D.V. Nanopoulos's research while affiliated with Texas A&M University and other places

Publications (464)

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The first and second swampland conjectures (FSC & SSC) are substantially modified in noncritical string cosmology, in which cosmic time is identified with the timelike Liouville mode of the supercritical string. In this scenario the Friedmann equation receives additional contributions due to the noncriticality of the string. These are potentially i...
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Building upon our previous work on two-dimensional stringy black holes and its extension to spherically-symmetric four-dimensional stringy black holes, we show how the latter retain information. A key r\^ole is played by an infinite-dimensional $W_\infty$ symmetry that preserves the area of an isolated black-hole horizon and hence its entropy. The...
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We point out that the electroweak fine-tuning problem in the supersymmetric Standard Models (SSMs) is mainly due to the high energy definition of the fine-tuning measure. We propose super-natural supersymmetry which has an order one high energy fine-tuning measure automatically. The key point is that all the mass parameters in the SSMs arise from a...
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With the Higgs boson mass around 125 GeV and the LHC supersymmetry search constraints, we revisit a three-family Pati-Salam model from intersecting D6-branes in Type IIA string theory on the T 6/(ℤ2 × ℤ2) orientifold which has a realistic phenomenology. We systematically scan the parameter space for μ < 0 and μ > 0, and find that the gravitino mass...
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We show that an exact solution of two-dimensional dilaton gravity with matter discovered previously exhibits an irreversible temporal flow towards flat space with a vanishing cosmological constant. This time flow is induced by the back reaction of matter on the space–time geometry. We demonstrate that the system is not in equilibrium if the cosmolo...
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In order to produce a low-energy effective field theory from a string model, it is necessary to specify a vacuum state. In order that this vacuum be supersymmetric, it is well known that all field expectation values must be along so-called flat directions, leaving the F- and D-terms of the scalar potential to be zero. The situation becomes particul...
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We consider the quantum cosmology of a D-dimensional Universe using the point-like field theory effective action of closed bosonic strings. We find that in order to apply the Hartle-Hawking boundary condition, the Universe must have a product topology (like R × Sn × Sm). This rules out four-dimensional theories (unless they are supplemented by extr...
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We discuss possible quantum mechanical aspects of MicroTubules (MT), based on recent developments in quantum physics. We focus on potential mechanisms for "energy-loss-free" transport along the microtubules, which could be considered as realizations of Fröhlich's ideas on the rôle of solitons for superconductivity and/or biological matter. In parti...
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We consider the experimental predictions of two one-parameter no-scale SU(5)×U(1) supergravity models with string-inspired moduli and dilaton seeds of supersymmetry breaking. These predictions have been considerably sharpened with the new information on the top-quark mass from the Tevatron, and the actual measurement of the B(b→sγ) branching ratio...
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We argue that CPT is in general violated in a non-quantum-mechanical way in the effective low-energy theory derived from noncritical string theory, in which pure states evolve into mixed states in general. It is known that such a dynamical framework violates the strong form of CPT invariance. We relate CPT violation in the effective low-energy theo...
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Microtubule (MT) networks, subneural paracrystalline cytoskeletal structures, seem to play a fundamental role in the neurons. We cast here the complicated MT dynamics in the form of a (1+1)-dimensional noncritical string theory, thus enabling us to provide a consistent quantum treatment of MTs, including enviromental friction effects. We suggest, t...
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We explore the postulates of string no-scale supergravity in the context of free-fermionic string models. The requirements of vanishing vacuum energy, flat directions of the scalar potential, and stable no-scale mechanism impose strong restrictions on possible string no-scale models, which must possess only two or three moduli, and a constrained ma...
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We first review the interpretation of world sheet defects as D branes described by a critical theory in 11 dimensions, that we interpret as M theory. We then show that D-brane recoil induces dynamically an anti-de Sitter (AdS) space–time background, with criticality restored by a twelfth timelike dimension described by a Liouville field. Local phys...
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Three family SU(3)C×SU(2)L×U(1)Y string models in several constructions generically possess two features: (i) an extra local anomalous U(1)A and (ii) numerous (often fractionally charged) exotic particles beyond those in the minimal supersymmetric model (MSSM). Recently, we demonstrated that the observable sector effective field theory of such a fr...
