Local thermal equilibrium and ideal gas Stephani universes

The Stephani universes that can be interpreted as an ideal gas evolving in local thermal equilibrium are determined. Five classes of thermodynamic schemes are admissible, which give rise to five classes of regular models and three classes of singular models. No Stephani universes exist representing an exact solution to a classical ideal gas (one for which the internal energy is proportional to the temperature). But some Stephani universes may approximate a classical ideal gas at first order in the temperature: all of them are obtained. Finally, some features about the physical behavior of the models are pointed out.Comment: 20 page

The Case For Consistency: What Justifies The Maintenance Of A Top International Hotel Reputation?

This case addresses the issues encountered when an international hotel chain develops the reputation for being a “top” hotel.  The case examines the situation of visitors who pay, by American standards, the premium price for a stay at this chain’s Acapulco resort only to encounter inconsistent and, at times, questionable service.  Discussion questions and teaching notes are included

Corporate Higher Education: Models And Examples

Corporate education has become a major influence in higher education today.  The goal of this initiative is to explore the forms that higher corporate education takes.  Among the most prevalent are: specifically designed university programs, partnership programs between a company and a university, and corporation designed programs created and offered to meet the specific needs of educating their employees in training matters and providing development within the corporate structure.  While there is no set formula for fashioning a successful program the myriad variations provide an opportunity to explore the pros and cons of each model.  An example of a successful corporate higher education program is explored

Mentoring: Who And How

This paper examines the concept of mentoring, defined here as a process where one individual, the mentor, passes on knowledge, experience and advice to another individual, the mentee, in trust and confidence. This process is initiated by a corporation whose purpose it is to recruit, retain and grow talented people in their organization. A survey of the history of the process is reviewed. The benefits and issues of acquiring a mentor and advancing are also covered. Four interviews are reported, the authors feel that this overview of mentoring has many applications and need not be confined to the business community

Rainich theory for type D aligned Einstein-Maxwell solutions

The original Rainich theory for the non-null Einstein-Maxwell solutions consists of a set of algebraic conditions and the Rainich (differential) equation. We show here that the subclass of type D aligned solutions can be characterized just by algebraic restrictions.Comment: 12 pages; v2: appendix with notatio

Real null coframes in general relativity and GPS type coordinates

Based on work of Derrick, Coll, and Morales, we define a `symmetric' null coframe with {\it four real null covectors}. We show that this coframe is closely related to the GPS type coordinates recently introduced by Rovelli.Comment: Latex script, 9 pages, 4 figures; references added to work of Derrick, Coll, and Morales, 1 new figur

A physical application of Kerr-Schild groups

The present work deals with the search of useful physical applications of some generalized groups of metric transformations. We put forward different proposals and focus our attention on the implementation of one of them. Particularly, the results show how one can control very efficiently the kind of spacetimes related by a Generalized Kerr-Schild (GKS) Ansatz through Kerr-Schild groups. Finally a preliminar study regarding other generalized groups of metric transformations is undertaken which is aimed at giving some hints in new Ans\"atze to finding useful solutions to Einstein's equations.Comment: 18 page

On the Weyl transverse frames in type I spacetimes

We apply a covariant and generic procedure to obtain explicit expressions of the transverse frames that a type I spacetime admits in terms of an arbitrary initial frame. We also present a simple and general algorithm to obtain the Weyl scalars $\Psi_2^T$, $\Psi_0^T$ and $\Psi_4^T$ associated with these transverse frames. In both cases it is only necessary to choose a particular root of a cubic expression.Comment: 12 pages, submitted to Gen. Rel. Grav. (6-3-2004

On the existence of Killing vector fields

In covariant metric theories of coupled gravity-matter systems the necessary and sufficient conditions ensuring the existence of a Killing vector field are investigated. It is shown that the symmetries of initial data sets are preserved by the evolution of hyperbolic systems.Comment: 9 pages, no figure, to appear in Class. Quant. Gra