Counting surface branched covers

To a branched cover f between orientable surfaces one can associate a certain branch datum D(f), that encodes the combinatorics of the cover. This D(f) satisfies a compatibility condition called the Riemann-Hurwitz relation. The old but still partly unsolved Hurwitz problem asks whether for a given abstract compatible branch datum D there exists a branched cover f such that D(f)=D. One can actually refine this problem and ask how many these f's exist, but one must of course decide what restrictions one puts on such f's, and choose an equivalence relation up to which one regards them. And it turns out that quite a few natural choices are possible. In this short note we carefully analyze all these choices and show that the number of actually distinct ones is only three. To see that these three choices are indeed different we employ Grothendieck's dessins d'enfant.Comment: 15 pages, 1 figur

Current Algebras and Symmetries in Bootstrap Theory

In the first paper of this series we showed how, in the bootstrap theory, the currents associated with the hadrons could be determined from a set of self-consistency conditions. In the present paper we show that these "self-consistent" currents satisfy a current algebra. The proof is accomplished without recourse to any approximate model It includes the interesting case of nonconserved currents. The convergence of sum rules derived from current algebras is investigated in detail, and shown to be most rapid when no "nonbootstrap" terms are present. Using these convergence properties, we discuss how and when current algebras can give rise to hadron symmetries

An Economic Theory of Foreign Interventions and Regime Change

I construct a theory of foreign interventions in which the preferences of the foreign country over alternative local groups are determined by each group's international economic ties. In equilibrium, the foreign country supports the group with which it has the strongest ties, since this is most influenceable from the outside. However this is counterweighted by the tendency of the domestic political system to favour the least influenceable group. I allow for a non-economic dimension of policy (geopolitics), and study how the saliency of this dimension may play in favor of the incumbent group. My results help interpret the economic rationale for many Western interventions in developing countries in the 20th century, and the role of economic nationalism in motivating the struggle for regime change. Furthermore, they help explain why the Cold War strengthened the West's preference for specific local groups. I provide detailed historical evidence in favor of my arguments.regime change, foreign interventions, economic power, economic nationalism, Cold War, Latin America

Anti-proton production and annihilation in nuclear collisions at 15-A/GeV

We present a calculation of antiproton yields in Si+Al and Si+Au collisions at 14.5A GeV in the framework of the relativistic quantum molecular dynamics approach (RQMD). Multistep processes lead to the formation of high-mass flux tubes. Their decay dominates the initial antibaryon yield. However, the subsequent annihilation in the surrounding baryon-rich matter suppresses the antiproton yield considerably: Two-thirds of all antibaryons are annihilated even for the light Si+Al system. Comparisons with preliminary data of the E802 experiment support this analysis

Spartan Daily, April 30, 1974

Volume 62, Issue 43https://scholarworks.sjsu.edu/spartandaily/5867/thumbnail.jp

Access to financing, rents, and organization of the firm

This paper provides a theory for the choice of an organizational structure by the headquarters of a unitary structure concerned about overload. The headquarters can avoid overload by delegating operational decisions to divisions, i.e., moving the firm to a multidivisional structure. We show that, under moral hazard, these divisions receive rents for incentive purposes, and that the multidivisional structure is able to invest more. Thus, there is a trade-off between increasing investment and paying rents. We also show that this trade-off applies to situations where firms consider engaging in acquisitions and joint ventures, or where entrepreneurs consider resorting to venture capitalists.Unitary-form; Multidivisional-form; Agency rents; Credit rationing

The Cowl - v.26 - n.17 - Apr 22, 1964

The Cowl - student newspaper of Providence College. Volume 26, Number 17 - April 22, 1964. 8 pages

Deceit: A flexible distributed file system

Deceit, a distributed file system (DFS) being developed at Cornell, focuses on flexible file semantics in relation to efficiency, scalability, and reliability. Deceit servers are interchangeable and collectively provide the illusion of a single, large server machine to any clients of the Deceit service. Non-volatile replicas of each file are stored on a subset of the file servers. The user is able to set parameters on a file to achieve different levels of availability, performance, and one-copy serializability. Deceit also supports a file version control mechanism. In contrast with many recent DFS efforts, Deceit can behave like a plain Sun Network File System (NFS) server and can be used by any NFS client without modifying any client software. The current Deceit prototype uses the ISIS Distributed Programming Environment for all communication and process group management, an approach that reduces system complexity and increases system robustness