Interacting Bosons at Finite Temperature: How Bogolubov Visited a Black Hole and Came Home Again

The structure of the thermal equilibrium state of a weakly interacting Bose gas is of current interest. We calculate the density matrix of that state in two ways. The most effective method, in terms of yielding a simple, explicit answer, is to construct a generating function within the traditional framework of quantum statistical mechanics. The alternative method, arguably more interesting, is to construct the thermal state as a vector state in an artificial system with twice as many degrees of freedom. It is well known that this construction has an actual physical realization in the quantum thermodynamics of black holes, where the added degrees of freedom correspond to the second sheet of the Kruskal manifold and the thermal vector state is a state of the Unruh or the Hartle-Hawking type. What is unusual about the present work is that the Bogolubov transformation used to construct the thermal state combines in a rather symmetrical way with Bogolubov's original transformation of the same form, used to implement the interaction of the nonideal gas in linear approximation. In addition to providing a density matrix, the method makes it possible to calculate efficiently certain expectation values directly in terms of the thermal vector state of the doubled system.Comment: 25 pages, LaTeX. To appear in a special issue of Foundations of Physics in honor of Jacob Bekenstei

Expression and Purification of Z Protein from Junín Virus

Arenaviridae comprises 23 recognized virus species with a bipartite ssRNA genome and an ambisense coding strategy. The virions are enveloped and include nonequimolar amounts of each genomic RNA species, designated L and S, coding for four ORFs (N, GPC, L, and Z). The arenavirus Junín (JUNV) is the etiological agent of Argentine Hemorrhagic Fever, an acute disease with high mortality rate. It has been proposed that Z is the functional counterpart of the matrix proteins found in other negative-stranded enveloped RNA viruses. Here we report the optimized expression of a synthetic gene of Z protein, using three expression systems (two bacterial and a baculoviral one). One of these recombinant proteins was used to generate antibodies. A bioinformatic analysis was made where Z was subdivided into three domains. The data presented contributes methodologies for Z recombinant production and provides the basis for the development of new experiments to test its function

Market Structure after Horizontal Mergers: Evidence from the Banking Industry

Antitrust policy, Competition, Market structure, Banking industry mergers, G21, G28, G34, L11, L13,

Explaining M&A Success in European Banks

"We study 98 large M&As of European bidding banks from 1985 to 2000 in order to investigate drivers of excess returns to the shareholders of the targets, the bidders, and to the combined entity of the bidder and the target. Our findings show that many of 13 drivers identified mostly from prior, US-focused research have significant explanatory power, indicating that the stock market reaction to M&A announcements of European bidding banks can be at least partly forecast. Our results are largely consistent with the US-experience and confirm the preference of stock markets for focused transactions and against diversification. Moreover, we find that less active bidders create more value than more active/experienced bidders. This stands in contrast to some US research and may indicate that managers of frequent European bidding banks may be motivated by other objectives than creating shareholder value." Copyright Blackwell Publishers Ltd, 2004.

Bank Governance and Acquisition Performance

Given the pivotal role of banks in modern economies, the worldwide phenomenon of a high level of bank M&A activity and the consensus view in empirical studies that bank mergers destroy value for acquiring bank shareholders, it is highly surprising that the influence of corporate governance on the outcomes of bank acquisitions has received very little academic scrutiny. The recent wave of consolidation in the financial services industry, with its generally unfavourable wealth implications for the shareholders of acquiring institutions, points to the impact of poor bank governance structures. Moreover, the banking sector warrants a separate agency analysis because it is unusual, if not unique, in terms of the opaque nature of many of its main activities and in terms of the pervasive role of regulation in the industry. Both of these attributes may weaken well-established monitoring mechanisms as safeguards of shareholder interests. Copyright (c) 2007 The Authors; Journal compilation (c) 2007 Blackwell Publishing Ltd.