature resistivity ($\rho$) power law exponent $\alpha$. At the lower critical point (at $p_{c1}$, $1\leq\alpha\leq 1.5$) $\alpha$ depends strongly on Ge concentration $x$ and thereby on disorder level, consistent with a Hlubina-Rice-Rosch scenario of critical scattering off antiferromagnetic fluctuations. By contrast, $\alpha$ is independent of $x$ at the upper quantum phase transition (at $p_{c2}$, $\alpha\simeq 1$), suggesting critical scattering from local or Q=0 modes, in agreement with a density/valence fluctuation approach.Comment: 4 pages, including 4 figures. New results added. Significant changes on the text and Fig.

Single top production in the tt-channel at LHC: a realistic test of electroweak models

We compute the complete electroweak one-loop effect on the process of $t$-channel single top production at LHC in the Standard Model and in the MSSM within the mSUGRA symmetry breaking scheme. We find that the one-loop electroweak SM effect is large, and decreases the cross section of an amount that is of the same size as that of the NLO QCD one. The genuine SUSY effect in the mSUGRA scheme, for a general choice of benchmark points, is rather small. It might become large and visible in more general scenarios around thresholds involving light stop and neutralino mass values.Comment: 28 pages, 10 eps figure

q_T Uncertainties for W and Z Production

Analysis of semi-inclusive DIS hadroproduction suggests broadening of transverse momentum distributions at small x below 1E-3 ~ 1E-2 which can be modeled in the Collins-Soper-Sterman formalism by a modification of impact parameter dependent parton densities. We investigate these consequences for the production of electroweak bosons at the Tevatron and the LHC. If substantial small-x broadening is observed in forward Z boson production in the Tevatron Run-2, it will strongly affect the predicted q_T distributions for W and Z boson production at the LHC.Comment: 4 pages, 2 figures; contribution to the XIII International Workshop on Deep Inelastic Scattering (DIS 2005

Optimal vaccination in a stochastic epidemic model of two non-interacting populations

Developing robust, quantitative methods to optimize resource allocations in response to epidemics has the potential to save lives and minimize health care costs. In this paper, we develop and apply a computationally efficient algorithm that enables us to calculate the complete probability distribution for the final epidemic size in a stochastic Susceptible-Infected-Recovered (SIR) model. Based on these results, we determine the optimal allocations of a limited quantity of vaccine between two non-interacting populations. We compare the stochastic solution to results obtained for the traditional, deterministic SIR model. For intermediate quantities of vaccine, the deterministic model is a poor estimate of the optimal strategy for the more realistic, stochastic case.Comment: 21 pages, 7 figure

Stability of Transonic Characteristic Discontinuities in Two-Dimensional Steady Compressible Euler Flows

For a two-dimensional steady supersonic Euler flow past a convex cornered wall with right angle, a characteristic discontinuity (vortex sheet and/or entropy wave) is generated, which separates the supersonic flow from the gas at rest (hence subsonic). We proved that such a transonic characteristic discontinuity is structurally stable under small perturbations of the upstream supersonic flow in $BV$. The existence of a weak entropy solution and Lipschitz continuous free boundary (i.e. characteristic discontinuity) is established. To achieve this, the problem is formulated as a free boundary problem for a nonstrictly hyperbolic system of conservation laws; and the free boundary problem is then solved by analyzing nonlinear wave interactions and employing the front tracking method.Comment: 26 pages, 3 figure

Origin of the X-ray Emission in the Nuclei of FR Is

We investigate the X-ray origin in FRIs using the multi-waveband high resolution data of eight FR I sources, which have very low Eddington ratios. We fit their multi-waveband spectrum using a coupled accretion-jet model. We find that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is from the advection-dominated accretion flow (ADAF). Four sources with moderate L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is from the jet, and the other three is from the sum of the jet and ADAF. The X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is dominated by the jet. These results roughly support the predictions of Yuan and Cui(2005) where they predict that when the X-ray luminosity of the system is below a critical value, the X-radiation will not be dominated by the emission from the ADAF any longer, but by the jet. We also find that the accretion rates in four sources must be higher than the Bondi rates, which implies that other fuel supply (e.g., stellar winds) inside the Bondi radius should be important.Comment: 6 pages. To published in Journal of Physics, in proceedings of "The Universe under the Microscope - Astrophysics at High Angular Resolution" (Bad Honnef, Germany, April 2008), eds. R. Schoedel, A. Eckart, S. Pfalzner, and E. Ro

B-meson signatures of a Supersymmetric U(2) flavor model

We discuss B-meson signatures of a Supersymmetric U(2) flavor model, with relatively light (electroweak scale masses) third generation right-handed scalars. We impose current B and K meson experimental constraints on such a theory, and obtain expectations for B->X_s gamma, B->X_s glue, B->X_s l+ l-, B->phi K_s, B_s-B_sbar mixing, and the dilepton asymmetry in B_s. We show that such a theory is compatible with all current data, and furthermore, could reconcile the apparent deviations from Standard Model predictions that have been found in some experiments.Comment: 37 pages, 21 figures, RevTeX4; v.2 - minor modifications to improve readability. Published versio