94 research outputs found
Gauged B-L unification and cosmology
We discuss some cosmological implications of low energy gauged B-L symmetry
with and without supersymmetry. Generic possibility of leptogenesis from a
domain wall driven first order phase transition is shown to be a characteristic
of such models.Comment: 6 pages. Talk given at IWTHEP 2007, IIT Roorke
Invisibly decaying Higgs boson in the Littlest Higgs model with T-parity
We show that there are regions in the parameter space of the Littlest Higgs
model with T-parity, allowed by electroweak precision data, where the Higgs
boson can decay invisibly into a pair of heavy photons A_H with a substantial
branching ratio. For a symmetry breaking scale f in the range 450-600 GeV, the
BR(H -> A_H A_H) can be up to 95% for an intermediate mass Higgs, and from 20%
down to a few percents for a Higgs boson of mass 200 GeV or above. The total
decay width of the Higgs boson can thereby be enhanced by an order of magnitude
compared to the Standard Model for Higgs masses around 130 GeV.Comment: 4 pages, 2 figures, Latex (stylefiles included); Talk presented by
A.N. at the International Workshop on Theoretical High Energy Physics (IWTHEP
2007), Roorkee, India, 15-20 March 2007, to appear in the proceeding
Supersymmetry of Noncompact MQCD-like Membrane Instantons and Heat Kernel Asymptotics
We perform a heat kernel asymptotics analysis of the nonperturbative
superpotential obtained from wrapping of an M2-brane around a supersymmetric
noncompact three-fold embedded in a (noncompact) G_2-manifold as obtained in
[1], the three-fold being the one relevant to domain walls in Witten's MQCD
[2], in the limit of small "zeta", a complex constant that appears in the
Riemann surfaces relevant to defining the boundary conditions for the domain
wall in MQCD. The MQCD-like configuration is interpretable, for small but
non-zero zeta as a noncompact/"large" open membrane instanton, and for
vanishing zeta, as the type IIA D0-brane (for vanishing M-theory cicle radius).
We find that the eta-function Seeley de-Witt coefficients vanish, and we get a
perfect match between the zeta-function Seeley de-Witt coefficients (up to
terms quadratic in zeta) between the Dirac-type operator and one of the two
Laplace-type operators figuring in the superpotential. This is an extremely
strong signature of residual supersymmetry for the nonperturbative
configurations in M-theory considered in this work.Comment: 21 pages, LaTeX; v3: several clarifying remarks added, to appear in
JHE
"Big" Divisor D3/D7 Swiss Cheese Phenomenology
We review progress made over the past couple of years in the field of Swiss
Cheese Phenomenology involving a mobile space-time filling D3-brane and
stack(s) of fluxed D7-branes wrapping the "big" (as opposed to the "small")
divisor in (the orientifold of a) Swiss-Cheese Calabi-Yau. The topics reviewed
include reconciliation of large volume cosmology and phenomenology, evaluation
of soft supersymmetry breaking parameters, one-loop RG-flow equations'
solutions for scalar masses, obtaining fermionic (possibly first two
generations' quarks/leptons) mass scales in the O(MeV-GeV)-regime as well as
(first two generations') neutrino masses (and their one-loop RG flow) of around
an eV. The heavy sparticles and the light fermions indicate the possibility of
"split SUSY" large volume scenario.Comment: Invited review for MPLA, 14 pages, LaTe
MQCD, ('Barely') G_2 Manifolds and (Orientifold of) a Compact Calabi-Yau
We begin with a discussion on two apparently disconnected topics - one
related to nonperturbative superpotential generated from wrapping an M2-brane
around a supersymmetric three cycle embedded in a G_2-manifold evaluated by the
path-integral inside a path-integral approach of [1], and the other centered
around the compact Calabi-Yau CY_3(3,243) expressed as a blow-up of a degree-24
