Reheating Closed String Inflation

Protecting the inflationary potential from quantum corrections typically requires symmetries that constrain the form of couplings of the inflaton to other sectors. We will explore how these restrictions affect reheating in models with UV completions. In particular, we look at how reheating occurs when inflation is governed by closed strings, using N-flation as an example. We find that coupling the inflaton preferentially to the Standard Model is difficult, and hidden sectors are typically reheated. Observational constraints are only met by a fraction of the models. In some working models, relativistic relics in the hidden sector provide dark matter candidates with masses that range from keV to PeV, with lighter masses being preferred.Comment: 17 pages, v2: fixed typos and added refs, v3: fixed typos, added refs and title chang

The anyon model: an example inspired by string theory

We investigate the enlarged class of open finite strings in $(2+1)D$ space-time. The new dynamical system related to this class is constructed and quantized here. As the result, the energy spectrum of the model is defined by a simple formula ${\sf S} = \alpha_n{\sf E} + c_n$; the spin ${\sf S}$ is an arbitrary number here but the constants $\alpha_n$ and $c_n$ are eigenvalues for certain spectral problems in fermionic Fock space ${\bf H}_\psi$ constructed for the free 2D fermionic field.Comment: 19 pages; to be published in Int. Journ. of Mod. Phys.

Generic Syzygy Schemes

For a finite dimensional vector space G we define the k-th generic syzygy scheme Gensyz_k(G) by explicit equations. We show that the syzygy scheme Syz(f) of any syzygy in the linear strand of a projective variety X which is cut out by quadrics is a cone over a linear section of a corresponding generic syzygy scheme. We also give a geometric description of Gensyz_k(G) for k=0,1,2. In particular Gensyz_2(G) is the union of a Pl"ucker embedded Grassmannian and a linear space. From this we deduce that every smooth, non-degenerate projective curve C which is cut out by quadrics and has a p-th linear syzygy of rank p+3 admits a rank 2 vector bundle E with det E = O_C(1) and h^0(E) at least p+4.Comment: 12 Pages. This paper is a completely rewritten version of the first part of math.AG/0108078. It also contains several new result

Lifting Grobner bases from the exterior algebra

In the article "Non-commutative Grobner bases for commutative algebras", Eisenbud-Peeva-Sturmfels proved a number of results regarding Grobner bases and initial ideals of those ideals in the free associative algebra which contain the commutator ideal. We prove similar results for ideals which contains the anti-commutator ideal (the defining ideal of the exterior algebra). We define one notion of generic initial ideals in the free assoicative algebra, and show that gin's of ideals containing the commutator ideal, or the anti-commutator ideal, are finitely generated.Comment: 6 pages, LaTeX2

Generalized Green-Schwarz mechanism in F theory

We derive the anomaly 8-form of 6-dimensional gauge theories arising in F theory compactifications on elliptic Calabi-Yau threefolds. The result allows to determine the matter content of certain such theories in terms of intersection numbers on the base of elliptic fibration. We also discuss gauge theories on 7-branes with double point singularities on the worldvolume. Applications to Type II compactifications on Hirzebruch surfaces and $P^2$ are outlined.Comment: 11 pages, harvmac. Normalization of (tr R^2)^2 term correcte

Approach to rapid mission design and planning

Methods and techniques are described for implementation in automated computer systems to assess parametric data, capabilities, requirements and constraints for planning earth orbit missions. Mission planning and design procedures are defined using two types of typical missions as examples. These missions were the high energy Astronomical Observatory Satellite missions, and Small Applications Technology Satellite missions

Magnetic Properties of Pd_(0.996)Mn_(0.004) Films for High Resolution Thermometry

We have previously reported on the temperature and magnetic field dependence of the magnetic susceptibility of thin Pd_(1−x)Mn_x alloy films. Extensive new measurements on sputtered films show that a commercial quality sputtering process produces a film with the same dependence of Curie temperature on x as previously reported for bulk samples of the same material. These measurements and parameters from the Renormalization Group theory for a Heisenberg ferromagnet, yield an estimate for T_c of 1.16 ± 0.01 K when x − 0.004, consistent with previously reported bulk result

Financial Expertise as an Arms Race

We propose a model in which firms involved in trading securities overinvest in financial expertise. Intermediaries or traders in the model meet and bargain over a financial asset. As in the bargaining model in Dang (2008), counterparties endogenously decide whether to acquire information, and improve their bargaining positions, even though the information creates adverse selection. We add to this setting the concept of "financial expertise" as resources invested to lower the cost of later acquiring information about the value of the asset being traded. These investments are made before the parties know about their role in the bargaining game, as proposer or responder, buyer or seller. A prisoner's dilemma arises because investments to lower information acquisition costs improve bargaining outcomes given the other party's information costs, even though the information has no social benefit. These investments lead to breakdowns in trade, or liquidity crises, in response to random but infrequent increases in asset volatilityFinancial services;over-the-counter markets;financial crisis