Date: Fri, 26 Feb 16 01:20:34 GMT Subject: hep-lat daily 3 new + 1 crosses received by eprepget ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Send any comments regarding submissions directly to submitter. ------------------------------------------------------------------------------ Archives at http://arxiv.org/ To unsubscribe, e-mail To: hep-lat@arXiv.org, Subject: cancel ------------------------------------------------------------------------------ received by eprepget from Wed 24 Feb 16 21:00:00 GMT to Thu 25 Feb 16 21:00:00 GMT ------------------------------------------------------------------------------ \\ arXiv:1602.07688 Date: Wed, 24 Feb 2016 21:00:01 GMT (173kb) Title: Remarks on the pion-nucleon sigma-term Authors: Martin Hoferichter, Jacobo Ruiz de Elvira, Bastian Kubis, Ulf-G. Mei{\ss}ner Categories: hep-lat hep-ph nucl-th Comments: 5 pages, 2 figures Report-no: INT-PUB-16-006 \\ The pion-nucleon $\sigma$-term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about $3\sigma$ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms. \\ ( http://arxiv.org/abs/1602.07688 , 173kb) ------------------------------------------------------------------------------ \\ arXiv:1602.07737 Date: Wed, 24 Feb 2016 22:28:00 GMT (535kb,D) Title: Controlling Excited-State Contamination in Nucleon Matrix Elements Authors: Boram Yoon, Rajan Gupta, Tanmoy Bhattacharya, Michael Engelhardt, Jeremy Green, B\'alint Jo\'o, Huey-Wen Lin, John Negele, Kostas Orginos, Andrew Pochinsky, David Richards, Sergey Syritsyn, Frank Winter Categories: hep-lat Report-no: LA-UR-16-20524 \\ We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a 2+1 flavor ensemble with lattices of size $32^3 \times 64$ generated using the rational hybrid Monte Carlo algorithm at $a=0.081$~fm and with $M_\pi=312$~MeV. The statistical precision of the data is improved using the all-mode-averaging method. We compare two methods for reducing excited-state contamination: a variational analysis and a two-state fit to data at multiple values of the source-sink separation $t_{\rm sep}$. We show that both methods can be tuned to significantly reduce excited-state contamination and discuss their relative advantages and cost-effectiveness. A detailed analysis of the size of source smearing used in the calculation of quark propagators and the range of values of $t_{\rm sep}$ needed to demonstrate convergence of the isovector charges of the nucleon to the $t_{\rm sep} \to \infty $ estimates is presented. \\ ( http://arxiv.org/abs/1602.07737 , 535kb) ------------------------------------------------------------------------------ \\ arXiv:1602.07797 Date: Thu, 25 Feb 2016 05:09:34 GMT (1670kb) Title: $\Lambda_c-N$ interaction from lattice QCD Authors: Takaya Miyamoto, for HAL QCD Collaboration Categories: hep-lat hep-ph nucl-th Comments: 7 pages, 3 figures, and 3 tables, Proceedings for the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe, Japan Report-no: YITP-16-19 \\ We investigate the s-wave $\Lambda_c-N$ interaction for spin singlet systems($^1S_0$) using the HAL QCD method. In our lattice QCD simulations, we employ gauge configurations generated by the PACS-CS Collaboration at $a = 0.0907(13)$ fm on a $32^3 \times 64$ lattice ($La = 2.902(42)$ fm). We employ two ensembles, one at $m_\pi = 700(1)$ MeV and the other at $m_\pi = 570(1)$ MeV to study the quark mass dependence of the $\Lambda_c-N$ interactions. We calculate a $^1S_0$ central potential not only for the $\Lambda_c-N$ system but also for $\Lambda-N$ system to understand the role of heavy charm quarks in $\Lambda_c-N$ system. We find repulsion at short distance and attraction at mid-range for both the $\Lambda_c-N$ and the $\Lambda-N$ potentials. The short range repulsion of the $\Lambda_c-N$ potential is smaller than that of the $\Lambda-N$ potential, and the attraction of the $\Lambda_c-N$ potential is small compared with the $\Lambda-N$ potential. The phase shift and scattering length calculated with these potentials show that there exist no bound state for both the $\Lambda_c-N$ and $\Lambda-N$ systems for $m_{\pi} > 570$ MeV. \\ ( http://arxiv.org/abs/1602.07797 , 1670kb) %-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%- ------------------------------------------------------------------------------ \\ arXiv:1602.08036 (*cross-listing*) Date: Thu, 25 Feb 2016 19:09:31 GMT (547kb) Title: Thermodynamics of the $d$=3+1 Quantum XY Model Authors: Christoph P. Hofmann Categories: cond-mat.str-el hep-lat hep-ph Comments: 34 pages, 9 figures \\ Within effective field theory we explore the properties of the $d$=3+1 quantum XY model at low temperatures and in weak magnetic or staggered fields. For this parameter regime only few results appear to be known, and furthermore are restricted to one-loop order. In the present study we systematically analyze the thermodynamics of the $d$=3+1 quantum XY model up to three-loop order. In the low-temperature expansion of the free energy density, the free Bose gas term of order $T^4$ receives corrections of order $T^6$ and $T^8$. The discussion also includes the pressure, (staggered) magnetization and susceptibility. In particular, we show how these quantities are influenced by the spin-wave interaction. We then compare our findings with those for the quantum XY model in $d$=2+1. \\ ( http://arxiv.org/abs/1602.08036 , 547kb) %%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%% %%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%--- For subscribe options to combined physics archives, e-mail To: physics@arxiv.org, Subject: subscribe ----------------------------------------------------------------------------- For help on viewing and making submissions, see http://arxiv.org/help/