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In this review we critically discuss constraints on minimal supersymmetric models of particle physics as implied by the recent astrophysical observations of WMAP satellite experiment. Although the prospects of detecting supersymmetry increase dramatically, at least within the context of the minimal models, and 90% of the available parameter space c...
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We construct supersymmetric Pati–Salam flux vacua in AdS from intersecting D6-branes on T6/(ℤ2 × ℤ′2). The models constructed have three generations of MSSM matter plus right-handed neutrinos. Because the cycles wrapped by the D-branes are rigid there are no extra massless fields in the adjoint representation, arising as open-string moduli. However...
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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 D...
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We discuss cosmological baryogenesis in phenomenological low-energy models inspired by the superstring which have an unobservably long baryon lifetime. The Affleck-Dine mechanism of baryogenesis in a cold (≲104GeV) universe is shown to be feasible, with a large baryon density being produced by the decays of large expectation values for squark and s...
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We compile phenomenological constraints on the minimal low-energy effective theory which can be obtained from the superstring by Calabi-Yau compactification. Mixing with the single additional neutral gauge boson in this model reduces the mass of the conventional Z0, Field vacuum expectation values are constrained by the experimental upper bound on...
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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 mon...
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In supercritical string cosmology (SSC), a time-dependent dilaton leads to a smoothly evolving dark energy and modifies the regions of the mSUGRA parameter space where the observed value of the dark matter relic density may be obtained. In particular, the dilaton dilutes the supersymmetric dark matter density (of neutralinos) by a factor and conseq...
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We consider a string-inspired no-scale SU(5) × U(1) supergravity model. In this model there is a negative contribution to the vacuum energy, which may be suitably canceled by a positive contribution typically present in string theory. One may then end up with a vacuum energy which brings many cosmological observations into better agreement with the...
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In SUGRA inspired supersymmetric models with universal boundary conditions for the soft masses, the scalar cross-section σscalar 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 M1/2, m0 values, the theoretically predicted σscalar can approa...
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We propose a supergravity model that contains elements recently shown to arise in the strongly-coupled limit of the E8 × E8 heterotic string (M-theory), including a no-scale-like Kähler potential, the identification of the string scale with the gauge coupling unification scale, and the onset of supersymmetry breaking at an intermediate scale determ...
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No-scale supergravity is a framework where it is possible to naturally explain radiative electroweak symmetry breaking and correlate it with the effective SUSY breaking scale. Many string compactifications have a classical no-scale structure, resulting in a one-parameter model (OPM) for the supersymmetry breaking soft terms, which results in a high...
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We propose a new cosmological model with a time-dependent cosmological constant (Λ∝1/t2), which starting at the Planck time as , evolves to the present-day allowed value of . This scenario is supported by noncritical string theory considerations. We compute the age of the Universe and the time dependence of the scale factor in this model, and find...
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Within a Liouville approach to noncritical string theory, we argue for a nontrivial commutation relation between space and time observables, leading to a nonzero space–time uncertainty relation δx δt>0, which vanishes in the limit of weak string coupling.
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We examine supersymmetry breaking in string-inspired models through gaugino condensation in the hidden sector. With the physically sensible assumption that observable supersymmetry breaking effects turn off above the gaugino condensation scale (Λh), we derive a realistic range for the scale where supersymmetry breaks (1012 GeV<ΛSUSY= Λh<1016 GeV) w...
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We revisit the no-scale mechanism in the context of the simplest no-scale supergravity extension of the standard model. This model has the usual four-dimensional parameter space plus an additional parameter ξ3/2≡m3/2/m1/2. We show how predictions of the model may be extracted over the whole parameter space. A necessary condition for the potential t...
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Recently, by studying exact flat directions of non-Abelian singlet fields, we demonstrated the existence of free fermionic heterotic-string models in which the SU(3)C×SU(2)L×U(1)Y-charged matter spectrum reduces to that of the MSSM in the effective field theory. In this letter we generalize the analysis to include vevs of non-Abelian fields. We fin...
