9262146
Open-string BRST cohomology for generalized complex branes
It has been shown recently that the geometry of D-branes in general topologically twisted (2,2) sigma-models can be described in the language of generalized complex (GC) structures. On general grounds, such D-branes (called GC branes) must form a category. We compute the BRST cohomology of open strings with both ends on the same GC brane. In mathematical terms, we determine spaces of endomorphisms in the category of GC branes. We find that the BRST cohomology can be expressed as the cohomology of a Lie algebroid canonically associated to any GC brane. In the special case of B-branes, this leads to an apparently new way to compute Ext groups of holomorphic line bundles supported on complex submanifolds: while the usual method leads to a spectral sequence converging to the Ext, our approach expresses the Ext group as the cohomology of a certain differential acting on the space of smooth sections of a graded vector bundle on the submanifold. In the case of coisotropic A-branes, our computation confirms a proposal of Orlov and one of the authors (A.K.).
120831466
Noncoplanarity effects in proton-proton bremsstrahlung
Noncoplanarity in proton-proton bremsstrahlung is investigated. Significant effects are observed for certain photon polar angles, psi(gamma). Such noncoplanarity effects, not of dynamical origin, are possibly responsible for past disagreements between theory and experiment. The Harvard noncoplanar coordinate system, which avoids kinematic singularities in the cross section, is used in our calculations and is recommended for use in the analysis of experimental data. Alternative methods of presenting cross sections are discussed. [S0556-2813(98)50110-0].
18559665
Topological sigma-models with H-flux and twisted generalized complex manifolds
We study the topological sector of N = 2 sigma-models with HH-flux. It has been known for a long time that the target-space geometry of these theories is not Kahler and can be described in terms of a pair of complex structures, which do not commute, in general, and are parallel with respect to two different connections with torsion. Recently an alternative description of this geometry was found, which involves a pair of commuting twisted generalized complex structures on the target space. In this paper, we define and study the analogs of A and B-models for N = 2 sigma-models with HH-flux and show that the results are naturally expressed in the language of twisted generalized complex geometry. For example, the space of topological observables is given by the cohomology of a Lie algebroid associated to one of the two twisted generalized complex structures. We determine the topological scalar product, which endows the algebra of observables with the structure of a Frobenius algebra. We also discuss mirror symmetry for twisted generalized Calabi-Yau manifolds.
123491963
Noncoplanarity in proton-proton bremsstrahlung
Using the soft-photon approximation, we address the issue of the importance of noncoplanarity effects in proton-proton bremsstrahlung, We investigate the noncoplanar cross section as a function of the noncoplanarity angle (φ) over bar for the entire range of the photon polar angle psi(gamma). The (φ) over bar dependence is shown to provide a significant variation in the cross section, for a given psi(gamma). Thus, there can be some uncertainty in determining experimental coplanar cross sections. To avoid the phase-space singularities of spherical geometry. we utilize the Harvard noncoplanar geometry. A detailed explication of the Harvard geometry is provided, Comparison of our calculations with experimental data is included.
115635245
Topological sigma models and generalized geometries
We study the relation between topological sigma models and generalized geometries. The existence conditions for the most general type of topological sigma models obtained from twisting the N=(2,2) supersymmetric sigma model are investigated, and are found to be related to twisted generalized Calabi-Yau structures. The properties of these topological sigma models are analyzed in detail. The observables are shown to be described by the cohomology of a Lie algebroid, which is intrinsically associated with the twisted generalized Calabi-Yau structure. The Frobenius structure on the space of states and the effects of instantons are analyzed. We also study D-branes in these topological sigma models, and demonstrate that they also admit descriptions in terms of generalized geometries.
13345134
D-branes in topological minimal models: the Landau–Ginzburg approach
We study D-branes in topologically twisted N = 2 minimal models using the Landau-Ginzburg realization. In the cases of A and D-type minimal models we provide what we believe is an exhaustive list of topological branes and compute the corresponding boundary OPE algebras as well as all disk correlators. We also construct examples of topological branes in E-type minimal models. We compare our results with the boundary state formalism, where possible, and find agreement.
