3,252 research outputs found
Bond-Propagation Algorithm for Thermodynamic Functions in General 2D Ising Models
Recently, we developed and implemented the bond propagation algorithm for
calculating the partition function and correlation functions of random bond
Ising models in two dimensions. The algorithm is the fastest available for
calculating these quantities near the percolation threshold. In this paper, we
show how to extend the bond propagation algorithm to directly calculate
thermodynamic functions by applying the algorithm to derivatives of the
partition function, and we derive explicit expressions for this transformation.
We also discuss variations of the original bond propagation procedure within
the larger context of Y-Delta-Y-reducibility and discuss the relation of this
class of algorithm to other algorithms developed for Ising systems. We conclude
with a discussion on the outlook for applying similar algorithms to other
models.Comment: 12 pages, 10 figures; submitte
Photonic mode density effects on single-molecule fluorescence blinking
We investigated the influence of the photonic mode density (PMD) on the
triplet dynamics of individual chromophores on a dielectric interface by
comparing their response in the presence and absence of a nearby gold film.
Lifetimes of the excited singlet state were evaluated in ordet to measure
directly the PMD at the molecules position. Triplet state lifetimes were
simultaneously determined by statistical analysis of the detection time of the
fluorescence photons. The observed singlet decay rates are in agreement with
the predicted PMD for molecules with different orientations. The triplet decay
rate is modified in a fashion correlated to the singlet decay rate. These
results show that PMD engineering can lead to an important suppression of the
fluorescence, introducing a novel aspect of the physical mechanism to enhance
fluorescence intensity in PMD-enhancing systems such as plasmonic devices
Modelling the influence of RKIP on the ERK signalling pathway using the stochastic process algebra PEPA
This paper examines the influence of the Raf Kinase Inhibitor Protein (RKIP) on the Extracellular signal Regulated Kinase (ERK) signalling pathway [5] through modelling in a Markovian process algebra, PEPA [11]. Two models of the system are presented, a reagent-centric view and a pathway-centric view. The models capture functionality at the level of subpathway, rather than at a molecular level. Each model affords a different perspective of the pathway and analysis. We demonstrate the two models to be formally equivalent using the timing-aware bisimulation defined over PEPA models and discuss the biological significance
Entropic long range order in a 3D spin glass model
We uncover a new kind of entropic long range order in finite dimensional spin
glasses. We study the link-diluted version of the Edwards-Anderson spin glass
model with bimodal couplings (J=+/-1) on a 3D lattice. By using exact reduction
algorithms, we prove that there exists a region of the phase diagram (at zero
temperature and link density low enough), where spins are long range
correlated, even if the ground states energy stiffness is null. In other words,
in this region twisting the boundary conditions cost no energy, but spins are
long range correlated by means of pure entropic effects.Comment: 15 pages, 6 figures. v3: added a phase diagram for ferromagnetically
biased coupling
Issues on Orientifolds: On the brane construction of gauge theories with SO(2n) global symmetry
We discuss issues related to orientifolds and the brane realization for gauge
theories with orthogonal and symplectic groups. We specifically discuss the
case of theories with (hidden) global SO(2n) symmetry, from three to six
dimensions. We analyze mirror symmetry for three dimensional N=4 gauge
theories, Brane Box Models and six-dimensional gauge theories. We also discuss
the issue of T-duality for D_n space-time singularities. Stuck D branes on ON^0
planes play an interesting role.Comment: 38 pages, 23 figures, uses bibtex and (provided) utphys.bs
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