Incompatible sets of gradients and metastability

We give a mathematical analysis of a concept of metastability induced by incompatibility. The physical setting is a single parent phase, just about to undergo transformation to a product phase of lower energy density. Under certain conditions of incompatibility of the energy wells of this energy density, we show that the parent phase is metastable in a strong sense, namely it is a local minimizer of the free energy in an $L^1$ neighbourhood of its deformation. The reason behind this result is that, due to the incompatibility of the energy wells, a small nucleus of the product phase is necessarily accompanied by a stressed transition layer whose energetic cost exceeds the energy lowering capacity of the nucleus. We define and characterize incompatible sets of matrices, in terms of which the transition layer estimate at the heart of the proof of metastability is expressed. Finally we discuss connections with experiment and place this concept of metastability in the wider context of recent theoretical and experimental research on metastability and hysteresis.Comment: Archive for Rational Mechanics and Analysis, to appea

On Two-Body Decays of A Scalar Glueball

We study two body decays of a scalar glueball. We show that in QCD a spin-0 pure glueball (a state only with gluons) cannot decay into a pair of light quarks if chiral symmetry holds exactly, i.e., the decay amplitude is chirally suppressed. However, this chiral suppression does not materialize itself at the hadron level such as in decays into $\pi^+\pi^-$ and $K^+K^-$, because in perturbative QCD the glueball couples to two (but not one) light quark pairs that hadronize to two mesons. Using QCD factorization based on an effective Lagrangian, we show that the difference of hadronization into $\pi\pi$ and $KK$ already leads to a large difference between ${\rm Br} (\pi^+\pi^-)$ and ${\rm Br}(K^+K^-)$, even the decay amplitude is not chirally suppressed. Moreover, the small ratio of $R={\rm Br}(\pi\pi)/{\rm Br}(K\bar K)$ of $f_0(1710)$ measured in experiment does not imply $f_0(1710)$ to be a pure glueball. With our results it is helpful to understand the partonic contents if ${\rm Br}(\pi\pi)$ or ${\rm Br}(K\bar K)$ is measured reliably.Comment: revised versio

Exploring the Unitarity Triangle through CP violation observables in Bs→K+K−B_s \to K^+ K^-

We discuss the determination of the CKM parameters from the forthcoming $CP$ violation observables in $B_s \to K^+ K^-$ decays. Combining the information on mixing induced CP violation in $B_s \to K^+ K^-$, with the $B_d \to J/\psi K_s$ precision observable $\sin 2\beta$ and the $B^0_s$--$\bar{B^0_s}$ mixing phase $\phi_s$, we propose a determination of the unitarity triangle $(\bar\rho, \bar\eta)$. Computing the penguin parameters $(r, \theta)$ within QCD factorization yield precise determination of $(\bar\rho, \bar\eta)$, reflected by a weak dependence on the $\theta$ which is shown as a second order effect. The impact of the direct CP violation observable $C_{KK}$ on the penguin parameters are investigated and a lower bound on $C_{KK}$ is extracted. We also discuss the effect of the $B^0_s$--$\bar{B^0_s}$ new physics mixing phase on the penguin parameters $(r, \theta)$ and $S_{KK}$. Using the SU(3)-flavour symmetry argument and the current $B$-factories data provided by the $B_d \to \pi^+ \pi^-$ modes, we complement the $B_s \to K^+ K^-$ CP-violating observables in a variety of ways, in particular we find that $S_{KK}>0$. Finally we analyze systematically the SU(3)-symmetry breaking factor within QCD factorization.Comment: 22 pages, 6 figures, typos corrected, reference and some remarks adde

Jamming and Stress Propagation in Particulate Matter

We present simple models of particulate materials whose mechanical integrity arises from a jamming process. We argue that such media are generically "fragile", that is, they are unable to support certain types of incremental loading without plastic rearrangement. In such models, fragility is naturally linked to the marginal stability of force chain networks (granular skeletons) within the material. Fragile matter exhibits novel mechanical responses that may be relevant to both jammed colloids and cohesionless assemblies of poured, rigid grains.Comment: LATEX, 3 Figures, elsart.cls style file, 11 page

