119420110
High-accuracy critical exponents for O(N) hierarchical 3D sigma models
The critical exponent γ and its subleading exponent Δ in the 3D O(N) Dyson’s hierarchical model for N up to 20 are calculated with high accuracy. We calculate the critical temperatures for the measure δ(φ.φ − 1). We extract the first coefficients of the 1/N expansion from our numerical data. We show that the leading and subleading exponents agree with Polchinski equation and the equivalent Litim equation, in the local potential approximation, with at least 4 significant digits.
24114301
Discovery of a selective inhibitor of oncogenic B-Raf kinase with potent antimelanoma activity
BRAFV600E is the most frequent oncogenic protein kinase mutation known. Furthermore, inhibitors targeting “active” protein kinases have demonstrated significant utility in the therapeutic repertoire against cancer. Therefore, we pursued the development of specific kinase inhibitors targeting B-Raf, and the V600E allele in particular. By using a structure-guided discovery approach, a potent and selective inhibitor of active B-Raf has been discovered. PLX4720, a 7-azaindole derivative that inhibits B-RafV600E with an IC50 of 13 nM, defines a class of kinase inhibitor with marked selectivity in both biochemical and cellular assays. PLX4720 preferentially inhibits the active B-RafV600E kinase compared with a broad spectrum of other kinases, and potent cytotoxic effects are also exclusive to cells bearing the V600E allele. Consistent with the high degree of selectivity, ERK phosphorylation is potently inhibited by PLX4720 in B-RafV600E-bearing tumor cell lines but not in cells lacking oncogenic B-Raf. In melanoma models, PLX4720 induces cell cycle arrest and apoptosis exclusively in B-RafV600E-positive cells. In B-RafV600E-dependent tumor xenograft models, orally dosed PLX4720 causes significant tumor growth delays, including tumor regressions, without evidence of toxicity. The work described here represents the entire discovery process, from initial identification through structural and biological studies in animal models to a promising therapeutic for testing in cancer patients bearing B-RafV600E-driven tumors.
121764664
The DIRC prototype for the WASA experiment at COSY
The implementation of a DIRC (Detector or Internally Reflected Cherenkov light) was planned for the WASA-at-COSY experiment, located at the Forschungszentrum Julich and is a major project for the future PANDA experiment at FAIR. In order to study the components and the behavior of the detector under experimental conditions, a large scale demonstrator made of acrylic glass was built and tested at the external proton beam of the COSY accelerator. The main properties of the components, especially of the newly developed front end electronics and the results of the first tests are presented.
15336878
Hot subdwarfs from the stable Roche lobe overflow channel
Context. Hot subdwarfs are core-helium-burning stars with extremely thin envelopes. We discuss the formation and evolution of hot subdwarfs formed through the stable Roche lobe overflow (RLOF) channel of intermediate-mass binaries, although their formation channels are various. Aims. In this study, we concentrate on the formation and evolution of hot subdwarfs binaries through the stable RLOF channel of intermediate-mass binaries. We aim at setting out the properties of hot subdwarfs and their progenitors, so that we can understand the formation and evolution of hot subdwarfs. Methods. Employing Eggleton's stellar evolution code, we have computed conservative and nonconservative population I binary evolution sequences. The initial mass of the primary ranges from 2.2 to 6.3 M(circle dot), spaced by approximately 0.1 in log M, the initial mass ratio q(i) = M(1)/M(2) is between 1.1 and 4.5, and the Roche lobe overflow begins at the main sequence, the Hertzsprung gap and the first giant branch. In nonconservative binary evolution, we assume that 50 percent of the mass lost from the primary leaves the system, carrying away the specific angular momentum of the primary, and the remaining mass is accreted on to the secondary during the RLOF. Also, we have studied the distributions of the mass and orbital periods of hot subdwarfs using the population synthesis approach. Results. We have obtained the ranges of the initial parameters of progenitor binaries and the properties of hot subdwarfs through the stable RLOF channel of intermediate-mass binaries, e. g. mass, envelope mass and age of hot subdwarfs. We have found that hot subdwarfs could be formed through stable Roche lobe overflow at the main sequence and Hertzsprung gap. We have also found that some subdwarf B or OB stars have anomalously high mass (similar to 1 M(circle dot)) with a thick envelope (similar to 0.07 M(circle dot)-similar to 0.16) in our models. By comparing our theoretical results with observations on the hot subdwarfs in open clusters, we suggest that more hot subdwarfs in binary systems might be found in open clusters in the future.
122970197
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha(s)
Multijet production rates in neutral current deep inelastic scattering (DIS) have been measured in the range of exchanged boson virtualities 10<Q2<5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential multijet cross sections are presented as functions of jet transverse energy , pseudorapidity and Q2 with and . Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant αs(MZ), determined from the ratio of the trijet to dijet cross sections, is .
122921203
Search for the neutral Higgs bosons of the minimal supersymmetric standard model from Z0 decays
We present the results from a search for the light neutral scalar Higgs boson h° and the pseudoscalar Higgs boson A° of the minimal super-symmetric standard model. The analysis is based on a data sample corresponding to 71 000 hadronic Z° decays recorded with the L3 detector at LEP. No evidence for the existence of the neutral Higgs bosons h° and A° has been found. The region of h° and A° masses up to 41.5 GeV is excluded at 95% confidence level.
