Cosmic acceleration and crossing of in non-minimal modified Gauss–Bonnet gravity

Modified Gauss–Bonnet, i.e., f(G) gravity is a possible explanation of dark energy. Late time cosmology for the f(G) gravity non-minimally coupled with a free massless scalar field have been investigated in Ref. [S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Phys. Lett. B 651 (2007) 224, arXiv:0704.2520 [hep-th]; S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Progr. Theor. Phys. Suppl. 172 (2008) 81, arXiv:0710.5232]. In this Letter we generalize the work of Ref. [S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Phys. Lett. B 651 (2007) 224, arXiv:0704.2520 [hep-th]; S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Progr. Theor. Phys. Suppl. 172 (2008) 81, arXiv:0710.5232] by including scalar potential in the matter Lagrangian which is non-minimally coupled with modified Gauss–Bonnet gravity. Also we obtain the conditions for having a much more amazing problem than the acceleration of the universe, i.e. crossing of ω=−1, in f(G) non-minimally coupled with tachyonic Lagrangian.     

On ‘light’ fermions and proton stability in ‘big divisor’ D3/D7 large volume compactifications

Building on our earlier work (Misra and Shukla, Nucl. Phys. B 827:112, 2010; Phys. Lett. B 685:347–352, 2010), we show the possibility of generating “light” fermion mass scales of MeV–GeV range (possibly related to the 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 Σ _B . This part of the paper is an expanded version of the latter half of Sect. 3 of a published short invited review (Misra, Mod. Phys. Lett. A 26:1, 2011) written by one of the authors [AM]. Further, we also show that there are no SUSY GUT-type dimension-five operators corresponding to proton decay, and we estimate the proton lifetime from a SUSY GUT-type four-fermion dimension-six operator to be 10⁶¹ years. Based on GLSM calculations in (Misra and Shukla, Nucl. Phys. B 827:112, 2010) for obtaining the geometric K?hler potential for the “big divisor,” using further the Donaldson’s algorithm, we also briefly discuss in the first of the two appendices the metric for the Swiss-Cheese Calabi–Yau used, which we obtain and which becomes Ricci flat in the large-volume limit.     

The Microwave Spectrum of m-Tolunitrile: Methyl Internal Rotation and N Nuclear Quadrupole Coupling

The microwave spectrum of m-tolunitrile (3-methylbenzonitrile, m-C₆H₄CH₃CN) has been investigated in the frequency range from 1 to 4 and 8 to 26.5 GHz. The spectra in the two lowest states of internal methyl rotation (m = 0, ±1) were recorded by means of pulsed molecular beam Fourier transform microwave (MB-FTMW) spectrometers. The interpretation of the spectra was based on an asymmetric frame–symmetric top Hamiltonian with inclusion of centrifugal distortion terms and first-order contributions from ¹⁴N nuclear quadrupole coupling. A least-squares analysis yielded the rotational constants A = 3295.9103(10) MHz, B = 1199.1188(2) MHz, C = 883.9223(1) MHz, all elements of the nuclear quadrupole coupling tensor χ_aa = −3.626(1) MHz, χ_bb = 1.684(1) MHz, χ_cc = 1.943(1) MHz, and χ_ab = −1.870(3) MHz, as well as the threefold barrier to internal rotation, V₃ = 14.2 cm⁻¹, and the angle between the internal rotor axis and the principal moment of inertia a axis, θ = 42.66°, using fixed values for the sixfold barrier term V₆ (−11 cm⁻¹) and the moment of inertia of the methyl top I_α (3.16 u Ų).     

Dynamics of geometric discord and measurement-induced nonlocality at finite temperature

By using geometric measure of discord (GMOD) [B. Dakić, V. Vedral, Č. Brukner, Phys. Rev. Lett. 105, 109502 (2010)] and measurement-induced nonlocality (MIN) [S. Luo, S. Fu, Phys. Rev. Lett. 106, 120401 (2011)], we investigate quantum correlation of a pair of two-level systems, each of which is interacting with a reservoir at finite temperature T. We show that, for a broad class of states of the system, GMOD and MIN can endure sudden death, and there is no asymptotic decay for MIN while asymptotic decay exists for GMOD. We also give the dynamics of GMOD and MIN with respect to the temperature and illustrate their different characteristics.     

