121130487
The Ising and anisotropy phase transitions of the periodic XY model in a transverse field
It is found that, for a periodic XY chain, the competition between periodicity and anisotropy gives rise to more than one phase-transition point at some parameter region. In this paper, the phase diagram of a period-two XY model in a transverse field is discussed. Two phase transitions, the Ising and anisotropy transitions, driven by the anisotropy parameter ?, are studied by singularities of the order parameters, the ground-state energy and the quantum entanglement. These two transitions are of second order and their traits are discussed.
36756339
A MORE PRECISE EXTRACTION OF |Vcb| IN HQEFT OF QCD
The more precise extraction for the CKM matrix element |Vcb| in the heavy quark effective field theory (HQEFT) of QCD is studied from both exclusive and inclusive semileptonic B decays. The values of relevant nonperturbative parameters up to order $1/m^2_Q$ are estimated consistently in HQEFT of QCD. Using the most recent experimental data for B decay rates, |Vcb| is updated to be |Vcb|=0.0395±0.0011expt±0.0019theor from B→D*lν decay and |Vcb|=0.0434±0.0041expt±0.0020theor from B→Dlν decay as well as |Vcb|=0.0394±0.0010expt±0.0014theor from inclusive B→Xclν decay.
123052577
Unparticle effects on neutrinoless and neutrino double beta decay
The neutrinoless and neutrinos double beta decays are investigated in an effective theory where a scalar unparticle is introduced. We calculate the contributions of a virtual unparticle to the rates of 0ν2β and 2ν2β decays. The unparticle effect is negligibly small when the scaling dimension d of unparticle lies in the region 1.1-1.9. But it can be relatively large when d approaches to 1 or 2. We also study the neutrinoless double beta decay with a real unparticle in the final state which cannot be distinguished from 2ν2β decay in experiment. We consider the unparticle effect on extracting the neutrino mass parameter mββ from experimental data and find that it can be relatively large when d takes certain values.
117848077
Could $Z_{b}(10610)$ be a $B^{*}\bar{B}$ molecular state?
Assuming the newly observed structure $Z_{b}(10610)$ as a bottomonium-like molecular state $B^{*}\bar{B}$, we calculate its mass in the framework of QCD sum rules. The numerical result is $10.54\pm0.22 GeV$ for $B^{*}\bar{B}$, which coincide with the mass of $Z_{b}(10610)$. This consolidates the statement made by Belle Collaboration that the $Z_{b}(10610)$ resonance could be a $B^{*}\bar{B}$ molecular state.
9148058
Challenge to the a theorem in six dimensions.
The possibility of a strong a theorem in six dimensions is examined in multiflavor ϕ^{3} theory. Contrary to the case in two and four dimensions, we find that, in perturbation theory, the relevant quantity a[over ˜] increases monotonically along flows away from the trivial fixed point. a[over ˜] is a natural extension of the coefficient a of the Euler term in the trace anomaly, and it arises in any even spacetime dimension from an analysis based on Weyl consistency conditions. We also obtain the anomalous dimensions and beta functions of multiflavor ϕ^{3} theory to two loops. Our results suggest that some new intuition about the a theorem is in order.
118041104
Correction to the Running of Gauge Couplings out of Extra Dimensional Gravity
We study the gravitational correction to the gauge couplings in the extra dimension model where the gravity propagates in the (4+n)-dimensional bulk. We show by explicit calculation in the background field method that the one-loop correction coming from graviton Kaluza-Klein states is nontrivial and tends to make the theory anti-asymptotically free. For the theory characterized with asymptotic freedom, the correction will induce a nontrivial UV-stable fixed point. This may lead to an interesting possibility that the non-abelian gauge coupling constants $g_2$ and $g_3$ in the SM and that of the gravity $g_{\kappa}$ unify at the fixed point in the limit of high energy scale.
117276480
The Sun's Origin, Composition and Source of Energy
Composition: Diffusion enriches lighter elements and the lighter isotopes of each element at the solar surface. When corrected for mass fractionation, the most abundant nuclide that accreted on the Sun was shown to be Fe, the decay product of doubly-magic Ni; the next most abundant nuclide is the doublymagic O. These nuclides were recently observed in the ash of SN 1987A. The most abundant elements Fe, Ni, O, Si, S, Mg, and Ca are the seven, even-Z elements that Harkins found to comprise 99% of ordinary meteorites. The least abundant elements Li, Be and B have loosely bound nucleons, confirming a link between abundance and nuclear structure hidden beneath the Sun’s H-rich surface, with one conspicuous and important exception an excess of protons.