118348723
Some aspects of QGP phase in a hQCD model
A bstractWe continue to study the holographic QCD (hQCD) model, proposed in a previous paper, in an Einstein-Maxwell-Dilaton (EMD) system. In this paper we discuss some aspects of quark gluon plasma (QGP) in the hQCD model, such as drag force, jet quenching parameter and screening length. The results turn out to be consistent with those as expected in QCD qualitatively. By calculating free energy of the background black hole solution, we find that there exists a phase transition between small black hole and large black hole when chemical potential μ is less than the critical one μc, and the phase transition is absent when chemical potential is beyond the critical one.
12639048
Towards complete phase diagrams of a holographic p-wave superconductor model
A bstractWe study in detail the phase structure of a holographic p-wave superconductor model in a five dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. To construct complete phase diagrams of the model, we consider both the soliton and black hole backgrounds. In both two cases, there exist second order, first order and zeroth order phase transitions, and the so-called “retrograde condensation” also happens. In particular, in the soliton case with the mass of the vector field being beyond a certain critical value, we find a series of phase transitions happen such as “insulator/superconductor/insulator/superconductor”, as the chemical potential continuously increases. We construct complete phase diagrams in terms of temperature and chemical potential and find some new phase boundaries.
17626348
Some Calculations for Cold Fusion Superheavy Elements
The Q value and optimal exciting energy of the hypothetical superheavy nuclei in cold fusion reaction are calculated with relativistic mean field model and semiemperical shell model mass equation(SSME) and the validity of the two models is tested. The fusion barriers are also calculated with two different models and reasonable results are obtained. The calculations can give useful references for the experiments in the superheavy nuclei synthesized in cold fusion reactions. The formation of compound nuclei by cold fusion reaction is one of the outstanding problem of low-energy nuclear reactions. Such processes play a key role in the production of superheavy elements(SHEs)[1–4]. Experiments or intensive preparatory work are in progress at the laboratories such as Dubna, Berkeley, RIKEN and GANIL etc. Theoretical support of these very expensive experiments is vital in the choice of fusing nuclei and their collision energy, and for the estimation of the cross sections and identification of evaporation residues. The quantum mechanical fragmentation theory(QMFT) which was developed by Gupta et al. to describe the synthesis of new and superheavy elements gives us a method for selecting an optimum cold target-projectile combination. Cold compound systems were considered to be formed for all those target+projectile combinations that lie at the bottom of the potential energy minima[5–7]. On the basis of the QMFT, recently, Gupta lists all the possible target+projectile combinations, referring to minima in PES, in particular, the use of radioactive nuclear beams and targets. There are several important physical values such as Q values, the heights of the fusion barrier Bfu and the optimal excitation energies E ∗ for the cold fusion reaction. The aims of this paper are to find some proper methods to predict the ground-state Q values, the heights of the fusion barrier Bfu and the optimal excitation energies E ∗ for the cold fusion reaction. Then, following the work of Gupta et al. in Ref. we calculate Q, Bfu and E ∗ for the possible target+projectile combinations to give some significative references for the future experiments. Supported by National Natural Science Foundation of China (10275037) and Specialized Research Fund for the Doctoral Program of Higher Education of China (20010055012) E-mail: zhongxianhui@mail.nankai.edu.cn E-mail: lilei@nankai.edu.cn E-mail: ningpz@nankai.edu.cn
119198410
Loop quantum cosmology with higher order holonomy corrections
With a well-motivated extension of higher order holonomy corrections, the quantum theory of loop quantum cosmology (LQC) for the $k=0$ Friedmann-Robertson-Walker model (with a free massless scalar) is rigorously formulated. The analytical investigation reveals that, regardless of the order of holonomy corrections and for any arbitrary states, the matter density remains finite, bounded from above by an upper bound, which equals the critical density obtained at the level of heuristic effective dynamics. Particularly, with all orders of corrections included, the dynamical evolution is shown to follow the bouncing scenario in which two Wheeler-DeWitt solutions (expanding and contracting) are bridged together through the quantum bounce. These observations provide further evidence that the quantum bounce is essentially a consequence of the intrinsic discreteness of LQC and LQC is fundamentally different from the WDW theory. Meanwhile, the possibility is also explored so that the higher order holonomy corrections can be interpreted as a result of admitting generic $SU(2)$ representations for the Hamiltonian constraint operators.
45431684
Time machines constructed from anti–de Sitter space
In this paper time machines are constructed from anti-de Sitter space. One is constructed by identifying points related via boost transformations in the covering space of anti-de Sitter space and it is shown that this Misner-like anti-de Sitter space is just the Lorentzian section of the complex space constructed by Li, Xu, and Liu in 1993. The others are constructed by gluing an anti-de Sitter space to a de Sitter space, which could describe an anti-de Sitter phase bubble living in a de Sitter phase universe. Self-consistent vacua for a massless conformally coupled scalar field are found for these time machines, whose renormalized stress-energy tensors are finite and solve the semi-classical Einstein equations. The extensions to electromagnetic fields and massless neutrinos are discussed. It is argued that, in order to make the results consistent with Euclidean quantization, a new renormalization procedure for quantum fields in Misner-type spaces (Misner space, Misner-like de Sitter space, and Misner-like anti-de Sitter space) is required. Such a "self-consistent" renormalization procedure is proposed. With this renormalization procedure, self-consistent vacua exist for massless conformally coupling scalar fields, electromagnetic fields, and massless neutrinos in these Misner-type spaces.