On the geometry and homology of certain simple stratified varieties

We study certain mild degenerations of algebraic varieties which appear in the analysis of a large class of supersymmetric theories, including superstring theory. We analyze Witten’s σ-model [Nucl. Phys. B 403 (1993) 159] and find that the non-transversality of the superpotential induces additional singularities and a stratification of the ground state variety. This stratified variety admits certain homology groups such that ⊕_qH^2q satisfies the “Kähler package” of requirements [Ann. Math. Studies 102 (1982) 303]. Also, this ⊕_qH^2q extends the “flopped” pair of small resolutions [Nucl. Phys. B 416 (1994) 414; Nucl. Phys. B 330 (1990) 49; Commun. Math. Phys. 119 (1988) 431] to an “(exo)flopped” triple, and is compatible with both mirror symmetry [S.-T. Yau (Ed.), Mirror Manifolds, International Press, Hong Kong, 1990; B. Greene, S.-T. Yau (Eds.), Mirror Manifolds II, International Press, Hong Kong, 1996] and string theory [Mod. Phys. Lett. A 12 (1997) 521; Nucl. Phys. B 451 (1995) 96] results. Finally, we revisit the conifold transition [Nucl. Phys. B 330 (1990) 49] as it applies in our formalism.     

Polarization spectroscopy of ion-pair states of ICl

Molecular constants for the E0⁺(³P₂) and 1(³P₂) ion-pair states of ICl vapor have been determined using sequential two-photon polarization-labeling spectroscopy. The two states are coupled by a heterogeneous perturbation which is analyzed in some detail for low-lying vibrational levels of 1(³P₂). The I³⁵Cl potential constants for the 1(³P₂) state and the rotation-vibration constants for the set of f sublevels—i.e., the constants unaffected by coupling with the E state—are (in cm⁻¹) 1(³P₂): Y_0,0= 39103.814(32), Y_1,0= 170.213(15), Y_2,0= −0.4528(22), Y_3,0= −7.0(12) × 10⁻⁴, Y_4,0= −1.48(24) × 10⁻⁵ and Y_5,0= −6.6(19) × 10⁻⁸, Y^(f)_0,1= 5.6878(17) × 10⁻² Y^(f)_1,1= −2.110(24) × 10⁻⁴, Y^(f)_2,1= −1.23(62) × 10⁻⁷, and Y^(f)_0,1= −3.08(22) × 10⁻⁸Likewise, the I³⁵Cl constants determined for the E 0⁺(³P₂) state are E 0⁺(³P₂: Y_0,0= 39054.38(61), Y_1,0= 166.96(10), Y_2,0 = −0.3995(42), Y_0,1= 5.738(31) × 10⁻², and Y_1,1= −1.67(26) × 10⁻⁴Practical constraints in pumping the sequence E 0⁺ ← B 0⁺ ← × 0⁺ restrict the analysis of the E state to levels v = 9–15. Given the long extrapolation to the equilibrium state the 3σ statistical uncertainties quoted for these constants should be treated with caution.     

Phase shift analysis and extraction of structure functions for Coulomb distortion on (e, e'p) reactions at high electron energies

New results for the double beta decay of ⁷⁶ Ge are presented. They are extracted from data obtained with the HEIDELBERG-MOSCOW experiment, which operates five enriched ⁷⁶ Ge detectors in an extreme low-level environment in the Gran Sasso underground laboratory. The two-neutrino-accompanied double beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in a half-life of T _1/2 ^2ν = [1.55±0.01(stat)^+0.19 _-0.15(syst)]×10²¹ y. The lower limit on the half-life of the 0νββ decay obtained with pulse shape analysis is T _1/2 ^0ν > 1.9×10²⁵(3.1×10²⁵) y with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana-neutrino mass of 0.35 eV (0.27 eV) using the matrix elements of A. Staudt et al.'s work (Europhys. Lett. 13, 31 (1990)). This is the most stringent limit at present from double beta decay. No evidence for a majoron-emitting decay mode is observed. Received: 22 August 2001 / Accepted: 18 October 2001     

