The Ruled Vertex and Nontoric del Pezzo Surfaces

We construct the topological partition function of local nontoric del Pezzo surfaces using the ruled vertex formalism.Comment: 16 pages, 4 figure

Seismogeological Features of the Crust in Romania

The Romanian area consists of old consolidated units of pre-Alpine age (the Moesian, Moldavian and Scythian platforms) and Alpine orogenic units (the Carpathian arc and North-Dobrudjan orogen). General seismogeological peculiarities of the pre-Alpine tectonic units are presented, as well as some structural characteristics of the Transylvanian Basin and the Pannonian Depression. Both shallow and deep seismic reflection/refraction data as well as log information and some potential field data were used for the investigation of the crustal structure. The varibility in the seismogeological pattern and crustal thickness shown by the different tectonic units is due to the differences in structure and lithology as well as to differences in crustal age. Some general characteristics are presented as an overall seismogeological image

Prepotentials for local mirror symmetry via Calabi-Yau fourfolds

In this paper, we first derive an intrinsic definition of classical triple intersection numbers of K_S, where S is a complex toric surface, and use this to compute the extended Picard-Fuchs system of K_S of our previous paper, without making use of the instanton expansion. We then extend this formalism to local fourfolds K_X, where X is a complex 3-fold. As a result, we are able to fix the prepotential of local Calabi-Yau threefolds K_S up to polynomial terms of degree 2. We then outline methods of extending the procedure to non canonical bundle cases.Comment: 42 pages, 7 figures. Expanded, reorganized, and added a theoretical background for the calculation

From E_8 to F via T

We argue that T-duality and F-theory appear automatically in the E_8 gauge bundle perspective of M-theory. The 11-dimensional supergravity four-form determines an E_8 bundle. If we compactify on a two-torus, this data specifies an LLE_8 bundle where LG is a centrally-extended loopgroup of G. If one of the circles of the torus is smaller than sqrt(alpha') then it is also smaller than a nontrivial circle S in the LLE_8 fiber and so a dimensional reduction on the total space of the bundle is not valid. We conjecture that S is the circle on which the T-dual type IIB theory is compactified, with the aforementioned torus playing the role of the F-theory torus. As tests we reproduce the T-dualities between NS5-branes and KK-monopoles, as well as D6 and D7-branes where we find the desired F-theory monodromy. Using Hull's proposal for massive IIA, this realization of T-duality allows us to confirm that the Romans mass is the central extension of our LE_8. In addition this construction immediately reproduces the conjectured formula for global topology change from T-duality with H-flux.Comment: 25 pages, 4 eps figure

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

Flavour from partially resolved singularities

In this letter we study topological open string field theory on D--branes in a IIB background given by non compact CY geometries ${\cal O}(n)\oplus{\cal O}(-2-n)$ on $\P1$ with a singular point at which an extra fiber sits. We wrap $N$ D5-branes on $\P1$ and $M$ effective D3-branes at singular points, which are actually D5--branes wrapped on a shrinking cycle. We calculate the holomorphic Chern-Simons partition function for the above models in a deformed complex structure and find that it reduces to multi--matrix models with flavour. These are the matrix models whose resolvents have been shown to satisfy the generalized Konishi anomaly equations with flavour. In the $n=0$ case, corresponding to a partial resolution of the $A_2$ singularity, the quantum superpotential in the ${\cal N}=1$ unitary SYM with one adjoint and $M$ fundamentals is obtained. The $n=1$ case is also studied and shown to give rise to two--matrix models which for a particular set of couplings can be exactly solved. We explicitly show how to solve such a class of models by a quantum equation of motion technique

An Unusual Hydrogen Migration/C−H Activation Reaction with Group 3 Metals

A novel hydrogen migration from the phenyl ring to the pyridine ring of an yttrium pyridyl complex supported by a 1,1′-ferrocene diamide ligand is reported. Density functional theory calculations were instrumental in probing the mechanism for this transformation

Fractional two-branes, toric orbifolds and the quantum McKay correspondence

We systematically study and obtain the large-volume analogues of fractional two-branes on resolutions of orbifolds C^3/Z_n. We study a generalisation of the McKay correspondence proposed in hep-th/0504164 called the quantum McKay correspondence by constructing duals to the fractional two-branes. Details are explicitly worked out for two examples -- the crepant resolutions of C^3/Z_3 and C^3/Z_5.Comment: 34 pages, 2 figures, LaTeX (JHEP3 style); (v2) typos corrected; (v3) sec 3 reorganise

M-theory, the signature theorem, and geometric invariants

The equations of motion and the Bianchi identity of the C-field in M-theory are encoded in terms of the signature operator. We then reformulate the topological part of the action in M-theory using the signature, which leads to connections to the geometry of the underlying manifold, including positive scalar curvature. This results in a variation on the miraculous cancellation formula of Alvarez-Gaum\'e and Witten in twelve dimensions and leads naturally to the Kreck-Stolz s-invariant in eleven dimensions. Hence M-theory detects diffeomorphism type of eleven-dimensional (and seven-dimensional) manifolds, and in the restriction to parallelizable manifolds classifies topological eleven-spheres. Furthermore, requiring the phase of the partition function to be anomaly-free imposes restrictions on allowed values of the s-invariant. Relating to string theory in ten dimensions amounts to viewing the bounding theory as a disk bundle, for which we study the corresponding phase in this formulation.Comment: 17 page