arXiv subjects

D. V. Nanopoulos

Publications and source records attributed to D. V. Nanopoulos.

At least 55 records · Page 3Linked to original sources

arXiv2003

WMAPing out Supersymmetric Dark Matter and Phenomenology

The recent WMAP data provide a rather restricted range of the Cold Dark Matter (CDM) density $ Ω_{CDM} h^2 $ of unprecedented accuracy. We combine these new data along with data from BNL E821 experiment measuring $ {(g_μ-2)}$, $ $the {$b\goes s γ$} branching ratio and the light Higgs boson mass bound from LEP, to update our analysis of the allowed boundaries in the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM). The prospects of measuring Supersymmetry at LHC look like a very safe bet, and the potential of discovering SUSY particles at a $ \sqrt{s} = 1.1 \mathrm{TeV} $ linear collider is enhanced considerably. The implications for Dark Matter direct searches are also discussed.

hep-ph↗

arXiv2003

Quantum-Gravity Analysis of Gamma-Ray Bursts using Wavelets

In some models of quantum gravity, space-time is thought to have a foamy structure with non-trivial optical properties. We probe the possibility that photons propagating in vacuum may exhibit a non-trivial refractive index, by analyzing the times of flight of radiation from gamma-ray bursters (GRBs) with known redshifts. We use a wavelet shrinkage procedure for noise removal and a wavelet `zoom' technique to define with high accuracy the timings of sharp transitions in GRB light curves, thereby optimizing the sensitivity of experimental probes of any energy dependence of the velocity of light. We apply these wavelet techniques to 64 ms and TTE data from BATSE, and also to OSSE data. A search for time lags between sharp transients in GRB light curves in different energy bands yields the lower limit $M \ge 6.9 \cdot 10^{15}$ GeV on the quantum-gravity scale in any model with a linear dependence of the velocity of light $~ E/M$. We also present a limit on any quadratic dependence.

astro-ph↗

arXiv2003

Surface plasmon resonance study of the actin-myosin sarcomeric complex and tubulin dimers

Biosensors based on the principle of surface plasmon resonance (SPR) detection were used to measure biomolecular interactions in sarcomeres and changes of the dielectric constant of tubulin samples with varying concentration. At SPR, photons of laser light efficiently excite surface plasmons propagating along a metal (gold) film. This resonance manifests itself as a sharp minimum in the reflection of the incident laser light and occurs at a characteristic angle. The dependence of the SPR angle on the dielectric permittivity of the sample medium adjacent to the gold film allows the monitoring of molecular interactions at the surface. We present results of measurements of cross-bridge attachment/detachment within intact mouse heart muscle sarcomeres and measurements on bovine tubulin molecules pertinent to cytoskeletal signal transduction models.

quant-ph↗

arXiv2003

Impact of Low-Energy Constraints on Lorentz Violation

We extend previous analyses of the violation of Lorentz invariance induced in a non-critical string model of quantum space-time foam, discussing the propagation of low-energy particles through a distribution of non-relativistic D-particles.We argue that nuclear and atomic physics experiments do not constitute sensitive probes of this approach to quantum gravity due to a difference in the dispersion relations for massive probes as compared to those for massless ones, predicted by the model.

gr-qc↗

arXiv2002

Universal Calabi-Yau Algebra: Classification and Enumeration of Fibrations

We apply a universal normal Calabi-Yau algebra to the construction and classification of compact complex $n$-dimensional spaces with SU(n) holonomy and their fibrations. This algebraic approach includes natural extensions of reflexive weight vectors to higher dimensions and a `dual' construction based on the Diophantine decomposition of invariant monomials. The latter provides recurrence formulae for the numbers of fibrations of Calabi-Yau spaces in arbitrary dimensions, which we exhibit explicitly for some Weierstrass and K3 examples.

hep-th↗

arXiv2002

Updating the constraints to CMSSM from cosmology and accelerator experiments

The recent data from E821 Brookhaven experiment in conjunction with a new determination of the hadronic vacuum polarization contribution to the anomalous magnetic moment of muon, put new bounds on the parameters of the Constrained Minimal Supersymmetric Standard Model. We study the impact this experimental information, along with the $b \goes s γ$ branching ratio and light Higgs boson mass bound from LEP, to constrain regions of the model which are consistent with the cosmological data. The effect of these to Dark Matter direct searches is also discussed.

