Lattice calculation of the strangeness and electromagnetic nucleon form factors

We report on recent lattice QCD calculations of the strangeness magnetic moment of the nucleon and the nucleon electromagnetic form factors, when we allow the electromagnetic current to connect to quark loops as well as to the valence quarks. Our result for the strangeness magnetic moment is G_M^s(0)=-0.36+/-0.20. The sea contributions from the u and d quarks are about 80% larger. However, they cancel to a large extent due to their electric charges, resulting in a smaller net sea contribution of -0.097+/-0.037 mu_N to the nucleon magnetic moment. As far as the neutron to proton magnetic moment ratio is concerned, this sea contribution tends to cancel out the cloud-quark effect from the Z-graphs and results in a ratio of -0.68+/-0.04 which is close to the SU(6) relation and the experiment. The strangeness Sachs electric mean-square radius _E is found to be small and negative and the total sea contributes substantially to the neutron electric form factor.Comment: LATTICE98(matrixelement); 3 pages, no figures, to appear in Lattice '98 proceeding

One Belt — One Road Initiative: A Window of Opportunity for Russia’s Western Border Regions

In recent years, global geo-economic transformations have been considerably affected by the development of the People’s Republic of China, its reviving leadership and ambitions, and its increasing efforts to reformat and integrate the Eurasian space. The One Belt — One Road Initiative is a manifesto and a tool to advance China’s long-term geostrategic interests that spread to the bordering states and regions and to the prospects of their socioeconomic development. The initiative encompasses transportation and logistics, production and investment, finances, research and technology, humanitarian affairs, and foreign policy. In this article, we will highlight the key geoeconomic and geopolitical aspects of the One Belt — One Road initiative implementation, based on the Chinese and Russian studies. Another goal is to weigh up the risks and benefits associated with the extension of the project to Russian territories. Special attention is paid to Russia’s western borderlands — 17 regions that account for 8.6 % of the country’s territory, 17.4 % of the total GRP, and 20.8% of the national population. We analyse the factors in effect — including geopolitical ones, as well as current trends in the development of Russia’s western borderlands. It is shown that the inclusion into the Chinese Eurasian integration initiatives creates additional incentives for a positive re-evaluation of the Russian space as a whole and holds special relevance for Russia’s western borderlands. We analyse the possibility of including Russia’s Baltic regions — the infrastructural and economic island of the Kaliningrad exclave among them — into the One Belt — One Road Initiative

Nonperturbative renormalisation of composite operators with overlap quarks

We compute non-perturbatively the renormalisation constants of composite operators on a $16^3 \times 32$ lattice with lattice spacing $a$ = 0.093 fm for the overlap fermion action by using the regularisation independent (RI) scheme. The quenched gauge configurations are generated by tadpole improved plaquette plus rectangle action. We test the perturbative continuum relation $Z_A = Z_V$ and $Z_S=Z_P$ and find that they agree well above $\mu$ = 1.6 GeV. We also perform a Renormalisation Group analysis at the next-to-next-to-leading order and convert the renormalisation constants to the $\bar{MS}$ scheme.Comment: Talk given at LHP2003, Cairns, Australi

Holographic dark energy in a universe with spatial curvature and massive neutrinos: a full Markov Chain Monte Carlo exploration

In this paper, we report the results of constraining the holographic dark energy model with spatial curvature and massive neutrinos, based on a Markov Chain Monte Carlo global fit technique. The cosmic observational data include the full WMAP 7-yr temperature and polarization data, the type Ia supernova data from Union2.1 sample, the baryon acoustic oscillation data from SDSS DR7 and WiggleZ Dark Energy Survey, and the latest measurements of $H_0$ from HST. To deal with the perturbations of dark energy, we adopt the parameterized post-Friedmann method. We find that, for the simplest holographic dark energy model without spatial curvature and massive neutrinos, the phenomenological parameter $c<1$ at more than $4\sigma$ confidence level. The inclusion of spatial curvature enlarges the error bars and leads to $c<1$ only in about $2.5\sigma$ range; in contrast, the inclusion of massive neutrinos does not have significant influence on $c$. We also find that, for the holographic dark energy model with spatial curvature but without massive neutrinos, the $3\sigma$ error bars of the current fractional curvature density $\Omega_{k0}$ are still in order of $10^{-2}$; for the model with massive neutrinos but without spatial curvature, the $2\sigma$ upper bound of the total mass of neutrinos is $\sum m_{\nu} < 0.48$ eV. Moreover, there exists clear degeneracy between spatial curvature and massive neutrinos in the holographic dark energy model, which enlarges the upper bound of $\sum m_{\nu}$ by more than 2 times. In addition, we demonstrate that, making use of the full WMAP data can give better constraints on the holographic dark energy model, compared with the case using the WMAP ``distance priors''.Comment: 21 pages, 10 figures; major revision; new figures and discussions added; accepted by JCA

