Supersymmetric Theories on a Non Simply Connected Space-Time

We study the Wess-Zumino theory on ${\bf R}^3 \times S^1$ where a spatial coordinate is compactified. We show that when the bosonic and fermionic fields satisfy the same boundary condition, the theory does not develop a vacuum energy or tadpoles. We work out the two point functions at one loop and show that their forms are consistent with the nonrenormalization theorem. However, the two point functions are nonanalytic and we discuss the structure of this nonanalyticity.Comment: 10 pages, TEX file, figures upon request from author

Banks and Real Estate Prices

The willingness of banks to provide funding for real estate purchases depends on the creditworthiness of their borrowers. Beside other factors, the creditworthiness of borrowers depends on the development of real estate prices. Real estate prices, in turn, depend on the demand for homes which is influenced by the willingness of banks to provide funding for real estate purchases. In this paper I develop a theoretical model which describes and explains this circular relationship. Using this model, I show how different kinds of expectation formations can lead to fluctuations of real estate prices. Furthermore, I show that banks make above average profits in the upswing phase of the real estate cycle but suffer high losses when the market turns.Credit Cycle, Real Estate Prices, Bubbles

On the Ward Identities at Finite Temperature

We show both in 1+1 and 3+1 dimensions that, contrary to the recent suggestions, the contribution of the fermion loop to the polarization tensor is manifestly transverse at finite temperature. Some subtleties associated with the Ward identities at finite temperature are also pointed out.Comment: 12 pages, UR-1361, ER40685-81

Asymptotic behavior of the ground state energy of a Fermionic Fr\"ohlich multipolaron in the strong coupling limit

In this article, we investigate the asymptotic behavior of the ground state energy of the Fr\"ohlich Hamiltonian for a Fermionic multipolaron in the so-called strong coupling limit. We prove that it is given to leading order by the ground state energy of the Pekar-Tomasevich functional with Fermionic statistics, which is a much simpler model. Our main theorem is new because none of the previous results on the strong coupling limit have taken into account the Fermionic statistics and the spin of the electrons. A binding result for Fr\"ohlich multipolarons is a corollary of our main theorem combined with the binding result for multipolarons in the Pekar-Tomasevich model by the first author and Griesemer in [AG14]. Our analysis strongly relies on the work of Wellig [Well15] which in turn used and generalized methods developed by Lieb and Thomas [LT97], Frank, Lieb, Seiringer and Thomas [FLST11] and Griesemer and Wellig [GW13]. In order to take the Fermionic statistics into account, we employ a localization method given by Lieb and Loss in [LL05]

Induced fractional valley number in graphene with topological defects

We report on the possibility of valley number fractionalization in graphene with a topological defect that is accounted for in Dirac equation by a pseudomagnetic field. The valley number fractionalization is attributable to an imbalance on the number of one particle states in one of the two Dirac points with respect to the other and it is related to the flux of the pseudomagnetic field. We also discuss the analog effect the topological defect might lead in the induced spin polarization of the charge carriers in graphene

Contagion of currency crises: Some theoretical and empirical analysis

This paper investigates contagion effects. In a model with highly and lowly informed investors we show that a currency crisis in one country can trigger a crisis in another country. Portfolio losses of the highly informed investors in one country will force them to withdraw capital from the other country. The behavior of the lowly informed investors multiplies this effect and the other country becomes more and more vulnerable. In the empirical part we focus on the Asian crisis (1997/98). Using a LOGIT approach we can show that contagion, in the sense of a crisis not explainable by economic fundamentals but by exchange rate losses resulting from investment in other countries, seems to have caused the currency crises of the Philippines and especially of Singapore. --Contagion,Currency crises,Asian crisis