Exceptional sensitivity to neutrino parameters with a two-baseline Beta-beam set-up

We examine the reach of a Beta-beam experiment with two detectors at carefully chosen baselines for exploring neutrino mass parameters. Locating the source at CERN, the two detectors and baselines are: (a) a 50 kton iron calorimeter (ICAL) at a baseline of around 7150 km which is roughly the magic baseline, e.g., ICAL@INO, and (b) a 50 kton Totally Active Scintillator Detector at a distance of 730 km, e.g., at Gran Sasso. We choose ⁸B and ⁸Li source ions with a boost factor γ of 650 for the magic baseline while for the closer detector we consider ¹⁸Ne and ⁶He ions with a range of Lorentz boosts. We find that the locations of the two detectors complement each other leading to an exceptional high sensitivity. With γ=650 for ⁸B/⁸Li and γ=575 for ¹⁸Ne/⁶He and total luminosity corresponding to 5×(1.1×10¹⁸) and 5×(2.9×10¹⁸) useful ion decays in neutrino and antineutrino modes respectively, we find that the two-detector set-up can probe maximal CP violation and establish the neutrino mass ordering if sin²2θ₁₃ is 1.4×10⁻⁴ and 2.7×10⁻⁴, respectively, or more. The sensitivity reach for sin²2θ₁₃ itself is 5.5×10⁻⁴. With a factor of 10 higher luminosity, the corresponding sin²2θ₁₃ reach of this set-up would be 1.8×10⁻⁵, 4.6×10⁻⁵ and 5.3×10⁻⁵ respectively for the above three performance indicators. CP violation can be discovered for 64% of the possible δ_CP values for sin²2θ₁₃10⁻³ (8×10⁻⁵), for the standard luminosity (10 times enhanced luminosity). Comparable physics performance can be achieved in a set-up where data from CERN to INO@ICAL is combined with that from CERN to the Boulby mine in United Kingdom, a baseline of 1050 km.     

Double exchange models: self consistent renormalisation

We propose a scheme for constructing classical spin Hamiltonians from Hunds coupled spin-fermion models in the limit J_H/t →∞. The strong coupling between fermions and the core spins requires self-consistent calculation of the effective exchange in the model, either in the presence of inhomogeneities or with changing temperature. In this paper we establish the formalism and discuss results mainly on the “clean” double exchange model, with self consistently renormalised couplings, and compare our results with exact simulations. Our method allows access to system sizes much beyond the reach of exact simulations, and we can study transport and optical properties of the model without artificial broadening. The method discussed here forms the foundation of our papers [Phys. Rev. Lett. 91, 246602 (2003), and Phys. Rev. Lett. 92, 126602 (2004)].     

Manifestation of ferromagnetism in lightly oxygen-doped La2CuO4 single crystals in magnetic fields H<50 Oe

The temperature and field dependences χ(T,H) in La₂CuO_4+δ single crystals with δ<0.015 have been investigated in magnetic fields 0.1<H<450 Oe by the differential magnetic susceptibility method. It was found that under oxygen doping conditions ferromagnetic regions are formed. These regions produce a characteristic curve of the magnetic susceptibility χ(T,H), which is observed only in magnetic fields of less than 50 Oe. This can be explained by the formation of ferrons [A. Aharony et al. Phys. Rev. Lett. 60, 1330 (1988); L. I. Glazman and A. S. Ioselevich, Z. Phys. B 80, 268 (1990)] in an antiferromagnetic matrix. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 152–155 (10 August 1996)     

Modelling the quark propagator

We are interested in developing covariant, confining, and asymptotically free models of hadrons. With this goal in mind we have carried out a study of dynamical chiral symmetry breaking without imposing the frequently used approximation α_s(−(p−k)²) α₅(−p_>²), where p_>² ≡ max(p², k²) for the running coupling constant in the quark Schwinger-Dyson equation. We present numerical results in Landau gauge and compare these with earlier results obtained when using this approximation. We see in this context that a gluon propagator which has the form 1/q⁴ in the infrared is too singular and must be regulated. We derive a suitably generalized expression for the pion decay constant f_π. With essentially one free parameter we are able to reproduce reasonable results for various physical quantities of interest including , and Λ_QCD.     

