413 research outputs found
Fermion Masses at intermediate Tan(beta): Unification of Yukawa Determinants
In the context of the Grand Unified MSSM, we investigate the fermion mass
matrices at GUT scale. We note that from the experimental mass pattern the
determinants of the Yukawa matrices at this scale can be unified with good
precision. Taking the unification o determinants as an hypothesis, it gives two
model independent predictions that in the MSSM turns out to determine an
appropriate value for the product m_d m_s and tan(beta)~7-10 in the favored
range. We then review a predictive model of SU(3) flavour in the context of
supersymmetric SO(10) that nicely implements this mechanism, while explaining
all fermion masses and mixings at 1 sigma level, including neutrino data.Comment: to Appear in the proceedings of "QUARKS-2006
Standard Model and Gravity from Spinors
We propose to unify the Gravity and Standard Model gauge groups by using
algebraic spinors of the standard four-dimensional Clifford algebra, in
left-right symmetric fashion. This generates exactly a Standard Model family of
fermions, and a Pati-Salam unification group emerges, at the Planck scale,
where (chiral) self-dual gravity decouples. As a remnant of the unification,
isospin-triplets spin-two particles may naturally appear at the weak scale,
providing a striking signal at the LHC.Comment: 7 pages, added clarification
Three dimensional large N monopole gas
We study the large N limit in the presence of magnetic monopoles in the
Yang-Mills/Higgs model in three dimensions. The physics in the limit depends
strongly on the distribution of eigenvalues of the Higgs field in the vacuum,
and we propose a particular, nondegenerate configuration. It minimizes the free
energy at the moment of symmetry breaking. Given this, the magnetic monopoles
show a wide hierarchy of masses, and some are vanishing as 1/N. The dilute gas
picture, then, provides an interesting structure in the large N limit.Comment: 36 pages, 5 figures, changes in style, organization and small errors
correcte
Graviweak Unification
The coupling of chiral fermions to gravity makes use only of the selfdual
SU(2) subalgebra of the (complexified) SO(3,1) algebra. It is possible to
identify the antiselfdual subalgebra with the SU(2)_L isospin group that
appears in the Standard Model, or with its right-handed counterpart SU(2)_R
that appears in some extensions. Based on this observation, we describe a form
of unification of the gravitational and weak interactions. We also discuss
models with fermions of both chiralities, the inclusion strong interactions,
and the way in which these unified models of gravitational and gauge
interactions avoid conflict with the Coleman-Mandula theorem.Comment: 18 pages, typos corrected and improved wordin
Multi-Matrix Models: Integrability Properties and Topological Content
We analyze multi--matrix chain models. They can be considered as
multi--component Toda lattice hierarchies subject to suitable coupling
conditions. The extension of such models to include extra discrete states
requires a weak form of integrability. The discrete states of the --matrix
model are organized in representations of . We solve exactly the
Gaussian--type models, of which we compute several all-genus correlators. Among
the latter models one can classify also the discretized string theory,
which we revisit using Toda lattice hierarchy methods. Finally we analyze the
topological field theory content of the --matrix models: we define primary
fields (which are ), metrics and structure constants and prove that
they satisfy the axioms of topological field theories. We outline a possible
method to extract interesting topological field theories with a finite number
of primaries.Comment: 31 pages, Late
Matrix String Theory, 2D SYM Instantons and affine Toda systems
Extending a recent result of S.B. Giddings, F. Hacquebord and H. Verlinde, we
show that in the U(N) SYM Matrix theory there exist classical BPS instantons
which interpolate between different closed string configurations via
joining/splitting interactions similar to those of string field theory. We
construct them starting from branched coverings of Riemann surfaces. For the
class of them which we analyze in detail the construction can be made explicit
in terms U(N) affine Toda field theories.Comment: 12 pages, 1 eps figure, JHEP.cls LaTeX2e class file; sign corrected,
ref. and acknowledgements update
Heterotic Matrix String Theory and Riemann Surfaces
We extend the results found for Matrix String Theory to Heterotic Matrix
String Theory, i.e. to a 2d O(N) SYM theory with chiral (anomaly free) matter
and N=(8,0) supersymmetry. We write down the instanton equations for this
theory and solve them explicitly. The solutions are characterized by branched
coverings of the basis cylinder, i.e. by compact Riemann surfaces with
punctures. We show that in the strong coupling limit the action becomes the
heterotic string action plus a free Maxwell action. Moreover the amplitude
based on a Riemann surface with p punctures and h handles is proportional to
g^{2-2h-p}, as expected for the heterotic string interaction theory with string
coupling g_s=1/g.Comment: 17 pages, JHEP LaTeX style, sentence delete
Chirality in unified theories of gravity
We show how to obtain a single chiral family of an SO(10) GUT, starting from
a Majorana-Weyl representation of a unifying ("GraviGUT") group SO(3,11), which
contains the gravitational Lorentz group SO(3,1). An action is proposed, which
reduces to the correct fermionic GUT action in the broken phase.Comment: 7 pages. Discussion clarified. Version matching the published on
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