Split Attractor Flow in N=2 Minimally Coupled Supergravity

We classify the stability region, marginal stability walls (MS) and split attractor flows for two-center extremal black holes in four-dimensional N=2 supergravity minimally coupled to n vector multiplets. It is found that two-center (continuous) charge orbits, classified by four duality invariants, either support a stability region ending on a MS wall or on an anti-marginal stability (AMS) wall, but not both. Therefore, the scalar manifold never contains both walls. Moreover, the BPS mass of the black hole composite (in its stability region) never vanishes in the scalar manifold. For these reasons, the "bound state transformation walls" phenomenon does not necessarily occur in these theories. The entropy of the flow trees also satisfies an inequality which forbids "entropy enigma" decays in these models. Finally, the non-BPS case, due to the existence of a "fake" superpotential satisfying a triangle inequality, can be treated as well, and it can be shown to exhibit a split attractor flow dynamics which, at least in the n=1 case, is analogous to the BPS one.Comment: 1+29 pages, 2 figures; v2: minor changes, especially in Sects. 1 and 2; Sect. 6 changed. To appear on NP

Black holes, first-order flow equations and geodesics on symmetric spaces

For both extremal and non-extremal spherically symmetric black holes in theories with massless scalars and vectors coupled to gravity, we derive a general form of first-order gradient flow equations, equivalent to the equations of motion. For theories that have a symmetric moduli space after a dimensional reduction over the timelike direction, we discuss the condition for such a gradient flow to exist. This note reviews the results of arXiv:0810.1528 [hep-th].Comment: 6 pages, contribution to the proceedings of the 4th RTN Workshop 'Constituents, Fundamental Forces and Symmetries of the Universe', Varna, 11-17 September 2008; v2: a reference adde

Community engagement at Roger Williams University: community service - service learning - civic engagement

Service to the local community has become a part of the college tradition as more campuses incorporate service into their curricular and co-curricular cultures. Roger Williams University parallels this trend. Service has evolved from “a nice thing to do” to an important element in our academic and co-curricular culture. We have outgrown the blanket term “service” and can place campus-wide service activities in three distinct categories: community service, service learning, and civic engagement. While based on the common goal of promoting active citizenship, each category contains distinct experiences with distinct learning outcomes

Web Services: A Process Algebra Approach

It is now well-admitted that formal methods are helpful for many issues raised in the Web service area. In this paper we present a framework for the design and verification of WSs using process algebras and their tools. We define a two-way mapping between abstract specifications written using these calculi and executable Web services written in BPEL4WS. Several choices are available: design and correct errors in BPEL4WS, using process algebra verification tools, or design and correct in process algebra and automatically obtaining the corresponding BPEL4WS code. The approaches can be combined. Process algebra are not useful only for temporal logic verification: we remark the use of simulation/bisimulation both for verification and for the hierarchical refinement design method. It is worth noting that our approach allows the use of any process algebra depending on the needs of the user at different levels (expressiveness, existence of reasoning tools, user expertise)

The Failed Critique of Personal Accounts

Even though President Bush's Commission to Strengthen Social Security has yet to produce a specific proposal to establish a personal account option for Social Security, opponents of the idea have already put forward a barrage of objections and criticisms. Those criticisms generally reflect fundamental misconceptions of and confusion about Social Security's current problems. Social Security is facing a financial crisis as early as 2016. The Social Security Trust Fund will not delay the onset of Social Security's problems. The critics are equally mistaken about individual accounts. Individual accounts do not involve simply switching investments from bonds to stocks. There would be no reduction in survivors' or disability benefits. Although the mix of benefits would change, workers would have higher, not lower, overall benefits under individual accounts. Finally, benefits under the current system are not guaranteed, but workers would have a property right to the funds in their individual accounts

Recent developments in non-perturbative quantum field theory

We report on recent advances in the understanding of non-perturbative phenomena in the quantum theory of fields and strings.Comment: 6 pages, latex, uses stwol.sty; Plenary talk given at International Conference on High Energy Physics (ICHEP), Warsaw, July 199

Bertotti-Robinson Geometry and Supersymmetry

The role of Bertotti-Robinson geometry in the attractor mechanism of extremal black holes is described for the case of N = 2 supersymmetry. Its implication for a model-independent derivation of the Bekenstein-Hawking entropy formula is discussed.Comment: 13 pages, figures, uses procsla,epsf,epsfig; Talk given at the 12th Italian Conference on General Relativity and Gravitational Physics, Rome, September 199