Fermat hypersurface in WCP^4[1,1,2,8,12]. For the former, we compare the
results with the ones of Witten on heterotic world-sheet instantons [2]. The
subtopics covered in the latter include an N=1 triality between Heterotic, M-
and F-theories, evaluation of RP^2-instanton superpotential, Picard-Fuchs
equation for the mirror Landau-Ginsburg model corresponding to CY_3(3,243),
D=11 supergravity corresponding to M-theory compactified on a `barely' G_2
manifold involving CY_3(3,243) and a conjecture related to the action of
antiholomorphic involution on period integrals. We then show an indirect
connection between the two topics by showing a connection between each one of
the two and Witten's MQCD [3]. As an aside, we show that in the limit of
vanishing "\zeta", a complex constant that appears in the Riemann surfaces
relevant to definining the boundary conditions for the domain wall in MQCD, the
infinite series of [4] used to represent a suitable embedding of a
supersymmetric 3-cycle in a G_2-mannifold, can be summed.Comment: 37 pages, LaTex; PARTLY based on talks given at ``Seventh Workshop on
QCD" [session on "Strings, Branes and (De-)Construction"], Jan 6-10, 2003, La
Cittadelle, Villefranche-sur-Mer, France; Fourth Workshop on ``Gauge Fields
and Strings", Feb 25-Mar 1, 2003, Jena, Germany; ``XII Oporto Meeting on
Geometry, Topology and Strings", July 17-20, 2003, Oporto, Portugal; "SQS03"
- International Workshop on "Supersymmetries and Quantum Symmetries', July
24-29, 2003, JINR, Dubna, Russia; poster presented at ``XIV International
Congress on Mathematical Physics", July 28-Aug 2, 2003, Lisbon, Portuga
Background Independent Quantum Mechanics, Metric of Quantum States, and Gravity: A Comprehensive Perspective
This paper presents a comprehensive perspective of the metric of quantum
states with a focus on the background independent metric structures. We also
explore the possibilities of geometrical formulations of quantum mechanics
beyond the quantum state space and Kahler manifold. The metric of quantum
states in the classical configuration space with the pseudo-Riemannian
signature and its possible applications are explored. On contrary to the common
perception that a metric for quantum state can yield a natural metric in the
configuration space with the limit when Planck constant vanishes, we obtain the
metric of quantum states in the configuration space without imposing this
limiting condition. Here, Planck constant is absorbed in the quantity like Bohr
radii. While exploring the metric structure associated with Hydrogen like atom,
we witness another interesting finding that the invariant lengths appear in the
multiple of Bohr radii.Comment: 25 Pages;journal reference added:Published in- Int. J. Theor. Phys.
46 (2007) 3216-3229. References revise
New Insights into Properties of Large-N Holographic Thermal QCD at Finite Gauge Coupling at (the Non-Conformal/Next-to) Leading Order in N
In the context of [1]'s string theoretic dual of large-N thermal QCD-like
theories at finite gauge/string coupling (as part of the `MQGP' limit of [2]),
we discuss the following. First, up to LO in N, using the results of [3], we
show that the local T^3 of [2] is the T^2-invariant sLag of [3] in a resolved
conifold. This, together with the results of [4], shows that for a
(predominantly resolved or deformed) resolved warped deformed conifold, the
local T^3 of [2] in the MQGP limit, is the T^2-invariant sLag of [3] justifying
the construction of the delocalized SYZ type IIA mirror of the type IIB
background of [1]. Then, using the prescription of [5], we obtain the
temperature dependence of the thermal (and electrical) conductivity working up
to leading order in N (the number of D3-branes), and upon comparison with [6]
show that the results mimic a 1+1-dimensional Luttinger liquid with impurities.
