14594667
Moduli space and phase structure of heterotic strings in two dimensions
We explore the moduli space of heterotic strings in two dimensions. In doing so, we introduce new lines of compactified theories with Spin(24) gauge symmetry and discuss compactifications with Wilson lines. The phase structure of $d=2$ heterotic string theory is examined by classifying the hypersurfaces in moduli space which support massless quanta or discrete states. Finally, we compute the torus amplitude over much of the moduli space.
17373607
Precision Entropy of Spinning Black Holes
We construct spinning black hole solutions in five dimensions that take into account the mixed gauge-gravitational Chern-Simons term and its supersymmetric completion. The resulting entropy formula is discussed from several points of view. We include a Taub-NUT base space in order to test recent conjectures relating 5D black holes to 4D black holes and the topological string. Our explicit results show that certain charge shifts have to be taken into account for these relations to hold. We also compute corrections to the entropy of black rings in terms of near horizon data.
118543383
Twisted Inflation
We present a new mechanism for slow-roll inflation based on higher dimensional supersymmetric gauge theory compactified to four dimensions with twisted (supersymmetry breaking) boundary conditions. These boundary conditions lead to a potential for directions in field space that would have been flat were supersymmetry preserved. For field values in these directions much larger than the supersymmetry-breaking scale, the flatness of the potential is nearly restored. Starting in this nearly flat region, inflation can occur as the theory relaxes towards the origin of field space. Near the origin, the potential becomes steep and the theory quickly descends to a confining gauge theory in which the inflaton does not exist as a particle. This confining gauge theory could be part of the Standard Model (QCD) or a natural dark matter sector; we comment on various scenarios for reheating. As a specific illustration of this mechanism, we discuss 4+1 dimensional maximally supersymmetric gauge theory on a circle with antiperiodic boundary conditions for fermions. When the theory is weakly coupled at the compactification scale, we calculate the inflaton potential directly in field theory by integrating out the heavy W-bosons and their superpartners. At strong coupling the model can be studied using a gravity dual, which realizes a new model of brane inflation on a non-supersymmetric throat geometry. Assuming there exists a UV completion that avoids the η-problem, predictions from our model are consistent with present observations, and imply a small tensor-to-scalar ratio. e-mail: jdavis@phas.ubc.ca e-mail: tslevi@phas.ubc.ca e-mail: mav@phas.ubc.ca e-mail: kwhyte@phas.ubc.ca ar X iv :1 00 4. 53 85 v1 [ he pth ] 2 9 A pr 2 01 0
14709760
Particle production in matrix cosmology
We consider cosmological particle production in 1+1 dimensional string theory. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum fields in time-dependent backgrounds is resolved by the underlying matrix model. This leads to a finite energy density for the "in" state which cancels the effect of anomalous particle production.
10413170
Boundary counterterms and the thermodynamics of 2-D black holes
We utilize a novel method to study the thermodynamics of two dimensional type 0A black holes with constant RR flux. Our approach is based on the Hamilton-Jacobi method of deriving boundary counterterms. We demonstrate this approach by recovering the standard results for a well understood example, Witten's black hole. Between this example and the 0A black hole we find universal expressions for the entropy and black hole mass, as well as the infra-red divergence of the partition function. As a non-trivial check of our results we verify the first law of thermodynamics for these systems. Our results for the mass disagree with the predictions of a proposed matrix model dual of the 0A black hole.
119206090
Flavor-symmetry breaking with charged probes
A bstractWe discuss the recombination of brane/anti-brane pairs carrying D3 brane charge in AdS5 × S5. These configurations are dual to co-dimension one defects in the $ \mathcal{N} $ = 4 super-Yang-Mills description. Due to their D3 charge, these defects are actually domain walls in the dual gauge theory, interpolating between vacua of different gauge symmetry. A pair of unjoined defects each carry localized (2 + 1) dimensional fermions and possess a global U(N) × U(N) flavor symmetry while the recombined brane/anti-brane pairs exhibit only a diagonal U(N). We study the thermodynamics of this flavor-symmetry breaking under the influence of external magnetic field.
118366559
Searching for GeV-scale new Gauge Bosons in QGP thermal dilepton production
In this paper we propose to use the measurement of the thermal Quark-Gluon Plasma (QGP) dilepton spectra in the Intermediate Mass Region (IMR) of heavy-ion collisions, as a new method to search for GeV-scale dark gauge bosons (gamma' or Z'). Such light mediators are a common feature of light (i.e. low mass) dark matter scenarios, which have been invoked to explain puzzling signals in dark matter indirect and direct detection experiments. First we show that a light gamma' or Z' will generate a resonant enhancement of the dilepton spectrum produced thermally by the QGP, at an energy corresponding to the dark gauge boson mass. Secondly, using data from the PHENIX experiment, we are able to set an upper limit on the combined coupling of this new gauge boson to quarks and leptons (independently of their vectorial or axial nature) chi_q chi_e < 10^(-3) at the 95% confidence level for a gauge boson mass in the range 1.5 - 2.5 GeV. This result complements previous searches for new light gauge bosons and probes a new region of the parameter space, particularly interesting in the case of non-universal couplings to quarks and leptons. Prospects for the discovery of such a boson by the ALICE collaboration are also discussed.
54708481
New method for analyzing dark matter direct detection data
The experimental situation of dark matter direct detection has reached an exciting crossroads, with potential hints of a discovery of dark matter (DM) from the CDMS, CoGeNT, CRESST-II and DAMA experiments in tension with null results from xenon-based experiments such as XENON100 and LUX. Given the present controversial experimental status, it is important that the analytical method used to search for DM in direct detection experiments is both robust and flexible enough to deal with data for which the distinction between signal and background points is difficult, and hence where the choice between setting a limit or defining a discovery region is debatable. In this article we propose a novel (Bayesian) analytical method, which can be applied to all direct detection experiments and which extracts the maximum amount of information from the data. We apply our method to the XENON100 experiment data as a worked example, and show that firstly our exclusion limit at 90% confidence is in agreement with their own for the 225 live days data, but is several times stronger for the 100 live days data. Secondly we find that, due to the two points at low values of S1 and S2 in the 225 days data set, our analysis points to either weak consistency with low-mass dark matter or the possible presence of an unknown background. Given the null result from LUX, the latter scenario seems the more plausible.