hep-ph↗

arXiv2002

Intersecting Branes Flip SU(5)

Within a toroidal orbifold framework, we exhibit intersecting brane-world constructions of flipped SU(5) \times U(1) GUT models with various numbers of generations, other chiral matter representations and Higgs representations. We exhibit orientifold constructions with integer winding numbers that yield 8 or more conventional SU(5) generations, and orbifold constructions with fractional winding numbers that yield flipped SU(5) \times U(1) models with just 3 conventional generations. Some of these models have candidates for the 5 and {\bar 5} Higgs representations needed for electroweak symmetry breaking, but not for the 10 and {\bar 10} representations needed for GUT symmetry breaking. We have also derived models with complete GUT and electroweak Higgs sectors, but these have undesirable extra chiral matter.

hep-th↗

arXiv2002

Universal Calabi-Yau Algebra: Towards an Unification of Complex Geometry

We present a universal normal algebra suitable for constructing and classifying Calabi-Yau spaces in arbitrary dimensions. This algebraic approach includes natural extensions of reflexive weight vectors to higher dimensions, related to Batyrev's reflexive polyhedra, and their n-ary combinations. It also includes a `dual' construction based on the Diophantine decomposition of invariant monomials, which provides explicit recurrence formulae for the numbers of Calabi-Yau spaces in arbitrary dimensions with Weierstrass, K3, etc., fibrations. Our approach also yields simple algebraic relations between chains of Calabi-Yau spaces in different dimensions, and concrete visualizations of their singularities related to Cartan-Lie algebras. This Universal Calabi-Yau Algebra is a powerful tool for decyphering the Calabi-Yau genome in all dimensions.

hep-th↗

arXiv2002

Flipping SU(5) out of Trouble

Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of alpha_s, sin^2 theta_W, the lower limit on the lifetime for p to nubar K decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, accommodating the experimental values of alpha_s and sin^2 theta_W and other constraints, while yielding a p to e/mu+ pi0 lifetime beyond the present experimental limit but potentially accessible to a further round of experiments. We exemplify our analysis using a set of benchmark supersymmetric scenarios proposed recently in a constrained MSSM framework.

hep-ph↗

arXiv2002

Supersymmetric Dark Matter and Recent Experimental Constraints

In this talk we discuss the impact of recent experimental information, like the revised bound from E821 Brookhaven experiment on $g_μ-2$ and light Higgs boson mass bound from LEP, in delineating regions of the parameters of the Constrained Minimal Supersymmetric Standard Model which are consistent with the cosmological data. The effect of these to Dark Matter direct searches is also discussed.

hep-ph↗

arXiv2002

QED-Cavity model of microtubules implies dissipationless energy transfer and biological quantum teleportation

We refine a QED-cavity model of microtubules (MTs), proposed earlier by two of the authors (N.E.M. and D.V.N.), and suggest mechanisms for the formation of biomolecular mesoscopic coherent and/or entangled quantum states, which may avoid decoherence for times comparable to biological characteristic times. This refined model predicts dissipationless energy transfer along such "shielded" macromolecules at near room temperatures as well as quantum teleportation of states across MTs and perhaps neurons.

quant-ph↗

arXiv2001

Combining Supersymmetric Dark Matter with Recent Accelerator Data

In the framework of the Constrained Minimal Supersymmetric Standard Model we discuss the impact of the recent experimental information, especially from the E821 Brookhaven experiment on $g_μ-2$ along with the light Higgs boson mass bound from LEP, in delineating regions of the parameters which are consistent with cosmological data. The effect of these to the Dark Matter direct searches is also discussed.

hep-ph↗

arXiv2001

Lower Limits on Soft Supersymmetry-Breaking Scalar Masses

Working in the context of the CMSSM, we argue that phenomenological constraints now require the universal soft supersymmetry-breaking scalar mass m_0 be non-zero at the input GUT scale. This conclusion is primarily imposed by the LEP lower limit on the Higgs mass and the requirement that the lightest supersymmetric particle not be charged. We find that m_0 > 0 for all tan beta if mu < 0, and m_0 = 0 may be allowed for mu > 0 only when tan beta sim 8 and one allows an uncertainty of 3+ GeV in the theoretical calculation of the Higgs mass. Upper limits on flavour-changing neutral interactions in the MSSM squark sector allow substantial violations of non-universality in the m_0 values, even if their magnitudes are comparable to the lower limit we find in the CMSSM. Also, we show that our lower limit on m_0 at the GUT scale in the CMSSM is compatible with the no-scale boundary condition m_0 = 0 at the Planck scale.

