Massimo Bernaschi

The deconfining phase transition in lattice gauge SU(3)

Abstract By using a source method and improved measuring techniques, we study the decay of the Polyakov loop in SU(3) lattice gauge theory at finite temperature. Our aim is to measure the correlation length of the system in the neighbourhood of the critical point. We work with lattices of size up to 162×64×4. We found that the maximum correlation length is only bounded by the spatial dimension of the lattice. This result is the one expected in a second order phase transition and appears to be incompatible with the presence of the strong first order transition claimed in the literature.

Scaling in lattice QCD: Glueball masses and string tension

Abstract We study the scaling behaviour of lattice quantum chromodynamics by comparing the β dependence of the string tension and the 0 ++ glueball mass. We use a source method at β =5.7, β =5.9 and β =6.1, on lattices from 9 3 · 24 to 16 3 · 32. Assuming a string tension of about (420 MeV) 2 , the lattice spacing ranges from 0.16 to 0.08 fm. In order to separate finite volume from scaling violation effects we have compared data from lattices having approximately the same overall physical size at the different values of β. We find deviations from scaling to be very small.

Renormalization group study of the three state three dimensional Potts model

Abstract We make a renormalisation group study with the finite size real space renormalization group (FSRSRG) technique of the order of the transition in the three dimensional three state Potts model with nearest neighbor and next to nearest neighbour couplings. Our results provide evidence that the order-disorder transition from a high temperature phase to a low temperature phase is discontinuous not only in the region characterized by both couplings being positive but also when the next to nearest coupling is appreciably antiferromagnetic. In both cases the correlation length exponent, previously not known, converges to the value expected for a first order first transition but only for large volumes, especially in the antiferromagnetic case.

PVMe: an enhanced implementation of PVM for the IBM 9076 SP2

We present PVMe, IBMs AIX implementation of the widely used PVM message passing programming model. The focus is on the version for the IBM 9076 SP2. The basic PVMe design is described along with the results obtained running some significant applications on this platform.

Complex zeros of the partition function for compact lattice QED

Abstract A general method for the study of the complex zeros of the partition function for lattice theories with fermions is applied to compact U(1) with dynamical fermions. In particular, we obtain the zeros of the partition function on the complex quark mass plane. On a small 4 4 lattice we study in a systematic way the dependence of the zeros on the theorys parameters, on lattice artefacts and on the various tuning parameters we have implemented.

Efficient message passing on UNIX shared memory multiprocessors

Abstract We describe a single-copy mechanism which enables an efficient message passing among UNIX processes on shared memory multiprocessors. A special version of PVMe , IBMs AIX implementation of the PVM message passing programming model, has been built based on this approach. Some preliminary results here reported show the clear advantage of the single-copy with respect to more conventional schemes.

The critical temperature in renormalization group studies of first order phase transitions

Abstract We perform a renormalization group study of the first order phase transition of the two dimensional Z(10) Potts model for which an ambiguous determination of the critical temperature was claimed. Allowing the system to flip between the two different phases in the large-volume limit near the critical point one can determine the critical temperature without ambiguity.

Efficient Message Passing on Shared Memory Multiprocessors

We have described a non-conventional scheme for the message passing on SMP systems. It may represent a possible solution to the performance issues of existing or new PVM applications on such systems and it has the important feature of being completely transparent to the users which are not required to change their codes. We like to stress that the same mechanism could be used for other message passing libraries (e.g. MPI) and that, although with some effort, we expect it to be portable to other SMP platforms as well.

Development and results of PVMe on the IBM 9076 SP1

Abstract We present PVMe, IBM′s AIX implementation of the widely used PVM message passing programming model. The focus is on the version for the IBM 9076 SP1. The PVMe design is thoroughly described along with the results obtained running some significant applications on this platform. A summary of the experiences of using PVM as the base for the implementation of other communication libraries (namely, PARMACS) concludes the work.

OpenCAPWAP: an open-source CAPWAP implementation for management and QoS support

The Control And Provisioning of Wireless Access Points (CAPWAP) protocol is under development within the IETF to enable an Access Controller (AC) to manage a collection of Wireless Termination Points (WTPs). CAPWAP aims at simplifying the deployment and control of large scale, possibly heterogeneous, wireless networks. We present the first open source implementation of the CAPWAP protocol along with early experimental results aiming at the assessment of its reliability and performances. The paper ends describing applications of the CAPWAP protocol to QoS scenarios and discussing benefits and technical issues.