Three-dimensional noncommutative bosonization

We consider the extension of the (2+1)-dimensional$(2+1)\text{-dimensional}$ bosonization process in noncommutative (NC) spacetime. We show that the large mass limit of the effective action obtained by integrating out the fermionic fields in NC spacetime leads to the NC Chern–Simons action. The present result is valid to all orders in the noncommutative parameter θ. We also discuss how the NC Yang–Mills action is induced in the next to leading order.     

Linear dependence of deformed two-photon quadrature operators on spatial noncommutative parameter

By deriving useful formulas on the variances of the deformed two-photon quadrature operators in noncommutative space, we show that the variances in general have a linear dependence on the spatial noncommutative parameter θ  , significantly different from the previous θ²${\theta }^2$-dependence results. The θ  -dependence instead of θ²${\theta }^2$-dependence results make the scheme of testing the space noncommutativity via measuring such variances much easier to realize experimentally, well within the reach of nowadays technology.     

Double transverse-spin asymmetries in Drell–Yan processes with antiprotons

We present next-to-leading order predictions for double transverse-spin asymmetries in Drell–Yan dilepton production initiated by proton–antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: 30?s?200 GeV²$30?s?200{\text{GeV}}^2$ and 2?M?7 GeV$2?M?7\text{GeV}$ is examined. The Drell–Yan asymmetries turn out to be large, in the range 20–40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions.     

First observation of electronic structure of the even parity boron acceptor states in diamond

We use electronic Raman scattering for studying the band structure of the ns$\mathrm{n}s$ boron acceptor states in diamond. For the first time, the spin–orbit splitting of these acceptor states and the 1s→ns$1s\to \mathrm{n}s$ Lyman series of transitions are observed. The spin–orbit splitting linearly increases with n number. Lyman series exhibit fine structure consisting of four bands each. The energy spacing between series is equal to ∼13 meV$\sim 13\text{meV}$. Evolution of Raman spectra of the boron-doped diamond with increasing boron concentration is shown. Mott transition is revealed in Raman spectrum. Correct values of Luttinger parameters for diamond are specified.     

Comment on noncommutative deformation of instantons

It was argued in [Y. Maeda, A. Sako, Noncommutative deformation of instantons, J. Geom. Phys. 58 (2008) 1784] that the noncommutative deformation of instantons on a 4-torus T⁴$T^4$ should alter the instanton numbers for arbitrary noncommutativity parameter θ$\theta$. We show that this is not the case for the U(N²)$U\left(N^2\right)$ theory discussed there. And we discuss the instanton numbers in general gauge theories on the noncommutative T⁴$T^4$.     

High energy improved scalar quantum field theory from noncommutative geometry without UV/IR-mixing

We consider an interacting scalar quantum field theory on noncommutative Euclidean space. We implement a family of noncommutative deformations, which – in contrast to the well known Moyal–Weyl deformation – lead to a theory with modified kinetic term, while all local potentials are unaffected by the deformation. We show that our models, in particular, include propagators with anisotropic scaling z=2$z=2$ in the ultraviolet (UV). For a Φ⁴${\Phi }^4$-theory on our noncommutative space we obtain an improved UV behaviour at the one-loop level and the absence of UV/IR-mixing and of the Landau pole.     

A bound on the scale of spacetime noncommutativity from the reheating phase after inflation

In an approach to noncommutative gauge theories, where the full noncommutative behavior is delimited by the presence of the UV and IR cutoffs, we consider the possibility of describing a system at a temperature T in a box of size L. Employing a specific form of UV/IR relationship inherent in such an approach of restrictive noncommutativity, we derive, for a given temperature T  , an upper bound on the parameter of spacetime noncommutativity _ΛNC∼|θ|^−1/2${\Lambda }_{\mathrm{NC}}\sim {|\theta |}^{-1/2}$. Considering such epochs in the very early universe which are expected to reflect spacetime noncommutativity to a quite degree, like the reheating stage after inflation, or believable pre-inflation radiation-dominated epochs, the best limits on _ΛNC${\Lambda }_{\mathrm{NC}}$ are obtained. We also demonstrate how the nature and size of the thermal system (for instance, the Hubble distance versus the future event horizon) can affect our bounds.     

Dirac equation in noncommutative space for hydrogen atom

We consider the energy levels of a hydrogen-like atom in the framework of θ  -modified, due to space noncommutativity, Dirac equation with Coulomb field. It is shown that on the noncommutative (NC) space the degeneracy of the levels 2S_1/2$2S_{1/2}$, 2P_1/2$2P_{1/2}$ and 2P_3/2$2P_{3/2}$ is lifted completely, such that new transition channels are allowed.     

Implications of a viscosity bound on black hole accretion

Motivated by the viscosity bound in gauge/gravity duality, we consider the ratio of shear viscosity (η) to entropy density (s  ) in black hole accretion flows. We use both an ideal gas equation of state and the QCD equation of state obtained from lattice for the fluid accreting onto a Kerr black hole. The QCD equation of state is considered since the temperature of accreting matter is expected to approach ¹⁰¹² K${10}^{12}\text{K}$ in certain hot flows. We find that in both the cases η/s$\eta /s$ is small only for primordial black holes and several orders of magnitude larger than any known fluid for stellar and supermassive black holes. We show that a lower bound on the mass of primordial black holes leads to a lower bound on η/s$\eta /s$ and vice versa. Finally we speculate that the Shakura–Sunyaev viscosity parameter should decrease with increasing density and/or temperatures.     