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We demonstrate the existence of an extra nonanomalous U(1) gauge symmetry in a three-generation Pati-Salam model constructed with intersecting D6-branes in Type IIA string theory on a T^6/(Z_2 \times Z_2) orientifold. This extra U(1) forbids all dimension-4, 5, and 6 operators which mediate proton decay in the MSSM. Moreover, this results in the ef...
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In supercritical string cosmology (SSC) , a time-dependent dilaton leads to a smoothly evolving dark energy and modifies the regions of the mSUGRA parameter space where the observed value of the dark matter relic density may be obtained. In particular, the dilaton dilutes the supersymmetric dark matter density (of neutralinos) by a factor 0 ( 10) a...
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Recently, the CDMS experiment has reported the possible first direct-detection of dark matter. We update the direct-detection constraints for neutralino dark matter arising in a realistic string model constructed from intersecting D6-branes taking into account the recent data from the CDMS collaboration. We find that there are well-defined regions...
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In models where supersymmetry-breaking is dominated by the Kahler moduli and/or the universal dilaton, the B-parameter at the unification scale should be consistent with the value of tan(beta) at the electroweak scale determined by minimization of the Higgs potential triggering REWSB. We study such models employing a self-consistent determination o...
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We survey the low-energy supersymmetry phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in Type IIA string theory on the T^6/(Z_2 x Z_2) orientifold which possesses many of the phenomenological properties desired in string model-building. In the model, there is no exotic matter in the low-energy spectrum, the...
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We discuss the phenomenology of Supercritical String Cosmology (SSC) in the context of Dark Matter constraints on supersymmetric particle physics models at LHC. We also link our results with recent findings of the MAGIC, H.E.S.S. and Fermi Telescopes on delayed arrival of highly energetic photons from the distant Galaxies and GRBs. The link is prov...
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We have used a stringy model of quantum space–time foam to suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on γ-ray energy: η−1∼Eγ/MQG1, where MQG is some mass scale typical of quantum gravity that may be ∼1018 GeV: see [J. Ellis, N.E. Mavromatos, D.V. Nanopoulos, Phys. Lett. B 665 (2008) 412] and references th...
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We use the timing of photons observed by the MAGIC gamma-ray telescope during a flare of the active galaxy Markarian 501 to probe a vacuum refractive index ~ 1-(E/M_QGn)^n, n = 1,2, that might be induced by quantum gravity. The peaking of the flare is found to maximize for quantum-gravity mass scales M_QG1 ~ 0.4x10^18 GeV or M_QG2 ~ 0.6x10^11 GeV,...
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We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index ≃1+n(E/MQGn), n=1,2. Parametrizing the delay between γ-rays of different energies as Δt=±τlE or Δt...
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We discuss corrections to the Yukawa matrices of the Standard Model (SM) fermions in intersecting D-brane models due to four-point interactions. Recently, an intersecting D-brane model has been found where it is possible to obtain correct masses and mixings for all quarks as well as the tau lepton. However, the masses for the first two charged lept...
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We investigate the minimal supergravity (mSUGRA) signals at the LHC in the context of supercritical string cosmology (SSC). In this theory, the presence of a time dependent dilaton provides us with a smoothly evolving dark energy and modifies the dark matter allowed region of the mSUGRA model with standard cosmology. Such a dilaton dilutes the supe...
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It has been suggested that energetic photons propagating in vacuo should experience a non-trivial refractive index due to the foamy structure of space–time induced by quantum-gravitational fluctuations. The sensitivity of recent astrophysical observations, particularly of AGN Mk501 by the MAGIC Collaboration, approaches the Planck scale for a refra...
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We study the possible phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in type IIA string theory on the T6/(Z2×Z2) orientifold with some desirable semirealistic features. In the model, tree-level gauge-coupling unification is achieved automatically at the string scale, and the gauge symmetry may be broken to...