Immunization with a synthetic consensus hepatitis C virus E2 glycoprotein ectodomain elicits virus-neutralizing antibodies

Global eradication of hepatitis C virus (HCV) infection will require an efficacious vaccine capable of eliciting protective immunity against genetically diverse HCV strains. Natural spontaneous resolution of HCV infection is associated with production of broadly neutralizing antibodies targeting the HCV glycoproteins E1 and E2. As such, production of cross-neutralizing antibodies is an important endpoint for experimental vaccine trials. Varying success generating cross-neutralizing antibodies has been achieved with immunogens derived from naturally-occurring HCV strains. In this study the challenge of minimising the genetic diversity between the vaccine strain and circulating HCV isolates was addressed. Two novel synthetic E2 glycoprotein immunogens (NotC1 and NotC2) were derived from consensus nucleotide sequences deduced from samples of circulating genotype 1 HCV strains. These two synthetic sequences differed in their relative positions in the overall genotype 1a/1b phylogeny. Expression of these constructs in Drosophila melanogaster S2 cells resulted in high yields of correctly-folded, monomeric E2 protein, which were recognised by broadly neutralizing monoclonal antibodies. Immunization of guinea pigs with either of these consensus immunogens, or a comparable protein representing a circulating genotype 1a strain resulted in high titres of cross-reactive anti-E2 antibodies. All immunogens generated antibodies capable of neutralizing the H77 strain, but NotC1 elicited antibodies that more potently neutralized virus entry. These vaccine-induced antibodies neutralized some viruses representing genotype 1, but not strains representing genotype 2 or genotype 3. Thus, while this approach to vaccine design resulted in correctly folded, immunogenic protein, cross-neutralizing epitopes were not preferentially targeted by the host immune response generated by this immunogen. Greater immunofocussing by vaccines to common epitopes is necessary to successfully elicit broadly neutralizing antibodies

Some properties of the newly observed X(1835) state at BES

Recently the BES collaboration has announced observation of a resonant state in the $\pi^+\pi^- \eta'$ spectrum in $J/\psi \to \gamma \pi^+\pi^-\eta'$ decay. Fitting the data with a $0^{-+}$ state, the mass is determined to be 1833.7 MeV with $7.7\sigma$ statistic significance. This state is consistent with the one extracted from previously reported $p \bar p$ threshold enhancement data in $J/\psi \to \gamma p \bar p$. We study the properties of this state using QCD anomaly and QCD sum rules assuming X(1835) to be a pseudoscalar and show that it is consistent with data. We find that this state has a sizeable matrix element $$ leading to branching ratios of $(2.61\sim 7.37)\times 10^{-3}$ and $(2.21\sim 10.61)\times 10^{-2}$ for $J/\psi \to \gamma G_p$ and for $G_p \to \pi^+\pi^- \eta'$, respectively. Combining the calculated branching ratio of $J/\psi \to \gamma G_p$ and data on threshold enhancement in $J/\psi \to \gamma p \bar p$, we determine the coupling for $G_p- p-\bar p$ interaction. We finally study branching ratios of other $J/\psi \to \gamma + {three mesons}$ decay modes. We find that $J/\psi \to \gamma G_p \to \gamma (\pi^+\pi^- \eta, K K \pi^0)$ can provide useful tests for the mechanism proposed.Comment: 13 pages, 3 figures. The final version to appear at EPJ

Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules

Within the Standard Model, we investigate the weak decays of $\Lambda_b \to \Lambda + \gamma$ and $\Lambda_b \to \Lambda + l^{+} l^{-}$ with the light-cone sum rules approach. The higher twist distribution amplitudes of $\Lambda$ baryon to the leading conformal spin are included in the sum rules for transition form factors. Our results indicate that the higher twist distribution amplitudes almost have no influences on the transition form factors retaining the heavy quark spin symmetry, while such corrections can result in significant impacts on the form factors breaking the heavy quark spin symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of $\Lambda$ baryon are also employed in the sum rules for a comparison, which can give rise to the form factors approximately 5 times larger than that in terms of conformal expansion. Utilizing the form factors calculated in LCSR, we then perform a careful study on the decay rate, polarization asymmetry and forward-backward asymmetry, with respect to the decays of $\Lambda_b \to \Lambda \gamma$, $\Lambda l^{+}l^{-}$.Comment: 38 pages, 15 figures, some typos are corrected and more references are adde