An energy-momentum tensor in gauge theories

We consider the renormalization of the twist two, dimension four gauge invariant operator O_μν⁽¹⁾ = − F_μσF_νσ − g_{μν 0}. By using the general theory of renormalization of gauge invariant operators, we find the gauge noninvariant operator O⁽²⁾ with which it mixes. We construct a finite combination of O⁽¹⁾ and O⁽²⁾ and show that it is an acceptable energy momentum tensor for gauge theories. We compare our energy momentum tensor with that constructed by Freedman, Muzinich, and Weinberg.     

Direct measurement of the pseudoscalar decay constant

The absolute branching fraction for the decay D⁺→μ⁺ν has been directly measured based on a data sample of about 33 pb⁻¹ collected around with the BES-II detector at the BEPC collider. A total of 5321±149±160 D⁻ mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D⁻ mesons, 2.67±1.74 purely leptonic decay events of D⁺→μ⁺ν_μ are observed. Those yield the branching fraction of , and a corresponding value of the pseudoscalar decay constant .     

Isobar-hole description of pion-nucleus inelastic scattering

The Δ−h formalism is applied to a systematic study of π-nucleus inelastic scattering. In the formal part of this work, the following basic excitation mechanisms are identified in π-nucleus inelastic scattering: coupling to the transition density, coupling to convection and magnetization currents and coupling to the spin-flux tensor. The properties of these modes of coupling are discussed, in particular implications of certain symmetries of the corresponding transition amplitudes. As an application, calculations are presented for various excitations in π−¹²C scattering in the resonance region. In the comparison with the data the interplay is emphasized between the nuclear structure aspects, on the one hand, and the reaction mechanisms contained in the Δ−h formalism, on the other hand.     

The chemiluminescent flame spectrum of SiO

The band systems of the SiO molecule have been excited in a flame produced by the chemiluminescence of SiCl₄ vapor reacting with oxygen atoms in the presence of an argon atmosphere. A general survey has been made of the emission spectrum of this flame and the various band systems lying in the region 2300–4600 Å have been identified. Many new bands have been observed and have been assigned to the SiO molecule. The emission bands tentatively attributed to a new ¹Σ⁻-¹Σ⁻ transition of neutral SiO [H. Bredohl, R. Cornet, I. Dubois, and F. Remy, Can. J. Phys. 51, 2322 (1973)] and reassigned by R. F. Barrow and T. J. Stone [J. Phys. B. 8, L13 (1975)] to belong to the known E¹Σ⁺-X¹Σ⁺ system of SiO have been extended in the present source. They are shown to confirm the Barrow and Stone assignments. A few bandheads corresponding to the isotopic species ²⁹SiO and ³⁰SiO have been observed for A¹Π-X¹Σ⁺ system. In addition, several strong unidentified bands have been reported.     

Fourier Transform Spectroscopy of theYΣ–XΠiTransition of CuO

TheY²Σ⁺–X²Π_inear-infrared electronic transition of CuO was observed at high resolution for the first time. The spectrum was recorded with the Fourier transform spectrometer associated with the McMath–Pierce Solar Telescope at Kitt Peak. The excited CuO molecules were produced in a low pressure copper hollow cathode sputter with a slow flow of oxygen. Constants for theY²Σ⁺states of CuO are:T₀= 7715.47765(54) cm⁻¹,B= 0.4735780(28) cm⁻¹,D= 0.822(12) × 10⁻⁶cm⁻¹,H= 0.46(10) × 10⁻¹⁰cm⁻¹, γ = −0.089587(42) cm⁻¹, γ_D= 0.1272(79) × 10⁻⁶cm⁻¹,b_F= 0.12347(22) cm⁻¹, andc= 0.0550(74) cm⁻¹. ImprovedX²Π_iconstants are also presented.     