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We correct the fitting formula used [J.R. Ellis, N.E. Mavromatos, D.V. Nanopoulos, A.S. Sakharov, E.K.G. Sarkisyan, Astropart. Phys. 25 (2006) 402. Available from: <astro-ph/0510172>] to obtain a robust limit on a violation of Lorentz invariance that depends linearly on the photon energy. The correction leads to a slight increase of the limit on th...
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We study the possible phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in Type IIA string theory on the T6/(Z2 × Z2) orientifold with some desirable semi-realistic features. In the model, tree-level gauge coupling unification is achieved automatically at the string scale, and the gauge symmetry may be broken...
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We correct the fitting formula used in refs. [1,2] to obtain a robust limit on a violation of Lorentz invariance that depends linearly on the photon energy. The correction leads to a slight increase of the limit on the scale of the violation, to M > 1.4 x 10^{16} GeV.
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We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index \simeq 1 + (E/M_{QGn})^n, n = 1,2. Parametrizing the delay between gamma-rays of different energie...
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We construct an MSSM-like model via Pati Salam from intersecting D-branes in type IIA theory on the Z×Z2‧ orientifold where the D-branes wrap rigid 3-cycles. Because the 3-cycles are rigid, there are no extra massless fields in the adjoint representation, arising as open-string moduli. The presence of these unobserved fields would create difficulti...
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We show that Supercritical-String-Cosmology (SSC) off-equilibrium and time-dependent-dilaton effects lead to a smoothly evolving dark energy for the last 10 billion years in concordance with all presently available astrophysical data. Such effects dilute by a factor O(10) the supersymmetric dark matter density (neutralinos), relaxing severe WMAP 1,...
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We construct an MSSM-like model from intersecting D-branes in Type IIA theory on the Z 2 × Z ′ 2 orientifold where the D-branes wrap rigid 3-cycles. Because the 3-cycles are rigid, there are no extra massless fields in the adjoint representation, arising as open-string moduli. The presence of these unobserved fields would create difficulties with a...
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We calculate the spectra of ultrahigh-energy cosmic rays (UHECRs) in an explicit top-down model based on the decays of metastable neutral “crypton” states in a flipped SU(5) string model. For each of the eight specific 10th-order superpotential operators that might dominate crypton decays, we calculate the spectra of both protons and photons, using...
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In this work we derive the modifications to the Boltzmann equation governing the cosmic evolution of relic abundances induced by dilaton dissipative-source and non-critical-string terms in dilaton-driven non-equilibrium string Cosmologies. We also discuss briefly the most important phenomenological consequences, including modifications of the const...
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We consider solutions of the cosmological equations pertaining to a dissipative, dilaton-driven off-equilibrium Liouville cosmological model, which may describe the effective field theoretic limit of a non-critical string model of the Universe. The non-criticality may be the result of an early-era catastrophic cosmic event, such as a big-bang, bran...
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Impedance spectroscopy is a technique that reveals information, such as macromolecular charges and related properties, about protein suspensions and other materials. Here we report on impedance measurements over the frequency range 1 Hz - 1 MHz of alpha-beta tubulin heterodimers suspended in a buffer. These and other polyelectrolyte suspensions sho...
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We construct flipped SU(5) GUT models as type IIB flux vacua on Z2×Z2 orientifolds. Turning on supergravity self-dual NSNS and RR three-form fluxes fixes the toroidal complex structure moduli and the dilaton. We give a specific example of a three-generation flipped SU(5) model with a complete Higgs sector where supersymmetry is softly broken by the...
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We construct an N=1 supersymmetric three-family flipped SU(5) model from type IIA orientifolds on T6/(Z2×Z2) with D6-branes intersecting at general angles. The model is constrained by the requirement that Ramond–Ramond tadpoles cancel, the supersymmetry conditions, and that the gauge boson coupled to the UX(1) factor does not get a string-scale mas...
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In the context of a cosmological string model describing the propagation of strings in a time-dependent Robertson Walker background space time, we show that the asymptotic acceleration of the Universe can be identified with the square of the string coupling. This allows for a direct measurement of the ten-dimensional string coupling using cosmologi...
