Cosmic D--term Strings as Wrapped D3 Branes

We describe cosmic D--term strings as D3 branes wrapped on a resolved conifold. The matter content that gives rise to D--term strings is shown to describe the world--volume theory of a space--filling D3 brane transverse to the conifold which itself is a wrapped D5 brane. We show that, in this brane theory, the tension of the wrapped D3 brane mathces that of the D--term string. We argue that there is a new type of cosmic string which arises from fractional D1 branes on the world--volume of a fractional D3 brane.Comment: 13 pages in phyzzx.tex; eq. (17) corrected, other minor corrections; v3: more minor correction

Strings and the Holographic Description of Asymptotically de Sitter Spaces

Asymptotically de Sitter spaces can be described by Euclidean boundary theories with entropies given by the modified Cardy--Verlinde formula. We show that the Cardy--Verlinde formula describes a string with a rescaled tension which in fact is a string at the stretched cosmological horizon as seen from the boundary. The temperature of the boundary theory is the rescaled Hagedorn temperature of the string. Our results agree with an alternative description of asymptotically de Sitter spaces in terms of strings on the stretched horizon. The relation between the two descriptions is given by the large gravitational redshift between the boundary and the stretched horizon and a shift in energy.Comment: 15 pages in phyzzx.tex, minor correction

Hierarchical Supersymmetry Breaking in Superstring Derived Standard--like Models

We examine the problem of supersymmetry breaking in realistic superstring standard--like models which are constructed in the free fermionic formulation. We impose a supersymmetric vacuum at the Planck scale by requiring vanishing F and D constraints at the cubic level of the superpotential. We then study possible scenarios for supersymmetry breaking by examining the role of nonrenormalizable terms and hidden sector gaugino and matter condensates. We argue that in some scenarios hierarchical supersymmetry breaking in the observable sector is possible.Comment: IASSNS-HEP-94/17, 31 pages, phyzz

Domain Walls on Singularities

We describe domain walls that live on $A_2$ and $A_3$ singularities. The walls are BPS if the singularity is resolved and non--BPS if it is deformed and fibered. We show that these domain walls may interpolate between vacua that support monopoles and/or vortices.Comment: 16 pages in phyzzx.te

Inflation on Fractional Branes: D--Brane Inflation as D--Term Inflation

We describe a D--brane inflation model which consists of two fractional D3 branes separated on a transverse $T^2 \times K3$. Inflation arises due to the resolved orbifold singularity of $K3$ which corresponds to an anomalous D--term on the brane. We show that D--brane inflation in the bulk corresponds to D--term inflation on the brane. The inflaton and the trigger field parametrize the interbrane distances on $T^2$ an $K3$ respectively. After inflation the branes reach a supersymmetric configuration in which they are at the origin of $T^2$ but separated along the $K3$ directions.Comment: 15 pages in phyzzx.tex; minor corrections including all factors of 2\pi; v3: more minor correction

Black Hole Entropy and Superconformal Field Theories on Brane-Antibrane Systems

We obtain the enropy of Schwarzschild and charged black holes in D>4 from superconformal gases that live on p=10-D dimensional brane-antibrane systems wrapped on T^p. The preperties of the strongly coupled superconformal theories such as the appearance of hidden dimensions (for p=1,4) and fractional strings (for p=5) are crucial for our results. In all cases, the Schwarzschild radius is given by the transverse fluctuations of the branes and antibranes due to the finite temperature. We show that our results can be generalized to multicharged black holes.Comment: 24 pages in phyzzx.te

Evaluation of the Theoretical Uncertainties in the W to Lepton and Neutrino Cross Sections at the LHC

We study the sources of systematic errors in the measurement of the W to lepton and neutrino cross-sections at the LHC. We consider the systematic errors in both the total cross-section and acceptance for anticipated experimental cuts. We include the best available analysis of QCD effects at NNLO in assessing the effect of higher order corrections and PDF and scale uncertainties on the theoretical acceptance. In addition, we evaluate the error due to missing NLO electroweak corrections and propose which MC generators and computational schemes should be implemented to best simulate the events.Comment: 33 pages, 109 eps figures, uses JHEP3.cls, rotating.sty Version 2 corrects an error in Table 1, adds some references, and updates an author addres

On the Cardy-Verlinde Formula and the de Sitter/CFT Correspondence

We derive the Cardy--Verlinde entropy formula for the field theory that lives on the boundary of an asymptotically de Sitter space with a black hole. The boundary theory which is not conformal has a monotonic $C$--function defined by the Casimir energy. The instability of the space due to Hawking radiation from the black hole corresponds to an RG flow from the IR to the UV during which $C$ increases. The endpoint of black hole evaporation is de Sitter space which is described by a conformal theory at the UV fixed point of the RG flow.Comment: 16 pages in phyzzx.tex, the discussion in section 4 clarified, minor corrections, two references added; v3: the relation between time evolution and RG flow made explicit, Comments and references adde