hep-ph↗

arXiv2001

Non-Critical Liouville String Escapes Constraints on Generic Models of Quantum Gravity

It has recently been pointed out that generic models of quantum gravity must contend with severe phenomenological constraints imposed by gravitational Cerenkov radiation, neutrino oscillations and the cosmic microwave background radiation. We show how the non-critical Liouville-string model of quantum gravity we have proposed escapes these constraints. It gives energetic particles subluminal velocities, obviating the danger of gravitational Cerenkov radiation. The effect on neutrino propagation is naturally flavour-independent, obviating any impact on oscillation phenomenology. Deviations from the expected black-body spectrum and the effects of time delays and stochastic fluctuations in the propagation of cosmic microwave background photons are negligible, as are their effects on observable spectral lines from high-redshift astrophysical objects.

astro-ph↗

arXiv2001

Dark Matter Direct Searches and the Anomalous Magnetic Moment of Muon

In the framework of the Constrained Minimal Supersymmetric Standard Model (CMSSM) we discuss the impact of the recent experimental information, especially from E821 Brookhaven experiment on $g_μ-2$ along with the light Higgs boson mass bound from LEP, to the Dark Matter direct searches. Imposing these experimental bounds, the maximum value of the spin-independent neutralino-nucleon cross section turns out to be of the order of $10^{-8}$ pb for large values of $\tanβ$ and low $M_{1/2}, m_0$. The effect of the recent experimental bounds is to decrease the maximum value of the cross section by about an order of magnitude, demanding the analogous sensitivity from the direct Dark Matter detection experiments.

hep-ph↗

arXiv2001

\$tring Theory and an Accelerating Universe

An accelerating Universe can be accommodated naturally within non-critical string theory, in which scattering is described by a superscattering matrix \$ that does not factorize as a product of $S$- and $S^\dagger$-matrix elements and time evolution is described by a modified Liouville equation characteristic of open quantum-mechanical systems. We describe briefly alternative representations in terms of the stochastic Ito and Fokker-Planck equations. The link between the vacuum energy and the departure from criticality is stressed. We give an explicit example in which non-marginal \$tring couplings cause a departure from criticality, and the corresponding cosmological vacuum energy relaxes to zero à la quintessence.

hep-th↗

arXiv2001

Neutralino Dark Matter Elastic Scattering in a Flat and Accelerating Universe

In SUGRA inspired supersymmetric models with universal boundary conditions for the soft masses, the scalar cross section $σ_{scalar}$ for the elastic neutralino--nucleon scattering is in general several orders of magnitude below the sensitivity of current experiments. For large $\tan β$ and low $M_{1/2}, m_0$ values, the theoretically predicted $σ_{scalar}$ can approach the sensitivity of these experiments ($\approx 10^{-6} pb$) being at the same time in agreement with recent cosmological data, which impose severe restrictions on the CDM relic density, and with accelerator experiments which put lower bounds on sparticle and Higgs boson masses. Further improvement of the sensitivity of DAMA and CDMS experiments will probe the large $\tan β$ region of the parameter space in the vicinity of the boundaries of the parameter space allowed by chargino and Higgs searches.

hep-ph↗

arXiv2001

Phenomenology of Non-Abelian Flat Directions in a Minimal Superstring Standard Model

Recently, we presented the first non-Abelian flat directions that produce from a heterotic string model solely the three-generation MSSM states as the massless spectrum in the observable sector of the low energy effective field theory. In this paper we continue to develop the systematic techniques for the analysis of nonrenormalizable superpotential terms and non-Abelian flat direction in realistic string models. Some of our non-Abelian directions were F-flat to all finite orders in the superpotential. We study for the same string model the varying phenomenologies resulting from a large set of such all-order flat directions. We focus on the quark, charged lepton, and Higgs doublet mass matrices resulting for our phenomenologically superior non-Abelian flat direction. We review and apply a string-related method for generating large mass hierarchies between MSSM generations, first discussed in string-derived flipped SU(5) models, when all generational mass terms are of renormalizable or very low non-renormalizable order.

hep-ph↗