Plasma suppression of large scale structure formation in the universe

We point out that during the reionization epoch of the cosmic history, the plasma collective effect among the ordinary matter would suppress the large scale structure formation. The imperfect Debye shielding at finite temperature would induce an electrostatic pressure which, working together with the thermal pressure, would counter the gravitational collapse. As a result, the effective Jeans length, lambda[over ]_{J} is increased by a factor lambda[over ]_{J}/lambda_{J}=sqrt[8/5], relative to the conventional one. For scales smaller than the effective Jeans scale the plasma would oscillate at the ion-acoustic frequency. The modes that would be influenced by this effect lie roughly in the range 0.5h Mpc;{-1}相似文献   

Measurement of b-quark fragmentation fractions in p&pmacr; collisions at sqrt

We have studied the production of B hadrons in 1.8-TeV pp[over ˉ] collisions. We present measurements of the fragmentation fractions, f_{u}, f_{d}, f_{s}, and f_{baryon}, of produced b quarks that yield B^{+}, B^{0}, B_{s}^{0}, and Λ[over ˉ]_{b}^{0} hadrons. Reconstruction of five electron-charm final states yields f_{s}/( f_{u}+f_{d})=0.213±0.068 and f_{baryon}/( f_{u}+f_{d})=0.118±0.042, assuming f_{u}=f_{d}. If all B hadrons produced in pp[over ˉ] collisions cascade to one of these four hadrons, we determine f_{u}=f_{d}=0.375±0.023, f_{s}=0.160±0.044, and f_{baryon}=0.090±0.029. If we do not assume f_{u}=f_{d}, we find f_{d}/f_{u}=0.84±0.16.     

Multiple gap symmetries for the order parameter of cuprate superconductors from penetration depth measurements

The temperature dependence of the London penetration depth lambda was measured for an untwinned single crystal of YBa_{2}Cu_{3}O_{7-delta} along the three principal crystallographic directions (a, b, and c). Both in-plane components (lambda_{a};{-2} and lambda_{b};{-2}) show an inflection point in their temperature dependence which is absent in the component along the c direction (lambda_{c};{-2}). The data provide convincing evidence that the in-plane superconducting order parameter is a mixture of (s+d)-wave symmetry whereas it is mainly s wave along the c direction. In conjunction with previous results it is concluded that coupled s+d-order parameters are universal and intrinsic to cuprate superconductors.     

An SU(3) symmetry for light neutrinos

It is proposed that light neutrinos form a triplet in a global SU(3) symmetry in the mass eigenstate basis. Assuming that the SU(3) symmetry is broken in the direction , and after going to the flavor basis, we predict the atmospheric mixing angles sin²θ₂₃=0.5 and sinθ₁₃=0, if ν_μ–ν_τ symmetry is assumed. In the flavor basis, the diagonal part of the matrix coefficient of b (the dominant part) is found to transform like . Imposing the same condition on the matrix coefficient of a fixes the solar mixing angle, . The implications for neutrinoless double beta decay are discussed.     

Impact of symmetric gate-recess length on the DC and RF characteristics of InP HEMTs

We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(L_SD)unchanged,and obtained a group of devices with gate-recess length(L_recess)from 0.4μm to 0.8μm through process improvement.In order to suppress the influence of the kink effect,we have done SiN_X passivation treatment.The maximum saturation current density(ID_max)and maximum transconductance(g_m,max)increase as L_recess decreases to 0.4μm.At this time,the device shows ID_max=749.6 mA/mm at V_GS=0.2 V,V_DS=1.5 V,and g_m,max=1111 mS/mm at V_GS=?0.35 V,V_DS=1.5 V.Meanwhile,as L_recess increases,it causes parasitic capacitance C_gd and g_d to decrease,making f_max drastically increases.When L_recess=0.8μm,the device shows f_T=188 GHz and f_max=1112 GHz.     

The upper bound on the tensor-to-scalar ratio consistent with quantum gravity

We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the quantum gravity(QG) corrections and effective field theory(EFT). To get a minimal field excursion Δ? for enough e-folding number N, the inflaton field traverses an extremely flat part of the scalar potential, which results in the Lyth bound to be violated. We get a CMB signal consistent with Planck data by numerically computing the equation of motion for inflaton ? and using Mukhanov–Sasaki formalism for primordial spectrum. Inflation ends at Hubble slow-roll parameter ■. Interestingly, we find an excellent practical bound on the inflaton excursion in the format ■, where a is a tiny real number and b is at the order 1. To be consistent with QG/EFT and suppress the high-dimensional operators, we show that the concrete condition on inflaton excursion is ■. For n_s= 0.9649,N_e= 55, and ■0.632 MPl, we predict that the tensor-to-scalar ratio is smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT.     