7025505
Exact Analysis of Scaling and Dominant Attractors Beyond the Exponential Potential
By considering the potential parameter Γ as a function of another potential parameter λ (Zhou et al 2008 Phys. Lett. B 660 7–12), we successfully extend the analysis of a two-dimensional autonomous dynamical system of a quintessence scalar field model to the analysis of a three-dimensional system, which enables us to study the critical points of a large number of potentials beyond the exponential potential exactly. We find that there are ten critical points in all, three points P3,5,6 are general points which are possessed by all quintessence models regardless of the form of potentials and the rest of the points are closely connected to the concrete potentials. It is quite surprising that, apart from the exponential potential, there are a large number of potentials which can give a scaling solution when the function f(λ)(=Γ(λ) − 1) equals zero for one or some values of λ and if the parameter λ also satisfies condition (16) or (17) at the same time. We give the differential equations to derive these potentials V() from f(λ). We also find that, if some conditions are satisfied, the de-Sitter-like dominant point P4 and the scaling solution point P9 (or P10) can be stable simultaneously unlike P9 and P10. Although we survey scaling solutions beyond the exponential potential for ordinary quintessence models in standard general relativity, this method can be applied to other extensively scaling solution models studied in the literature (Copeland et al 2006 Int. J. Mod. Phys. D 15 1753) including coupled quintessence, (coupled-)phantom scalar field, k-essence and even beyond the general relativity case H2 ∝ ρnT. We also discuss the disadvantage of our approach.
4995821
Drell-Yan lepton pair production at NNLO QCD with parton showers
We present a simple approach to combine NNLO QCD calculations and parton showers, based on the unlops technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.
119109759
Q(6) flavor symmetry model for the extension of the minimal standard model by three right-handed sterile neutrinos
The extension of the minimal standard model by three right-handed sterile neutrinos with masses smaller than the electroweak scale (nu MSM) is discussed in a Q(6) flavor symmetry framework. The lightness of the keV sterile neutrino and the near mass degeneracy of two heavier sterile neutrinos are naturally explained by exploiting group properties of Q(6). A normal hierarchical mass spectrum and an approximately mu-tau symmetric mass matrix are predicted for three active neutrinos. Nonzero theta(13) can be obtained together with a deviation of theta(23) from the maximality, where both mixing angles are consistent with the latest global data including T2K and MINOS results. Furthermore, the tiny active-sterile mixing is related to the mass ratio between the lightest active and lightest sterile neutrinos.
118708445
Jet vetoes for Higgs boson production at future hadron colliders
We study Higgs boson production in exclusive jet bins at possible future 33 and 100 TeV proton-proton colliders. We compare the cross sections obtained using fixed-order perturbation theory with those obtained by also resuming large logarithms induced by the jet-binning in the gluon-fusion and associated production channels. The central values obtained by the best-available fixed-order predictions differ by $10-20\%$ from those obtained after including resummation over the majority of phase-space regions considered. Additionally, including the resummation dramatically reduces the residual scale variation in these regions, often by a factor of two or more. We further show that in several new kinematic regimes that can be explored at these high-energy machines, the inclusion of resummation improvement is mandatory.
116807042
Disentangling radiative corrections using the high-mass Drell-Yan process at the LHC
We present a detailed numerical study of lepton-pair production via the Drell-Yan process above the Z-peak at the LHC. Our results consistently combine next-to-next-to-leading order QCD corrections and next-to-leading order electroweak effects, and include the leading photon-initiated processes using a recent extraction of the photon distribution function. We focus on the effects of electroweak corrections and of photon-photon scattering contributions, and demonstrate which kinematic distributions exhibit sensitivity to these corrections. We show that a combination of measurements allows them to be disentangled and separately determined.