Fri·Sep 16, 2005Friday·September 16, 2005

1. 01*

   Gauge invariance in a Z_2 hamiltonian lattice gauge theory

   Takanori Sugihara (RIKEN BNL)🇺🇸

   We propose an efficient variational method for $Z_2$ lattice gauge theory based on the matrix product ansatz. The method is applied to ladder and square lattices. The Gauss law needs to be imposed on quantum states to guarantee gauge invariance when one studies gauge theory in hamiltonian formalism. On the ladder lattice, we identify gauge invariant low-lying states by evaluating expectation values of the Gauss law operator after numerical diagonalization of the gauge hamiltonian. On the square lattice, the second order phase transition is well reproduced.

   hep-latcond-mat.str-elPoS(2006)·1 citation
2. 02*

   Lattice QCD - A guide for people who want results

   Christine Davies🇬🇧

   Lattice QCD was invented thirty years ago but only in the last few years has it finally fulfilled its promise as a precision tool for calculations in hadron physics. This review will cover the fundamentals of discretising QCD onto a space-time lattice and how to reduce the errors associated with the discretisation. This 'improvement' is the key that has made the enormous computational task of a lattice QCD calculation tractable and enabled us to reach the recent milestone of precision calculations of simple 'gold-plated' hadron masses. Accurate decay matrix elements, such as those for leptonic and semileptonic decays of heavy mesons needed by the B factory experimental programme, are now within sight. I will describe what goes into such calculations and what the future prospects and limitations are.

   hep-lat16 citations
3. 03*

   Casimir Scaling of domain wall tensions in the deconfined phase of D=3+1 SU(N) gauge theories

   Francis Bursa🇬🇧 · Michael Teper🇬🇧

   We perform lattice calculations of the spatial 't Hooft k-string tensions in the deconfined phase of SU(N) gauge theories for N=2,3,4,6. These equal (up to a factor of T) the surface tensions of the domain walls between the corresponding (Euclidean) deconfined phases. For T much larger than T_c our results match on to the known perturbative result, which exhibits Casimir Scaling, being proportional to k(N-k). At lower T the coupling becomes stronger and, not surprisingly, our calculations show large deviations from the perturbative T-dependence. Despite this we find that the behaviour proportional to k(N-k) persists very accurately down to temperatures very close to T_c. Thus the Casimir Scaling of the 't Hooft tension appears to be a `universal' feature that is more general than its origin in the low order high-T perturbative calculation. We observe the `wetting' of these k-walls at T around T_c and the (almost inevitable) `perfect wetting' of the k=N/2 domain wall. Our calculations show that as T tends to T_c the magnitude of the spatial `t Hooft string tension decreases rapidly.

   hep-latPoS(2006)·0 citations
4. 04*

   Critical thermodynamics of two-dimensional N-vector cubic model in the five-loop approximation

   P. Calabrese🇮🇹 · E.V. Orlov🇷🇺 · D.V. Pakhnin🇷🇺 · A.I. Sokolov🇷🇺

   The critical behavior of the two-dimensional N-vector cubic model is studied within the field-theoretical renormalization-group (RG) approach. The beta-functions and critical exponents are calculated in the five-loop approximation, RG series obtained are resummed using Pade-Borel-Leroy and conformal mapping techniques. It is found that for N = 2 the continuous line of fixed points is well reproduced by the resummed RG series and an account for the five-loop terms makes the lines of zeros of both beta-functions closer to each another. For N > 2 the five-loop contributions are shown to shift the cubic fixed point, given by the four-loop approximation, towards the Ising fixed point. This confirms the idea that the existence of the cubic fixed point in two dimensions under N > 2 is an artifact of the perturbative analysis. In the case N = 0 the results obtained are compatible with the conclusion that the impure critical behavior is controlled by the Ising fixed point.

   ↳ cond-mat.stat-mechhep-lathep-phhep-thCondensed Matter Phys.(2005)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.