Gauge Quintessence

We discuss a new model of quintessence in which the quintessence field is identified with the extra-component of a gauge field in a compactified five-dimensional theory. We show that the extremely tiny energy scale $\sim (3\times 10^{-3} eV)^4$ needed to account for the present acceleration of the Universe can be naturally explained in terms of high energy scales such as the scale of Grand Unification.Comment: 3 page

Evidence that the T cell antigen receptor may not be involved in cytotoxicity mediated by gamma/delta and alpha/beta thymic cell lines.

After culture in IL-2, thymocytes expressing either TCR-alpha/beta or -gamma/delta acquired the ability to lyse hematopoietic and solid tumor cell targets without deliberate immunization or apparent restriction by the MHC. Moreover, TCR-alpha/beta- and TCR-gamma/delta-bearing thymic cell lines demonstrated an essentially identical spectrum of cytolysis against several tumor cell targets. Cytotoxicity was not inhibited by antibodies against CD3 or CD2 and modulation of the CD3/TCR complex also failed to affect cytotoxicity. Thus, non-MHC-restricted cytotoxicity can be mediated by thymocytes with either TCR-alpha/beta or TCR-gamma/delta, but the TCR may not be responsible for target recognition

Buyer power in U.K. food retailing: a 'first-pass' test

Habtu Weldegebriel, University of Warwick Abstract The potential existence of buyer power in U.K. food retailing has attracted the scrutiny of the U.K.'s anti-trust authorities, culminating in the second of two comprehensive regulatory inquiries in recent years. Such inquiries are authoritative but correspondingly time-consuming and costly. Moreover, detection of buyer power has been dogged by the paucity of reliable evidence of its existence. In this paper, we present a simple theoretical model of oligopsony which delivers quasi-reduced form retailer-producer pricing equations with which the null of perfect competition can be tested using readily available market data. Using a cointegrated vector autoregression, we find empirical results that show the null of perfect competition can be rejected in seven of the nine food products investigated. Though not conclusive on the existence of buyer power, the proposed test offers a means via which the behaviour of the retail-producer price spread is consistent with it. At the very least, it can corroborate the concerns of the anti-trust authorities as to whether buyer power is potentially one source of concern

Market Power in UK Food Retailing: Theory and Evidence from Seven Product Groups

Establishing the presence of market power in food chains has become an increasingly pertinent line of enquiry given the trend towards increasing concentration that has been observed in many parts of the world. This paper presents a theoretical model of price transmission in vertically related markets under imperfect competition. The model delivers a quasi-reduced form representation that is empirically tractable using readily available market data to test for the presence of market power. In particular, we show that the hypothesis of perfect competition can be rejected if shocks to the demand and supply function are significant and correctly signed in price transmission equations. Using a cointegrated vector autoregression, we find empirical results that are consistent with downstream market power in six out of seven food products investigated, supporting both the findings of the UK competition authority's recent investigation in to supermarkets and renewed calls for further scrutiny of supermarket behaviour by the UK's Office of Trading.imperfect competition, Cointegrated VARs, UK food industry, Marketing, D4, L81,