Rotational absorption spectrum of methylene fluoride in the 20–100 cm region

The pure rotational spectrum of CH₂F₂ was recorded in the 20–100 cm⁻¹ spectral range and analyzed to obtain rotation and centrifugal distortion constants. Analysis of the data yielded rotation constants: A = 1.6392173 ± 0.0000015, B = 0.3537342 ± 0.00000033, C = 0.3085387 ± 0.00000027, τ_aaaa = −(7.64 ± 0.46) × 10⁻⁵, τ_bbbb = −(2.076 ± 0.016) × 10⁻⁶, τ_cccc = −(9.29 ± 0.12) × 10⁻⁷, T₁ = (4.89 ± 0.20) × 10⁻⁶, and T₂ = −(1.281 ± 0.016) × 10⁻⁶cm⁻¹.     

The hot bands of silane between 2120 and 2270 cm

The infrared spectrum of the SiH₄ molecule has been recorded between 2040 and 2320 cm⁻¹ using the high-resolution Fourier interferometer of the Laboratoire de Photophysique Moléculaire (Orsay, France). The resolution was 5.4 × 10⁻³ cm⁻¹. In this region, many lines were previously analyzed and assigned to the ν₁/ν₃ stretching dyad of ²⁸SiH₄, ²⁹SiH₄, and ³⁰SiH₄ molecules [J. Mol. Spectrosc. 143 (1990) 35]. However, several lines in the spectrum were not assigned. The results obtained in our previous study [J. Mol. Spectrosc. 197 (1999) 307] of the infrared spectrum of ²⁸SiH₄, in the bending-stretching tetrad region at 3100 cm⁻¹, enabled us to assign 204 of the observed transitions to hot bands (the ν₁ + ν₂/ν₁ + ν₄/ν₂ + ν₃/ν₃ + ν₄ bending-stretching tetrad minus the ν₂/ν₄ bending dyad). These transitions were used to refine the set of the Hamiltonian parameters of the bending-stretching tetrad. The analysis is performed using the tensorial formalism developed in Dijon for tetrahedral molecules and implemented in the STDS software (http://www.u-bourgogne.fr/LPUB/shTDS.html).     

Analysis of the 2ν3 band of CD3F at 5.06 μm recorded under high resolution

The 2ν₃(A₁) band of ¹²CD₃F near 5.06 μm has been recorded with a resolution of 20–24 × 10⁻³ cm⁻¹. The value of the parameter (α^B − α^A) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν₀ = 1977.178(3) cm⁻¹, B″ = 0.68216(9) cm⁻¹, D″_J = 1.10(30) × 10⁻⁶ cm⁻¹, α^B = (B″ − B′) = 3.086(7) × 10⁻³ cm⁻¹, and β^J = (D″_J − D′_J) = −3.24(11) × 10⁻⁷ cm⁻¹. A value of α^A = (A″ − A′) = 2.90(5) × 10⁻³ cm⁻¹ has been obtained through band contour simulations of the R(J) and P(J) multiplets.     

Measurement of Magnitude and Sign of Heteronuclear Coupling Constants in Transition Metal Complexes

Sets of specifically tailored E.COSY-type correlation experiments and double-quantum/zero-quantum (DQ/ZQ) experiments are presented which enable the determination of sign and size of small heteronuclear coupling constants across the metal center of transition metal complexes. For the octahedrally coordinated complexes, [Ru(TPM)(H)(CO)(PPh₃)]⁺[BF₄]⁻(1) and [Ir(TPM)(H)(CO)(CO₂CH₃)]⁺[BF₄]⁻(2), 14 of 15 and 15 of 15 possible two-bond scalar coupling constants across the metal center were measured, respectively, using¹⁵N and¹⁵N/¹³C enriched samples (TPM = tris(1-pyrazolyl)methane)). The reduced coupling constants²K_X-M-Y= 4π²²J/(hγ_Xγ_Y) were found to be positive when the coupled nuclei X and Y weretranswith respect to the metal center, and negative when the coupled nuclei were incisposition. The validity of this sign rule was verified forJ_CC,J_NN,J_PN,J_PC,J_CN,J_HP,J_HC, andJ_HNcouplings. Idiosyncracies associated with 2D NMR spectra for the sign determination of coupling constants with¹⁵N which lead to corrections for the signs ofJ_HN,J_PN, andJ_CNcouplings reported previously are discussed.