Further, including sub-leading non-conformal terms in the metric determined by
M (the number of fractional D-branes = the number of colors = 3 in the IR after
the end of a Seiberg duality cascade), by looking at respectively the scalar,
vector and tensor modes of metric perturbations and using [7]'s prescription of
constructing appropriate gauge-invariant perturbations, we obtain respectively
the speed of sound, the diffusion constant and the shear viscosity \eta (and
\eta/s) including the non-conformal O((g_s M^2) (g_s N_f)/N<<1)-corrections,
N_f being the number of flavor D7-branes.Comment: 1+75 pages, LaTeX; Some corrections in Tc-related calculations,
results unchange
Orientifolds, Unoriented Instantons and Localization
We consider world-sheet instanton effects in N=1 string orientifolds of
noncompact toric Calabi-Yau threefolds. We show that unoriented closed string
topological amplitudes can be exactly computed using localization techniques
for holomorphic maps with involution. Our results are in precise agreement with
mirror symmetry and large N duality predictions.Comment: 25 pages, 10 figures, published version; v4: typos correcte
On 'Light' Fermions and Proton Stability in 'Big Divisor' D3/D7 Swiss Cheese Phenomenology
Building up on our earlier work [1,2], we show the possibility of generating
"light" fermion mass scales of MeV-GeV range (possibly related to first two
generations of quarks/leptons) as well as eV (possibly related to first two
generations of neutrinos) in type IIB string theory compactified on
Swiss-Cheese orientifolds in the presence of a mobile space-time filling
D3-$brane restricted to (in principle) stacks of fluxed D7-branes wrapping the
"big" divisor \Sigma_B. This part of the paper is an expanded version of the
latter half of section 3 of a published short invited review [3] written up by
one of the authors [AM]. Further, we also show that there are no SUSY GUT-type
dimension-five operators corresponding to proton decay, as well as estimate the
proton lifetime from a SUSY GUT-type four-fermion dimension-six operator to be
10^{61} years. Based on GLSM calculations in [1] for obtaining the geometric
Kaehler potential for the "big divisor", using further the Donaldson's
algorithm, we also briefly discuss in the first of the two appendices,
obtaining a metric for the Swiss-Cheese Calabi-Yau used, that becomes Ricci
flat in the large volume limit.Comment: v2: 1+25 pages, Title modified and text thoroughly expanded including
a brief discussion on obtaining Ricci-flat Swiss Cheese Calabi-Yau metrics
using the Donaldson's algorithm, references added, to appear in EPJ
The PP2A inhibitor SET regulates natural killer cell IFN-γ production
Monokines (i.e., interleukin [IL]-12, -18, and -15) induce natural killer (NK) cells to produce interferon-γ (IFN-γ), which is a critical factor for immune surveillance of cancer and monocyte clearance of infection. We show that SET, which is a potent inhibitor of protein phosphatase type 2A (PP2A) activity, is highly expressed in human CD56bright NK cells, which produce more IFN-γ than CD56dim NK cells. SET was up-regulated upon monokine stimulation of primary human NK cells. Furthermore, ectopic overexpression of SET significantly enhanced IFN-γ gene expression in monokine-stimulated NK cells. In contrast, RNAi-mediated suppression of SET expression renders NK cells inefficient in producing high levels of IFN-γ in response to monokine costimulation. Mechanistically, suppression of PP2A activity by SET is important for IFN-γ gene expression in NK cells. In fact, treatment of primary human NK cells with the PP2A activator 1,9-dideoxy-forskolin, as well as administration of the drug to C57BL/6 mice, significantly reduced NK-dependent IFN-γ production in response to monokine treatment. Further, SET knockdown or pharmacologic activation of PP2A diminished extracellular signal-regulated kinase 1/2, p65RelA, signal transducer and activator of transduction 4 (STAT4), and STAT5 activity in monokine-stimulated NK cells, potentially contributing to the reduction in IFN-γ gene expression. Thus, SET expression is essential for suppressing PP2A phosphatase activity that would otherwise limit NK cell antitumoral and/or antiinflammatory functions by impairing NK cell production of IFN-γ
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