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We construct an N=1 supersymmetric three-family flipped SU(5) model from type IIA orientifolds on T6/(Z2×Z2) with D6-branes intersecting at general angles. The spectrum contains a complete grand unified and electroweak Higgs sector. In addition, it contains extra exotic matter both in bi-fundamental and vector-like representations as well as two co...
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We present an improved partial wave analysis of the dominant lightest supersymmetric particle (LSP) annihilation channel to a fermion-antifermion pair which avoids the nonrelativistic expansion being therefore applicable near thresholds and poles. The method we develop allows for contributions of any partial wave in the total angular momentum J in...
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Recent cosmological observations of unprecented accuracy, by WMAP in particular, have established a `Standard Model' of cosmology, just as LEP established the Standard Model of particle physics. Both Standard Models raise open questions whose answers are likely to be linked. The most fundamental problems in both particle physics and cosmology will...
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We present an improved partial wave analysis of the dominant LSP annihilation channel to a fermion-antifermion pair which avoids the non-relativistic expansion being therefore applicable near thresholds and poles. The method we develop allows of contributions of any partial wave in the total angular momentum J in contrast to partial wave analyses i...
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Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with long-lived four-particle spin-zero bound states called tetrons. We show that the neutral tetrons are metastable,...
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Photons may evade a synchrotron radiation constraint on quantum gravity by violating the equivalence principle. Comment: 4 pages. Comment on Jacobson et al astro-ph/0212190. Presentation revised for brief communication to Nature with extended bibliography
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Biosensors based on the principle of surface plasmon resonance (SPR) detection were used to measure biomolecular interactions in sarcomeres and changes in 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 man...
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In this talk we discuss the impact of recent experimental information, like the revised bound from E821 Brookhaven experiment on gmu - 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...
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The recent WMAP data provide a rather restricted range of the Cold Dark Matter (CDM) density $ \Omega_{CDM} h^2 $ of unprecedented accuracy. We combine these new data along with data from BNL E821 experiment measuring $ {(g_{\mu}-2)}$, $ $the {$b\goes s \gamma$} branching ratio and the light Higgs boson mass bound from LEP, to update our analysis o...
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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 \ga...
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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...
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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...
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Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of αs, sin2θW, the lower limit on the lifetime for decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, accommodating the experimental values of αs and sin2θW and other constraints, while yielding a p→e/μ+π0 lifetime beyond the...
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It has recently been pointed out that generic models of quantum gravity must contend with severe phenomenological constraints imposed by gravitational Čerenkov radiation, neutrino oscillations and the cosmic microwave background radiation. We show how the noncritical Liouville-string model of quantum gravity we have proposed escapes these constrain...
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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 $g_{\mu}-2$ along with the light Higgs boson mass bound from LEP, in delineating regions of the parameters which are consistent with cosmological data. The effect o...
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Working in the context of the CMSSM, we argue that phenomenological constraints now require the universal soft supersymmetry-breaking scalar mass m0 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 t...
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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 gμ−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...
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Modeling space-time foam using a noncritical Liouville-string model for the quantum fluctuations of D-branes with recoil, we discuss the issues of momentum and energy conservation in particle propagation and interactions. We argue that momentum should be conserved exactly during propagation and on the average during interactions, but that energy is...
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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 non-renormalizable superpotenti...
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In this letter we explore the possibility of creating the baryon asymmetry of the universe during inflation and reheating due to the decay of a field associated with the inflaton. CP violation is attained by assuming that this field is complex with a phase that varies as the inflaton evolves. We consider chaotic and natural inflation scenarios. In...
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If the Higgs boson indeed weighs about 114 to 115 GeV, there must be new physics beyond the Standard Model at some scale ≲106 GeV. The most plausible new physics is supersymmetry, which predicts a Higgs boson weighing ≲130 GeV. In the CMSSM with R and CP conservation, the existence, production and detection of a 114 or 115 GeV Higgs boson is possib...
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We combine the constraint suggested by the recent BNL E821 measurement of the anomalous magnetic moment of the muon on the parameter space of the constrained MSSM (CMSSM) with those provided previously by LEP, the measured rate of b to s gamma decay and the cosmological relic density Omega-hsquared. Our treatment of Omega-hsquared includes carefull...