Strange stars properties calculated in the framework of the Field Correlator Method

We calculate the strange star properties in the framework of the Field Correlator Method. We find that for gluon condensate values G₂$G_2$ in the range 0.006–0.007 GeV⁴$0.006\text{–}0.007{\text{GeV}}^4$, which give a critical temperature Tc∼170 MeV$T_c\sim 170\text{MeV}$ at μc=0${\mu }_c=0$, the sequences of strange stars are compatible with some of the semi-empirical mass–radius relations and data obtained from astrophysical observations.     

Phonon-assisted optical bands of nanosized powdery SrAl2O4:Eu crystals: Evidence of a multimode Pekarian

A stoichiometric powder composed of nanosized grains of SrAl₂O₄:Eu²⁺ was synthesized by combustion method at 500 °C with the subsequent calcination at 1000 °C. The zero-phonon line position, parameter of the Stokes shift, heat release factor and effective phonon energy were studied experimentally and analyzed in the framework of the multimode Pekar–Huang–Rhys model. Experimental data show that the optical 4f–5d$4f\text{–}5d$ transitions in Eu²⁺ ion exhibit a broad asymmetric electron–vibrational bands with a pronounced structure near the maxima. The form-function of the absorption and luminescence bands are theoretically analyzed in the framework of the model of the linear electron–vibrational interaction assuming strong coupling with the local vibration (estimated Pekar–Huang–Rhys parameter a=2S=10$a=2S=10$ and frequency ?ω=509 cm⁻¹$?\omega =509{\text{cm}}^{-1}$) and relatively weak interaction with the crystal phonons. The last results in an effective temperature dependent broadening of the discrete lines corresponding to the local vibrations and to a specific shape of the whole phonon assisted band (multimode Pekarian). Providing specific interrelation between the key parameters the calculated absorption and luminescence bands exhibit peculiar temperature dependent structured peaks in a qualitative agreement with the experimental data.     

Eikonal contributions to ultra high energy neutrino–nucleon cross sections in low scale gravity models

We calculate low scale gravity effects on the cross section for neutrino–nucleon scattering at center of mass energies up to the Greisen–Zatsepin–Kuzmin (GZK) scale, in the eikonal approximation. We compare the cases of an infinitely thin brane embedded in n=5$n=5$ compactified extra-dimensions, and of a brane with a physical tension MS=1 TeV$M_S=1\text{TeV}$ and MS=10 TeV$M_S=10\text{TeV}$. The extra dimensional Planck scale MD$M_D$ is set at ¹⁰³ GeV${10}^3\text{GeV}$ and 2×¹⁰³ GeV$2\times {10}^3\text{GeV}$. We also compare our calculations with neutral current standard model calculations in the same energy range, and compare the thin brane eikonal cross section to its saddle point approximation. New physics effects enhance the cross section by orders of magnitude on average. They are quite sensitive to MS$M_S$ and MD$M_D$ choices, though much less sensitive to n.     

Running inflation in the Standard Model

An interacting scalar field with largish coupling to curvature can support a distinctive inflationary universe scenario. Previously this has been discussed for the Standard Model Higgs field, treated classically or in a leading log approximation. Here we investigate the quantum theory using renormalization group methods. In this model the running of both the effective Planck mass and the couplings is important. The cosmological predictions are consistent with existing WMAP5 data, with 0.967?ns?0.98$0.967?n_s?0.98$ (for Ne=60$N_e=60$) and negligible gravity waves. We find a relationship between the spectral index and the Higgs mass that is sharply varying for mh∼120–135 GeV$m_h\sim 120\text{–}135\text{GeV}$ (depending on the top mass); in the future, that relationship could be tested against data from PLANCK and LHC. We also comment briefly on how similar dynamics might arise in more general settings, and discuss our assumptions from the effective field theory point of view.     

Magnetic properties of barium ferrite nanoparticles: Quantitative test of the Stoner–Wohlfarth theory for uniaxial single-domain magnetic particles

We have successfully synthesized single-domain barium ferrite particles with uniaxial anisotropy. We have coated them with amorphous silica to reduce interparticle interactions so that the assembly of these particles behaves like a noninteracting randomly oriented uniaxial single-domain particle system, a prototype for the Stoner–Wohlfarth model. From the magnetic hysteresis loops of the particle system in a wide temperature range (10–700 K$10\text{–}700\text{K}$), we simultaneously determine the magnetic anisotropic field _HK$H_K$, the reduced remanence _Mr/_Ms$M_r/M_s$, and the coercive field _HC$H_C$ in the whole temperature range below the Curie temperature. These complete sets of data allow us to quantitatively test the Stoner–Wohlfarth theory and the agreement between experiment and theory is good.     

Search for solar axions with mass around 1 eV using coherent conversion of axions into photons

A search for solar axions has been performed using an axion helioscope which is equipped with a 2.3-m long 4 T superconducting magnet, a gas container to hold dispersion-matching gas, PIN-photodiode X-ray detectors, and a telescope mount mechanism to track the sun. A mass region around ma=1 eV$m_a=1\text{eV}$ was newly explored. From the absence of any evidence, analysis sets a limit on axion–photon coupling constant to be g_aγγ<5.6–13.4×¹⁰⁻¹⁰ GeV⁻¹$g_{a\gamma \gamma }<5.6\text{–}13.4\times {10}^{\mathrm{-10}}{\text{GeV}}^{\mathrm{-1}}$ for the axion mass of 0.84<ma<1.00 eV$0.84<m_a<1.00\text{eV}$ at 95% confidence level. It is the first result to search for the axion in the g_aγγ–ma$g_{a\gamma \gamma }\text{–}{m}_a$ parameter region of the preferred axion models with a magnetic helioscope.