The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed neutrinos

We implement the seesaw mechanism in the 3-3-1 model with right-handed neutrinos. This is accomplished by the introduction of a scalar sextet into the model and the spontaneous violation of the lepton number. We identify the Majoron as a singlet under $SU_L(2)\otimes U_Y(1)$ symmetry, which makes it safe under the current bounds imposed by electroweak data. The main result of this work is that the seesaw mechanism works already at TeV scale with the outcome that the right-handed neutrino masses lie in the electroweak scale, in the range from MeV to tens of GeV. This window provides a great opportunity to test their appearance at current detectors, though when we contrast our results with some previous analysis concerning detection sensitivity at LHC, we conclude that further work is needed in order to validate this search.Comment: about 13 pages, no figure

B→ϕπB\to \phi \pi and B0→ϕϕB^0 \to \phi\phi in the Standard Model and new bounds on R parity violation

We study the pure penguin decays $B \to \phi\pi$ and $B^0 \to \phi\phi$. Using QCD factorization, we find ${\cal B}(B^\pm \to\phi\pi^{\pm} )=2.0^{+0.3}_{-0.1}\times 10^{-8}$. For the pure penguin annihilation process $B^0 \to \phi\phi$, analyzed here for the first time, ${\cal B}(B^0 \to\phi\phi)=2.1^{+1.6}_{-0.3}\times 10^{-9}$. The smallness of these decays in the Standard Model makes them sensitive probes for new physics. From the upper limit of $B\to \phi\pi$,we find constraints on R parity violating couplings, $| \lambda{''}_{i23}\lambda{''}_{i21}|<6\times10^{-5}$, $| \lambda'_{i23}\lambda'_{i21}|<4\times10^{-4}$ and $| \lambda'_{i32}\lambda'_{i12}|<4\times10^{-4}$ for $i=1,2,3$. Our new bounds on $|\lambda{''}_{i23}\lambda{''}_{i21}|$ are one order of magnitude stronger than before. Within the available upper bounds for $| \lambda{''}_{i23}\lambda{''}_{i21}|$, $|\lambda'_{i23}\lambda'_{i21}|$ and $|\lambda'_{i32}\lambda'_{i12}|$, we find that ${\cal B}(B\to\phi\phi)$ could be enhanced to $10^{-8}\sim 10^{-7}$. Experimental searches for these decays are strongly urged.Comment: 5 pages, 3 figures embede

Scalar Potential Without Cubic Term in 3-3-1 Models Without Exotic Electric Charges

A detailed study of the criteria for stability of the scalar potential, and the proper electroweak symmetry breaking pattern in some 3-3-1 models without exotic electric charges is presented. In this paper we concentrate in a scalar sector with three Higgs scalar triplets, with a potential that does not include the cubic term, due to the presence of a discrete symmetry. For the analysis we use, and improve, a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. Our main result is to show the consistency of those 3-3-1 models without exotic electric charges.Comment: 19 page

Pairing symmetry and long range pair potential in a weak coupling theory of superconductivity

We study the superconducting phase with two component order parameter scenario, such as, $d_{x^2-y^2} + e^{i\theta}s_{\alpha}$, where $\alpha = xy, x^2+y^2$. We show, that in absence of orthorhombocity, the usual $d_{x^2-y^2}$ does not mix with usual $s_{x^2+y^2}$ symmetry gap in an anisotropic band structure. But the $s_{xy}$ symmetry does mix with the usual d-wave for $\theta =0$. The d-wave symmetry with higher harmonics present in it also mixes with higher order extended $s$ wave symmetry. The required pair potential to obtain higher anisotropic $d_{x^2-y^2}$ and extended s-wave symmetries, is derived by considering longer ranged two-body attractive potential in the spirit of tight binding lattice. We demonstrate that the dominant pairing symmetry changes drastically from $d$ to $s$ like as the attractive pair potential is obtained from longer ranged interaction. More specifically, a typical length scale of interaction $\xi$, which could be even/odd multiples of lattice spacing leads to predominant $s/d$ wave symmetry. The role of long range interaction on pairing symmetry has further been emphasized by studying the typical interplay in the temperature dependencies of these higher order $d$ and $s$ wave pairing symmetries.Comment: Revtex 8 pages, 7 figures embeded in the text, To appear in PR

Spin Injection and Detection in Magnetic Nanostructures

We study theoretically the spin transport in a nonmagnetic metal connected to ferromagnetic injector and detector electrodes. We derive a general expression for the spin accumulation signal which covers from the metallic to the tunneling regime. This enables us to discuss recent controversy on spin injection and detection experiments. Extending the result to a superconducting device, we find that the spin accumulation signal is strongly enhanced by opening of the superconducting gap since a gapped superconductor is a low carrier system for spin transport but not for charge. The enhancement is also expected in semiconductor devices.Comment: 4 pages, 3 figure

A Lattice Study of the Magnetic Moment and the Spin Structure of the Nucleon

Using an approach free from momentum extrapolation, we calculate the nucleon magnetic moment and the fraction of the nucleon spin carried by the quark angular momentum in the quenched lattice QCD approximation. Quarks with three values of lattice masses, 210, 124 and 80 MeV, are formulated on the lattice using the standard Wilson approach. At every mass, 100 gluon configurations on 16^3 x 32 lattice with \beta=6.0 are used for statistical averaging. The results are compared with the previous calculations with momentum extrapolation. The contribution of the disconnected diagrams is studied at the largest quark mass using noise theory technique.Comment: 14 pages, 3 figures, Talk given at Lattice2001, Berlin, German