Phase diagram of the restricted solid-on-solid model coupled to the Ising model

We study the phase transitions of a restricted solid-on-solid model coupled to an Ising model, which can be derived from the coupled XY-Ising model. There are two kinds of phase transition lines. One is a Ising transition line and the other is surface roughening transition line. The latter is a KT transition line from the viewpoint of the XY model. Using a microcanonical Monte Carlo technique, we obtain a very accurate two dimensional phase diagram. The two transition lines are separate in all the parameter space we study. This result is strong evidence that the fully frustrated XY model orders by two separate transitions and that roughening and reconstruction transitions of crystal surfaces occur separately.Comment: 17 pages, source RevTeX file and 8 PS figures are tarred and compressed via uufile

CP Violation in Heavy MSSM Higgs Scenarios

We introduce and explore new heavy Higgs scenarios in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation, which have important phenomenological implications that may be testable at the LHC. For soft supersymmetry-breaking scales M_S above a few TeV and a charged Higgs boson mass M_H+ above a few hundred GeV, new physics effects including those from explicit CP violation decouple from the light Higgs boson sector. However, such effects can significantly alter the phenomenology of the heavy Higgs bosons while still being consistent with constraints from low-energy observables, for instance electric dipole moments. To consider scenarios with a charged Higgs boson much heavier than the Standard Model (SM) particles but much lighter than the supersymmetric particles, we revisit previous calculations of the MSSM Higgs sector. We compute the Higgs boson masses in the presence of CP violating phases, implementing improved matching and renormalization group (RG) effects, as well as two-loop RG effects from the effective two-Higgs Doublet Model (2HDM) scale M_H+ to the scale M_S. We illustrate the possibility of non-decoupling CP-violating effects in the heavy Higgs sector using new benchmark scenarios named CPX4LHC.Comment: 39 pages, 17 figures, LaTeX, typos correcte

Phase transitions in the one-dimensional frustrated quantum XY model and Josephson-junction ladders

A one-dimensional quantum version of the frustrated XY (planar rotor) model is considered which can be physically realized as a ladder of Josephson-junctions at half a flux quantum per plaquette. This system undergoes a superconductor to insulator transition at zero temperature as a function of charging energy. The critical behavior is studied using a Monte Carlo transfer matrix applied to the path-integral representation of the model and a finite-size-scaling analysis of data on small system sizes. Depending on the ratio between the interchain and intrachain couplings the system can have single or double transitions which is consistent with the prediction that its critical behavior should be described by the two-dimensional classical XY-Ising model.Comment: 13 pages, Revtex, J. Appl. Phys. (to appear), Inpe-las-00

Sandpiles on multiplex networks

We introduce the sandpile model on multiplex networks with more than one type of edge and investigate its scaling and dynamical behaviors. We find that the introduction of multiplexity does not alter the scaling behavior of avalanche dynamics; the system is critical with an asymptotic power-law avalanche size distribution with an exponent $\tau = 3/2$ on duplex random networks. The detailed cascade dynamics, however, is affected by the multiplex coupling. For example, higher-degree nodes such as hubs in scale-free networks fail more often in the multiplex dynamics than in the simplex network counterpart in which different types of edges are simply aggregated. Our results suggest that multiplex modeling would be necessary in order to gain a better understanding of cascading failure phenomena of real-world multiplex complex systems, such as the global economic crisis.Comment: 7 pages, 7 figure