17561372
The static quark potential in 2+1 flavour Domain Wall QCD from QCDOC
We report our present status of on-going project on the measurement of the static quark potential in 2+1 flavour domain wall QCD with various improved gauge actions and couplings. Lattice spacing determined from Sommer scale on these ensembles are from 1.6 GeV to 2.0 GeV for $16^3 \times 32$ lattice with fifth dimension size 8. We also examine size of discretization error from scaling of a pair of dimensionless quantities, $(r_0 m_\pi)^2$ and $r_0 m_\rho$, and found small scaling violation.
119245910
Development of lattice QCD tool kit on cell broadband engine processor
Research Institute for Information Science and Education, Hiroshima University,Higashi-Hiroshima, Hiroshima, 739-8521, JapanE-mail: nakamura@riise.hiroshima-u.ac.jpWe report an implementation of a code for SU(3) matrix multiplication on Cell/B.E., which is apart of our project, Lattice Tool Kit on Cell/B.E.. On QS20, the speed of the matrix multiplicationon SPE in single precision is 227GFLOPS and it becomes 20GFLOPS together with data transferfrom main memory by DNA transfer, which is 4.6% of the hardware peak speed (460GFLOPS),and is 7.4% of the theoretical peak speed of this calculation (268.77GFLOPS). We brieﬂy describeour tuning procedure.The XXVII International Symposium on Lattice Field Theory - LAT2009July 26-31 2009Peking University, Beijing, China
118599955
Dynamical QCD simulation with theta terms
The theta term that breaks the Strong CP symmetry is introduced in the two flavors of dynamical QCD simulation. theta is analytically continued to a pure imaginary number to make the probability of Monte Carlo positive. The Neutron's Electric Dipole Moment (NEDM) is measured on the ensemble under a uniform and week electric field. Other applications of theta terms are also discussed.
14999048
Seiberg-Witten transforms of noncommutative solitons
We evaluate the Seiberg-Witten map for solitons and instantons in noncommutative gauge theories in various dimensions. We show that solitons constructed using the projection operators have delta-function supports when expressed in the commutative variables. This gives a precise identification of the moduli of these solutions as locations of branes. On the other hand, an instanton solution in four dimensions allows deformation away from the projection operator construction. We evaluate the Seiberg-Witten transform of the U(2) instanton and show that it has a finite size determined by the noncommutative scale and by the deformation parameter ρ. For large ρ, the profile of the D0-brane density of the instanton agrees surprisingly well with that of the Belavin-Polyakov-Schwarz-Tyupkin (BPST) instanton on commutative space.
17625514
Dynamical Decay of Brane-Antibrane and Dielectric Brane
Using D-brane effective field theories, we study dynamical decay of unstable brane systems : (i) a parallel brane-antibrane pair with separation l and (ii) a dielectric brane. In particular we give explicitly the decay width of these unstable systems, and describe how the decay proceeds after the tunnel effect. The decay (i) is analysed by the use of a tachyon effective action on the Dp-Dpbar. A pair annihilation starts by nucleation of a bubble of a tachyon domain wall which represents a throat connecting these branes, and the tunneling decay width is found to be proportional to exp(-l^{p+1} T_{Dp}). We study also the decay leaving topological defects corresponding to lower-dimensional branes, which may be relevant for recent inflationary braneworld scenario. As for the decay (ii), first we observe that Dp-branes generically ``curl up'' in a nontrivial RR field strength. Using this viewpoint, we compute the decay width of the dielectric D2-branes by constructing relevant Euclidean bounce solutions in the shape of a funnel. We also give new solutions in doughnut shape which are involved with nucleation of dielectric branes from nothing.
6555533
Time evolution viaS-branes
Using S(pacelike)-branes defined through rolling tachyon solutions, we show how the dynamical formation of D(irichlet)-branes and strings in tachyon condensation can be understood. Specifically we present solutions of S-brane actions illustrating the classical confinement of electric and magnetic flux into fundamental strings and D-branes. The role of S-branes in string theory is further clarified and their RR charges are discussed. In addition, by examining ``boosted'' S-branes, we find what appears to be a surprising dual S-brane description of strings and D-branes, which also indicates that the critical electric field can be considered as a self-dual point in string theory. We also introduce new tachyonic S-branes as Euclidean counterparts to non-BPS branes.