The Chiral Phase Transition in Dissipative Dynamics

Numerical simulations of the chiral phase transition in the (3+1)dimensional O(4)-model are presented. The evolutions of the chiral field follow purely dissipative dynamics, starting from random chirally symmetric initial configurations down to the true vacuum with spontaneously broken symmetry. The model stabilizes topological textures which are formed together with domains of disoriented chiral condensate (DCC) during the roll-down phase. The classically evolving field acts as source for the emission of pions and $\sigma$ mesons. The exponents of power laws for the growth of angular correlations and for emission rates are extracted. Fluctuations in the abundance ratios for neutral and charged pions are compared with those for uncorrelated sources as potential signature for the chiral phase transition after heavy-ion collisions. It is found that the presence of stabilizing textures (baryons and antibaryons) prevents sufficiently rapid growth of DCC-domain size, so observability of anomalous tails in the abundance ratios is unlikely. However, the transient formation of growing DCC domains causes sizable broadening of the distributions as compared to the statistical widths of generic sources.Comment: 28 pages, 8 figure

PHYLO-ASP: Phylogenetic Systematics with Answer Set Programming

This note summarizes the use of Answer Set Programming to solve various computational problems to infer phylogenetic trees and phylogenetic networks, and discusses its applicability and effectiveness on some real taxa

Charge and Isospin Fluctuations in High Energy pp-Collisions

Charge and isospin event-by-event fluctuations in high-energy pp-collisions are predicted within the Unitary Eikonal Model, in particular the fluctuation patterns of the ratios of charged-to-charged and neutral-to-charged pions. These fluctuations are found to be sensitive to the presence of unstable resonances, such as $\rho$ and $\omega$ mesons. We predict that the charge-fluctuation observable $D_{UEM}$ should be restricted to the interval $8/3\le D_{UEM}\le 4$ depending on the $\rho /\pi$ production ratio. Also, the isospin fluctuations of the DCC-type of the ratio of neutral-to-charged pions are suppressed if pions are produced together with $\rho$ mesons.Comment: Latex, 5 pages, no figures. To appear in the proceedings of 9th Adriatic Meeting, Dubrovnik, Croatia, 4 - 14 September 2003. Added reference into reference no.

Unifying Parsimonious Tree Reconciliation

Evolution is a process that is influenced by various environmental factors, e.g. the interactions between different species, genes, and biogeographical properties. Hence, it is interesting to study the combined evolutionary history of multiple species, their genes, and the environment they live in. A common approach to address this research problem is to describe each individual evolution as a phylogenetic tree and construct a tree reconciliation which is parsimonious with respect to a given event model. Unfortunately, most of the previous approaches are designed only either for host-parasite systems, for gene tree/species tree reconciliation, or biogeography. Hence, a method is desirable, which addresses the general problem of mapping phylogenetic trees and covering all varieties of coevolving systems, including e.g., predator-prey and symbiotic relationships. To overcome this gap, we introduce a generalized cophylogenetic event model considering the combinatorial complete set of local coevolutionary events. We give a dynamic programming based heuristic for solving the maximum parsimony reconciliation problem in time O(n^2), for two phylogenies each with at most n leaves. Furthermore, we present an exact branch-and-bound algorithm which uses the results from the dynamic programming heuristic for discarding partial reconciliations. The approach has been implemented as a Java application which is freely available from http://pacosy.informatik.uni-leipzig.de/coresym.Comment: Peer-reviewed and presented as part of the 13th Workshop on Algorithms in Bioinformatics (WABI2013

Exploring leadership in multi-sectoral partnerships

This article explores some critical aspects of leadership in the context of multi-sectoral partnerships. It focuses on leadership in practice and asks the question, `How do managers experience and perceive leadership in such partnerships?' The study contributes to the debate on whether leadership in a multi-sectoral partnership context differs from that within a single organization. It is based on the accounts of practising managers working in complex partnerships. The article highlights a number of leadership challenges faced by those working in multi-sectoral partnerships. Partnership practitioners were clear that leadership in partnerships was more complex than in single organizations. However, it was more difficult for them to agree a consensus on the essential nature of leadership in partnership. We suggest that a first-, second- and third-person approach might be a way of better interpreting leadership in the context of partnerships

A Study of the S=1/2 Alternating Chain using Multiprecision Methods

In this paper we present results for the ground state and low-lying excitations of the $S=1/2$ alternating Heisenberg antiferromagnetic chain. Our more conventional techniques include perturbation theory about the dimer limit and numerical diagonalization of systems of up to 28 spins. A novel application of multiple precision numerical diagonalization allows us to determine analytical perturbation series to high order; the results found using this approach include ninth-order perturbation series for the ground state energy and one magnon gap, which were previously known only to third order. We also give the fifth-order dispersion relation and third-order exclusive neutron scattering structure factor for one-magnon modes and numerical and analytical binding energies of S=0 and S=1 two-magnon bound states.Comment: 16 pages, 9 figures. for submission to Phys.Rev.B. PICT files of figs available at http://csep2.phy.ornl.gov/theory_group/people/barnes/barnes.htm

A Complete Theory of Grand Unification in Five Dimensions

A fully realistic unified theory is constructed, with SU(5) gauge symmetry and supersymmetry both broken by boundary conditions in a fifth dimension. Despite the local explicit breaking of SU(5) at a boundary of the dimension, the large size of the extra dimension allows precise predictions for gauge coupling unification, alpha_s(M_Z) = 0.118 \pm 0.003, and for Yukawa coupling unification, m_b(M_Z) = 3.3 \pm 0.2 GeV. A complete understanding of the MSSM Higgs sector is given; with explanations for why the Higgs triplets are heavy, why the Higgs doublets are protected from a large tree-level mass, and why the mu and B parameters are naturally generated to be of order the SUSY breaking scale. All sources of d=4,5 proton decay are forbidden, while a new origin for d=6 proton decay is found to be important. Several aspects of flavor follow from an essentially unique choice of matter location in the fifth dimension: only the third generation has an SU(5) mass relation, and the lighter two generations have small mixings with the heaviest generation. The entire superpartner spectrum is predicted in terms of only two free parameters. The squark and slepton masses are determined by their location in the fifth dimension, allowing a significant experimental test of the detailed structure of the extra dimension. Lepton flavor violation is found to be generically large in higher dimensional unified theories with high mediation scales of SUSY breaking. In our theory this forces a common location for all three neutrinos, predicting large neutrino mixing angles. Rates for mu -> e gamma, mu -> e e e, mu -> e conversion and tau -> mu gamma are larger in our theory than in conventional 4D supersymmetric GUTs. Proposed experiments probing mu -> e transitions will probe the entire interesting parameter space of our theory.Comment: 51 pages, late