Constraining spin-one color-octet resonances using CDF and ATLAS data

In this paper, we study the production of spin-one color-octet resonances (colorons) at hadron colliders in a model independent way. We use dijets data measured by CDF (at \(\sqrt{ s}=1.96\) TeV and \(\mathcal{L}=1.13\) pb^?1) and ATLAS (at \(\sqrt{ s}=7\) TeV and \(\mathcal{L}=315\) nb^?1) collaborations at the Tevatron and the LHC respectively to impose limits on the coupling of colorons to fermions. We show that CDF data still produce the more stringent limits on the coloron coupling constant.     

Effect of laser-focusing conditions on propagation and monoenergetic electron production in laser-wakefield accelerators

The effect of laser-focusing conditions on the evolution of relativistic plasma waves in laser-wakefield accelerators is studied both experimentally and with particle-in-cell simulations. For short focal-length (w_{0}lambda_{p}), a single optical filament can capture the majority of the laser energy and self-guide over distances comparable to the dephasing length, even for these short pulses (ctau approximately lambda_{p}). This allows the wakefield to evolve to the correct shape for the production of the monoenergetic electron bunches, as measured in the experiment.     

Nucleon axial charge in (2+1)-flavor dynamical-lattice QCD with domain-wall fermions

We present results for the nucleon axial charge g{A} at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16;{3} x 32 and 24;{3} x 64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_{pi} is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m{pi}=330 MeV. We also find a scaling with the single variable m{pi}L which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g{A}=1.20(6)(4) at the physical pion mass, m_{pi}=135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V>or=(2.4 fm);{3}. We argue this is a dynamical quark effect.     

Shear viscosity in a gluon gas

The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio eta/s for a gluon gas, which involves elastic gg-->gg perturbative QCD (PQCD) scatterings as well as inelastic gg<-->ggg PQCD bremsstrahlung. For alpha_{s}=0.3 we find eta/s=0.13 and for alpha_{s}=0.6, eta/s=0.076. The small eta/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.     

Magnetic excitations in an itinerant ferromagnet near quantum criticality

We determine the initial temperature dependence of the exchange splitting Delta(T) in the weak itinerant ferromagnet ZrZn2 (T{C}=28 K) using the de Haas-van Alphen effect. There is a large decrease in Delta with temperature in the range 0.5< or =T< or =4 K. A comparison of Delta(T) with the magnetization M(T) shows that the dominant process responsible for the reduction of M is not the thermal excitation of spin waves, but a repopulation of the spin- upward arrow and spin- downward arrow Fermi surfaces. This contrasts with the behavior in Fe where there is no observable change in Delta and the thermal excitation of spin waves is the only observable spin-flipping process at low temperatures.     

Quantum Electrodynamics of Atomic Resonances

A simple model of an atom interacting with the quantized electromagnetic field is studied. The atom has a finite mass m, finitely many excited states and an electric dipole moment, \({\vec{d}_0 = -\lambda_{0} \vec{d}}\), where \({\| d^{i}\| = 1, i = 1, 2, 3,}\) and \({\lambda_0}\) is proportional to the elementary electric charge. The interaction of the atom with the radiation field is described with the help of the Ritz Hamiltonian, \({-\vec{d}_0 \cdot \vec{E}}\), where \({\vec{E}}\) is the electric field, cut off at large frequencies. A mathematical study of the Lamb shift, the decay channels and the life times of the excited states of the atom is presented. It is rigorously proven that these quantities are analytic functions of the momentum \({\vec{p}}\) of the atom and of the coupling constant \({\lambda_0}\), provided \({\vert\vec{p} \vert < mc}\) and \({\vert \Im \vec{p} \vert}\) and \({\vert \lambda_{0} \vert}\) are sufficiently small. The proof relies on a somewhat novel inductive construction involving a sequence of ‘smooth Feshbach–Schur maps’ applied to a complex dilatation of the original Hamiltonian, which yields an algorithm for the calculation of resonance energies that converges super-exponentially fast.     