A diverse panel of hepatitis C virus glycoproteins for use in vaccine research reveals extremes of monoclonal antibody neutralization resistance

Despite significant advances in the treatment of hepatitis C virus (HCV) infection, the need to develop preventative vaccines remains. Identification of the best vaccine candidates and evaluation of their performance in preclinical and clinical development will require appropriate neutralization assays utilizing diverse HCV isolates. We aimed to generate and characterize a panel of HCVE1E2 glycoproteins suitable for subsequent use in vaccine and therapeutic antibody testing. Full-length E1E2 clones were PCR amplified from patient- derived serum samples, cloned into an expression vector, and used to generate viral pseudoparticles (HCVpp). In addition, some of these clones were used to generate cell culture infectious (HCVcc) clones. The infectivity and neutralization sensitivity of these viruses were then determined. Bioinformatic and HCVpp infectivity screening of approximately 900 E1E2 clones resulted in the assembly of a panel of 78 functional E1E2 proteins representing distinct HCV genotypes and different stages of infection. These HCV glycoproteins differed markedly in their sensitivity to neutralizing antibodies. We used this panel to predict antibody efficacy against circulating HCV strains, highlighting the likely reason why some monoclonal antibodies failed in previous clinical trials. This study provides the first objective categorization of cross-genotype patient-derived HCVE1E2 clones according to their sensitivity to antibody neutralization. It has shown that HCV isolates have clearly distinguishable neutralization-sensitive, -resistant, or -intermediate phenotypes, which are independent of genotype. The panel provides a systematic means for characterization of the neutralizing response elicited by candidate vaccines and for defining the therapeutic potential of monoclonal antibodies

Allowed Gamow-Teller Excitations from the Ground State of 14N

Motivated by the proposed experiment $^{14}N(d,{^2He})^{14}C$, we study the final states which can be reached via the allowed Gamow-Teller mechanism. Much emphasis has been given in the past to the fact that the transition matrix element from the $J^{\pi}=1^+ T=0$ ground state of $^{14}N$ to the $J^{\pi}=0^+ T=1$ ground state of $^{14}C$ is very close to zero, despite the fact that all the quantum numbers are right for an allowed transition. We discuss this problem, but, in particular, focus on the excitations to final states with angular momenta $1^+$ and $2^+$. We note that the summed strength to the $J^{\pi}=2^+ T=1$ states, calculated with a wide variety of interactions, is significantly larger than that to the $J^{\pi}=1^+ T=1$ final states.Comment: Submitted to Phys. Rev.

A lattice study of the exclusive B→K∗γB \to K^* \gamma decay amplitude, using the Clover action at β=6.0\beta=6.0

We present the results of a numerical calculation of the $B\to K^* \gamma$ form factors. The results have been obtained by studying the relevant correlation functions at $\beta=6.0$, on an $18^3 \times 64$ lattice, using the ${\rm O(a)}$-improved fermion action, in the quenched approximation. From the study of the matrix element $$ we have obtained the form factor $T_1(0)$ which controls the exclusive decay rate. The results are compared with the recent results from CLEO. We also discuss the compatibility between the scaling laws predicted by the Heavy Quark Effective Theory (HQET) and pole dominance, by studying the mass- and $q^2$-dependence of the form factors. From our analysis, it appears that the form factors follow a mass behaviour compatible with the predictions of the HQET and that the $q^2$-dependence of $T_2$ is weaker than would be predicted by pole dominance.Comment: 17 pages, LaTeX + epsf.sty. Uuencoded, compressed, tar archive including the text and one postscript figur