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

SUL(4)×U(1)SU_{L}(4)\times U(1) model for electroweak unification and sterile neutrinos

Some of basic problems in neutrino physics such as new energy scales, the enormous gap between neutrino masses and the lightest charged fermion mass, possible existance of sterile neutrinos in eV mass range are studied in the local gauge group $SU_{L}(4)\times U(1)$ for electroweak unification, which does not contain fermions with exotic electric charges. It is shown that neutrino mass spectrum can be decoupled from that of the other fermions. Further normal seesaw mechanism for neutrinos, with right handed neutrino Majorana masses to be of order $M\gg M_{\text{weak}}$ as well a new eV-scale can be accomodated. The eV-scale seesaw may manifest itself in experiments like Liquid Scintilation Neutrino Detector (LSND) and MiniBooNE (MB) experimental results and future neutrino experiments.Comment: 13 page

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

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

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

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

SU_L(4) x U(1) model for electroweak unification

After some general remarks about SU_L(4) electroweak unification, the model is extended to SU_L(4)xU_X(1) to accomodate fractionally charged quarks. The unification scale is expected to be in TeV region. A right-handed Majorana neutrino along with known lepton are put in the fundamental representation of SU_L(4) with Y_X=0. The see-saw mechanism for neutrino masses and flavor mixing in neutrino sector is a natural feature of the model. The lepton number violating processes can occure through dilepton gauge bosons contained in the model.Comment: RevTeX, 9 pages, no figure: replaced with revised versio