179 research outputs found
Lepton Number Violation in Supersymmetric Grand Unified Theories
We argue that the nature of the global conservation laws in Supersymmetric
Grand Unified Theories is determined by the basic vacuum configuration in the
model rather than its Lagrangian. It is shown that the suppression of baryon
number violation in a general (R-parity violating) superpotential can naturally
appear in some extended SU(N) SUSY GUTs which, among other degenerate
symmetry-breaking vacua, have a missing VEV vacuum configuration giving a
solution to the doublet-triplet splitting problem. We construct SU(7) and SU(8)
GUTs where the effective lepton number violating couplings immediately evolve,
while the baryon number non-conserving ones are safely projected out as the GUT
symmetry breaks down to that of the MSSM. However at the next stage, when SUSY
breaks, the radiative corrections shift the missing VEV components to some
nonzero values of order M_{SUSY}, thereby inducing the ordinary Higgs doublet
mass, on the one hand, and tiny baryon number violation, on the other. So, a
missing VEV solution to the gauge hierarchy problem leads at the same time to a
similar hierarchy of baryon vs lepton number violation.Comment: 15 page LaTeX fil
The b--unification in GUTs with non-chiral matter
It is shown, that the presently accepted value for b-quark mass can be
obtained from the requirement of the exact b- unification in the both
non-SUSY and SUSY non-chiral extended GUTs.Comment: 10 pages, LaTeX, 4 LaTeX figures include
Spontaneously Generated Tensor Field Gravity
An arbitrary local theory of a symmetric two-tensor field in
Minkowski spacetime is considered, in which the equations of motion are
required to be compatible with a nonlinear length-fixing constraint leading to spontaneous Lorentz invariance violation, SLIV
( is the proposed scale for SLIV). Allowing the parameters in the Lagrangian
to be adjusted so as to be consistent with this constraint, the theory turns
out to correspond to linearized general relativity in the weak field
approximation, while some of the massless tensor Goldstone modes appearing
through SLIV are naturally collected in the physical graviton. In essence the
underlying diffeomophism invariance emerges as a necessary condition for the
tensor field not to be superfluously restricted in degrees of
freedom, apart from the constraint due to which the true vacuum in the theory
is chosen by SLIV. The emergent theory appears essentially nonlinear, when
expressed in terms of the pure Goldstone tensor modes and contains a plethora
of new Lorentz and violating couplings. However, these couplings do not
lead to physical Lorentz violation once this tensor field gravity is properly
extended to conventional general relativity.Comment: 27 pages, published version, to appear in Nuclear Physics
Deriving Gauge Symmetry and Spontaneous Lorentz Violation
We consider a class of field theories with a four-vector field
in addition to other fields supplied with a global charge symmetry - theories
which have partial gauge symmetry in the sense of only imposing it on those
terms in the Lagrangian density which have derivatives as factors in them. We
suppose that spontaneous Lorentz invariance breaking occurs in such a theory
due to the four-vector field taking a non-zero vacuum expectation value. Under
some very mild assumptions, we show that this Lorentz violation is not
observable and the whole theory is practically gauge invariant. A very
important presupposition for this theorem is that an initial condition is
imposed on the no-derivative expressions corresponding to the early Universe
being essentially in a vacuum state. This condition then remains true forever
and can be interpreted as a gauge constraint. We formulate the conditions under
which the spontaneous Lorentz violation becomes observable. Spontaneously
broken Lorentz invariance could be seen by some primordially existing or
created "fossil" charges with the property of moving through the Universe with
a fixed velocity.Comment: Extended versio
Minimal Mixing of Quarks and Leptons in the SU(3) Theory of Flavour
We argue that flavour mixing, both in the quark and lepton sector, follows
the minimal mixing pattern, according to which the whole of this mixing is
basically determined by the physical mass generation for the first family of
fermions. So, in the chiral symmetry limit when the masses of the lightest (
and ) quarks vanish, all the quark mixing angles vanish. This minimal
pattern is shown to fit extremely well the already established CKM matrix
elements and to give fairly distinctive predictions for the as yet poorly known
ones. Remarkably, together with generically small quark mixing, it also leads
to large neutrino mixing, provided that neutrino masses appear through the
ordinary ``see-saw'' mechanism. It is natural to think that this minimal
flavour mixing pattern presupposes some underlying family symmetry, treating
families of quarks and leptons in a special way. Indeed, we have found a local
chiral family symmetry model which leads, through its dominant
symmetry breaking vacuum configuration, to a natural realization of the
proposed minimal mechanism. It can also naturally generate the quark and lepton
mass hierarchies. Furthermore spontaneous CP violation is possible, leading to
a maximal CP violating phase , in the framework of the
MSSM extended by a high-scale chiral family symmetry.Comment: 52 pages, LaTex, no figures; some typos corrected; journal versio
On Emergent Gauge and Gravity Theories
We present some general approach to emergent gauge theories and consider in
significant detail the emergent tensor field gravity case. In essence, an
arbitrary local theory of a symmetric two-tensor field in
Minkowski spacetime is considered, in which the equations of motion are
required to be compatible with a nonlinear model type length-fixing
constraint leading to spontaneous Lorentz
invariance violation, SLIV ( is the proposed scale for SLIV). Allowing the
parameters in the Lagrangian to be adjusted so as to be consistent with this
constraint, the theory turns out to correspond to linearized general relativity
in the weak field approximation, while some of the massless tensor Goldstone
modes appearing through SLIV are naturally collected in the physical graviton.
The underlying diffeomophism invariance emerges as a necessary condition for
the tensor field not to be superfluously restricted in degrees of
freedom, apart from the constraint due to which the true vacuum in the theory
is chosen by SLIV. The emergent theory appears essentially nonlinear, when
expressed in terms of the pure Goldstone tensor modes and contains a plethora
of new Lorentz and violating couplings. However, these couplings do not
lead to physical Lorentz violation once this tensor field gravity is properly
extended to conventional general relativity.Comment: 10 pages, Invited talk given at the International Workshop "Low
dimensional physics and gauge principles" (21-29 September 2011,
Yerevan-Tbilisi), to appear in the Conference Proceedings (World Scientific,
2012
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