Canonical Seesaw Mechanism in Electro-Weak SU(4)L x U(1)Y Models

In this paper we prove that the canonical seesaw mechanism can naturally be implemented in a particular class of electro-weak SU(4)L x U(1)Y gauge models. The resulting neutrino mass spectrum is determined by just tuning a unique free parameter 'a' within the algebraical method of solving gauge models with high symmetries. All the Standard Model phenomenology is preserved, being unaffected by the new physics occuring at a high breaking scale m ~ 10^11GeV.Comment: 12 pages, 1 Table, no figure

Boson mass spectrum in SU(4)L⊗U(1)YSU(4)_L\otimes U(1)_Y model with exotic electric charges

The boson mass spectrum of the electro-weak \textbf{$SU(4)_{L}\otimes U(1)_{Y}$} model with exotic electric charges is investigated by using the algebraical approach supplied by the method of exactly solving gauge models with high symmetries. Our approach predicts for the boson sector a one-parameter mass scale to be tuned in order to match the data obtained at LHC, LEP, CDF.Comment: 12 pages, 1 Table with numerical estimates and 1 Figure added, mistaken results correcte

Calabi-Yau 3-folds from 2-folds

We consider type IIA string theory on a Calabi-Yau 2-fold with D6-branes wrapping 2-cycles in the 2-fold. We find a complete set of conditions on the supergravity solution for any given wrapped brane configuration in terms of SU(2) structures. We reduce the problem of finding a supergravity solution for the wrapped branes to finding a harmonic function on R$\times$CY$_2$. We then lift this solution to 11-dimensions as a product of R$^{(4.1)}$ and a Calabi-Yau 3-fold. We show how the metric on the 3-fold is determined in terms of the wrapped brane solution. We write down the distinguished (3,0) form and the K{\"a}hler form of the 3-fold in terms of structures defined on the base 2-d complex manifold. We discuss the topology of the 3-fold in terms of the D6-branes and the underlying 2-fold. We show that in addition to the non-trivial cycles inherited from the underlying 2-fold there are $N-1$ new 2-cycles. We construct closed (1,1) forms corresponding to these new cycles. We also display some explicit examples. One of our examples is that of D6-branes wrapping the 2-cycle in an A$_1$ ALE space, the resulting 3-fold has $h^{(1,1)}=N$, where $N$ is the number of D6-branes.Comment: 30 page

That's a wrap!

Calibration technology provides us with a fast and elegant way to find the supergravity solutions for BPS wrapped M-branes. Its true potential had however remained untapped due to the absence of a classification of calibrations in spacetimes with non-trivial flux. The applications of this method were thus limited in practise to M-branes wrapping Kahler calibrated cycles. In this paper, we catagorize a type of generalised calibrations which exist in supergravity backgrounds and contain Kahler calibrations as a sub-class. This broadens the arena of brane configurations whose supergravity solutions are accessible through the calibration 'short-cut' method.Comment: 19 pages, typos correcte

Supergravity Solution of Intersecting Branes and AdS/CFT with Flavor

We construct the supergravity solution for fully localized D2/D6 intersection. The near horizon limit of this solution is the supergravity dual of supersymmetric Yang-Mills theory in 2+1 dimensions with flavor. We use this solution to formulate mirror symmetry of 2+1 dimensional gauge theories in the language of AdS/CFT correspondence. We also construct the supergravity dual of a non-commutative gauge theory with fundamental matter.Comment: 17 Pages, 2 figures, references added. Minor corrections to eqs (5.3) and (5.4

Linear Dilaton Background and Fully Localized Intersecting Five-branes

We investigate a near-horizon geometry of NS5-branes wrapping on a Riemann surface, which asymptotically approaches to linear dilaton backgrounds. We concretely find a fully localized solution of the near-horizon geometry of intersecting NS5-branes. We also discuss a relation to a description of Landau-Ginzburg theories.Comment: 1+16 pages, latex, no figures, references adde

A note on bosonic open strings in constant B field

We sketch the main steps of old covariant quantization of bosonic open strings in a constant $B$ field background. We comment on its space-time symmetries and the induced effective metric. The low-energy spectrum is evaluated and the appearance of a new non-commutative gauge symmetry is addressed.Comment: 13 pages, Latex, important comments added, to appear in PR

A Brane Teaser

In this note we study the puzzle posed by two M5-branes intersecting on a string (or equivalently, a single M5-brane wrapping a holomorphic four-cycle in C^4). It has been known for a while that this system is different from all other configurations built using self-intersecting M-branes; in particular the corresponding supergravity solution exhibits various curious features which have remained unexplained. We propose that the resolution to these puzzles lies in the existence of a non-zero two-form on the M5-brane world-volume.Comment: 21 pages. References adde