Physical properties of the noncentrosymmetric superconductor Mg10Ir19B16

Specific heat, electrical resistivity, and magnetic susceptibility measurements on a high quality sample of Mg10Ir19B16 provide a self-consistent determination of its superconducting properties. They indicate that Mg10Ir19B16 is a type-II superconductor [T{C}=4.45 K, kappa(0) approximately 20], with an electron-phonon coupling constant lambda{ep}=0.66. An analysis of the T-dependent specific heat shows that superconducting properties are dominated by an s-wave gap (Delta=0.7 meV). Point contact tunneling data provide evidence for multiple superconducting gaps, as expected from strong asymmetric spin-orbit coupling.     

Current noise in the vicinity of the 2D superconductor-insulator quantum critical point

Systems near to quantum critical points show universal scaling in response to external probes. We consider whether this scaling is reflected in their out-of-equilibrium fluctuations. We study current noise in the metallic state at the z=1 quantum critical point between a superconductor and an insulator in two dimensions. Using a Boltzmann-Langevin approach within a 1/N expansion, we show that the current noise obeys a universal scaling form S_{j}=TPhi[T/T_{eff}(E)], with T_{eff} proportional, variantsqrt[E]. This treatment recovers Johnson noise in thermal equilibrium and S_{j} proportional, variantsqrt[E] at strong electric fields. The latter differs significantly from both the shot noise in conventional metals (diffusive Fermi liquids) and the free carrier result, due to strong correlations between the critical bosonic excitations. Current-noise measurements could therefore help clarify the physics of the destruction of superconductivity in thin film superconductors.     

Observation of the linear stark effect in a single acceptor in Si

The Stark splitting of a single fourfold degenerate impurity located within the built-in potential of a metal-semiconductor contact is investigated using low temperature transport measurements. A model is developed and used to analyze transport as a function of temperature, bias voltage, and magnetic field. Our data is consistent with a boron impurity. We report g factors of g_{1/2}=1.14 and g_{3/2}=1.72 and a linear Stark splitting 2Delta of 0.1 meV.     

Holographic Dark Energy Model is Consistent with Pantheon SN Ia Data

We constrain three cosmological models,i.e.,ACDM model, holographic dark energy(HDE) model and R_h = ct model by using the recent Pantheon compilation of type la supernovae(SN la), the direction measurements of Hubble parameter H(z), and the baryon acoustic oscillations(BAO). The spatial curvature is considered in the ACDM model and the HDE model. We show that the HDE model in a spatially flat and HDE dominate universe has the same behavior as Rh = ct model if the characteristic parameter of the HDE model C_0 approaches to infinity. Numerical results show that the ACDM model is the best favoured one among the three models. The HDE model is consistent with observational data, the best fitting value of C_0 is around 0.8, which implies that the Rh = ct model should be modified to be compatible with the present cosmological observational data. Combing all the datasets, we give strict constraint on the Hubble constant,where h_0=0.694 ± 0.020 for the ACDM model and h_0= 0.689 ±0.019 for the HDE model.Our results imply that the tension of Hubble constant between Planck collaborations and Riess et al. has been partially relaxed. The constraint on the spatial curvature is also given,where Ω_(k0) =-0.066 ± 0.165 for the ACDM model andΩ_(k0)=0.029 ± 0.067 for the HDE model.     

Doubly heavy tetraquarks in an extended chromomagnetic model

Using an extended chromomagnetic model,we perform a systematic study of the masses of doubly heavy tetraquarks.We find that the ground states of the doubly heavy tetraquarks are dominated by the color-triplet ■configuration,which is opposite to that of fully heavy tetraquarks.The combined results suggest that the color-triplet configuration becomes more important when the mass difference between the quarks and antiquarks increases.We find three stable states that lie below the thresholds of two pseudoscalar mesons.They are the I^P=01⁺nnbb tetraquark,I^P=1⁺nncb tetraquark,and J^P=1⁺nsbb tetraquark.     

Thomae Type Formulae For Singular Z N Curves

We give an elementary and rigorous proof of the Thomae type formula for the singular curves . To derive the Thomae formula we use the traditional variational method which goes back to Riemann, Thomae and Fuchs. An important step of the proof is the use of the Szegö kernel computed explicitly in algebraic form for non-singular 1/N-periods. The proof inherits principal points of Nakayashiki’s proof (Nakayashiki in Publ. Res. Inst. Math. Sci 33(6) 987–1015, 1997) obtained for non-singular Z _N curves.