746 research outputs found
Equivalence Theorem and Probing the Electroweak Symmetry Breaking Sector
We examine the Lorentz non-invariance ambiguity in longitudinal weak-boson
scatterings and the precise conditions for the validity of the Equivalence
Theorem (ET). {\it Safe} Lorentz frames for applying the ET are defined, and
the intrinsic connection between the longitudinal weak-boson scatterings and
probing the symmetry breaking sector is analyzed. A universal precise
formulation of the ET is presented for both the Standard Model and the Chiral
Lagrangian formulated Electro-Weak Theories. It is shown that in electroweak
theories with strongly interacting symmetry breaking sector, the longitudinal
weak-boson scattering amplitude {\it under proper conditions} can be replaced
by the corresponding Goldstone-boson scattering amplitude in which all the
internal weak-boson lines and fermion loops are ignored.Comment: 20 pages, in LaTeX, to appear in Phys. Rev. D (1995). A few minor
corrections were made to clarify our viewpoint of the Equivalence Theorem and
compare our conclusion with those in the literatur
Duality cascades and duality walls
We recast the phenomenon of duality cascades in terms of the Cartan matrix
associated to the quiver gauge theories appearing in the cascade. In this
language, Seiberg dualities for the different gauge factors correspond to Weyl
reflections. We argue that the UV behavior of different duality cascades
depends markedly on whether the Cartan matrix is affine ADE or not. In
particular, we find examples of duality cascades that can't be continued after
a finite energy scale, reaching a "duality wall", in terminology due to M.
Strassler. For these duality cascades, we suggest the existence of a UV
completion in terms of a little string theory.Comment: harvmac, 24 pages, 4 figures. v2: references added. v3: reference
adde
Strong tree level unitarity violations in the extra dimensional Standard Model with scalars in the bulk
We show how the tree level unitarity violations of compactified extra
dimensional extensions of the Standard Model become much stronger when the
scalar sector is included in the bulk. This effect occurs when the couplings
are not suppressed for larger Kaluza-Klein levels, and could have relevant
consequences for the phenomenology of the next generation of colliders. We also
introduce a simple and generic formalism to obtain unitarity bounds for finite
energies, taking into account coupled channels including the towers of
Kaluza-Klein excitations.Comment: Version to appear in Phys. Rev. D Typos corrected and remarks added
to clarify figure
A-D-E Quivers and Baryonic Operators
We study baryonic operators of the gauge theory on multiple D3-branes at the
tip of the conifold orbifolded by a discrete subgroup Gamma of SU(2). The
string theory analysis predicts that the number and the order of the fixed
points of Gamma acting on S^2 are directly reflected in the spectrum of
baryonic operators on the corresponding quiver gauge theory constructed from
two Dynkin diagrams of the corresponding type. We confirm the prediction by
developing techniques to enumerate baryonic operators of the quiver gauge
theory which includes the gauge groups with different ranks. We also find that
the Seiberg dualities act on the baryonic operators in a non-Abelian fashion.Comment: 46 pages, 17 figures; v2: minor corrections, note added in section 1,
references adde
Bi-Large Neutrino Mixing See-Saw Mass Matrix with Texture Zeros and Leptogenesis
We study constraints on neutrino properties from texture zeros in bi-large
mixing See-Saw mass matrix and also from leptogenesis. Texture zeros may occur
in the light (class a)) or in the heavy (class b)) neutrino mass matrices. Each
of these two classes has 5 different forms which can produce non-trivial three
generation mixing with at least one texture zero. We find that two types of
texture zero mass matrices in both class a) and class b) can be consistent with
present data on neutrino masses, mixing and produce the observed baryon
asymmetry of the universe. None of the neutrinos can have zero masses with the
lightest of the light neutrinos having a mass larger than about 0.039 eV for
class a) and 0.002 eV for class b). In these models although CKM CP violating
phase vanishes, non-zero Majorana phases, however, can exist and play an
important role in producing the observed baryon asymmetry in our universe
through leptogenesis mechanism. The requirement of producing the observed
baryon asymmetry can further distinguish different models and also restrict the
See-Saw scale to be in the range GeV.Comment: 21 pages, 7 figures revised version, some references added, to be
submitted to PR
Vanishing Effective Mass of the Neutrinoless Double Beta Decay?
We stress that massive neutrinos may be Majorana particles even if the
effective mass of the neutrinoless double beta decay m_ee vanishes. We show
that current neutrino oscillation data do allow m_ee = 0 to hold, if the
Majorana CP-violating phases lie in two specific regions. Strong constraints on
three neutrino masses can then be obtained. We find that the neutrino mass
spectrum performs a normal hierarchy: m_1 < m_2 < m_3. A possible texture of
the neutrino mass matrix is also illustrated under the m_ee = 0 condition.Comment: RevTex 9 pages (2 PS figures included). More discussions and
references added. Results partly changed. To appear in Phys. Rev.
Counting BPS Operators in Gauge Theories: Quivers, Syzygies and Plethystics
We develop a systematic and efficient method of counting single-trace and
multi-trace BPS operators with two supercharges, for world-volume gauge
theories of D-brane probes for both and finite . The
techniques are applicable to generic singularities, orbifold, toric, non-toric,
complete intersections, et cetera, even to geometries whose precise field
theory duals are not yet known. The so-called ``Plethystic Exponential''
provides a simple bridge between (1) the defining equation of the Calabi-Yau,
(2) the generating function of single-trace BPS operators and (3) the
generating function of multi-trace operators. Mathematically, fascinating and
intricate inter-relations between gauge theory, algebraic geometry,
combinatorics and number theory exhibit themselves in the form of plethystics
and syzygies.Comment: 59+1 pages, 7 Figure
Phase diagram for a class of spin-half Heisenberg models interpolating between the square-lattice, the triangular-lattice and the linear chain limits
We study the spin-half Heisenberg models on an anisotropic two-dimensional
lattice which interpolates between the square-lattice at one end, a set of
decoupled spin-chains on the other end, and the triangular-lattice Heisenberg
model in between. By series expansions around two different dimer ground states
and around various commensurate and incommensurate magnetically ordered states,
we establish the phase diagram for this model of a frustrated antiferromagnet.
We find a particularly rich phase diagram due to the interplay of magnetic
frustration, quantum fluctuations and varying dimensionality. There is a large
region of the usual 2-sublattice Ne\'el phase, a 3-sublattice phase for the
triangular-lattice model, a region of incommensurate magnetic order around the
triangular-lattice model, and regions in parameter space where there is no
magnetic order. We find that the incommensurate ordering wavevector is in
general altered from its classical value by quantum fluctuations. The regime of
weakly coupled chains is particularly interesting and appears to be nearly
critical.Comment: RevTeX, 15 figure
Heavy-Higgs Lifetime at Two Loops
The Standard-Model Higgs boson with mass decays almost
exclusively to pairs of and bosons. We calculate the dominant two-loop
corrections of to the partial widths of these decays. In
the on-mass-shell renormalization scheme, the correction factor is found to be
, where the second term is the
one-loop correction. We give full analytic results for all divergent two-loop
Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to
high precision using numerical techniques. We find agreement with a previous
numerical analysis. The above correction factor is also in line with a recent
lattice calculation.Comment: 26 pages, 6 postscript figures. The complete paper including figures
is also available via WWW at
http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-247-96.ps.g
Shear-induced dynamics of polymeric globules at adsorbing homogeneous and inhomogeneous surfaces
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