Mass hierarchy, mass gap and corrections to Newton’s law on thick branes with Poincaré symmetry

We consider a scalar thick brane configuration arising in a 5D theory of gravity coupled to a self-interacting scalar field in a Riemannian manifold. We start from known classical solutions of the corresponding field equations and elaborate on the physics of the transverse traceless modes of linear fluctuations of the classical background, which obey a Schrödinger-like equation. We further consider two special cases in which this equation can be solved analytically for any massive mode with $m^2\ge 0$ , in contrast with numerical approaches, allowing us to study in closed form the massive spectrum of Kaluza–Klein (KK) excitations and to analytically compute the corrections to Newton’s law in the thin brane limit. In the first case we consider a novel solution with a mass gap in the spectrum of KK fluctuations with two bound states—the massless 4D graviton free of tachyonic instabilities and a massive KK excitation—as well as a tower of continuous massive KK modes which obey a Legendre equation. The mass gap is defined by the inverse of the brane thickness, allowing us to get rid of the potentially dangerous multiplicity of arbitrarily light KK modes. It is shown that due to this lucky circumstance, the solution of the mass hierarchy problem is much simpler and transparent than in the thin Randall–Sundrum (RS) two-brane configuration. In the second case we present a smooth version of the RS model with a single massless bound state, which accounts for the 4D graviton, and a sector of continuous fluctuation modes with no mass gap, which obey a confluent Heun equation in the Ince limit. (The latter seems to have physical applications for the first time within braneworld models). For this solution the mass hierarchy problem is solved with positive branes as in the Lykken–Randall (LR) model and the model is completely free of naked singularities. We also show that the scalar–tensor system is stable under scalar perturbations with no scalar modes localized on the braneworld configuration.     

Analysis of large angle p-d elastic scattering: 100–400 MeV

An analysis is presented of large angle proton-deuteron elastic scattering experiments at deuteron energies of 291, 362 and 433 MeV and proton energies of 140 and 316 MeVon the basis of the Kerman-Kisslinger (KK) model (first order). Further analysis is made using the KK model with second order corrections included. The object of the analysis is to determine quantitatively the sensitivity of large angle scattering to the D-state probability (P_D) in the deuteron. It is found that the KK model (first order and also second order corrections included) is not very successful in fitting the data at those energies when used with existing wavefunctions obtained from phenomenological potentials. A value of 6.7% for P_D gives the best fit when the model is used with the modified Moravcsik analytic fit to the Gartenhaus S-state wavefunction (the third approximation). The incoherent contributions of first and second order non-exchange processes are roughly estimated and found to be negligible. An investigation of the ambiguities in the S-state part of the deuteron wavefunction is also presented.     

Calculation of the dielectric function of Li metal

The inverse microscopic dielectric function of Li metal is evaluated within the time dependent local density approximation (TLDA) using one-electron energies and wave-functions obtained by SCF band structure calculations. Even at larger values of transferred momentum the influence of exchange and correlation is found to be quite small. Local fields are approximated by considering all elements of the dielectric matrix corresponding to the first and second shell of the reciprocal lattice vectors. Their influence is found to be orientation-dependent but in most cases quite small. However, in some cases they even cause a change of the shape of the inverse dielectric function. Our theoretical results agree quite well with measurements of the dynamic structure function by use of inelastic X-ray scattering with transferred energy up to 18 eV. Unrealistic oscillations at still higher energies as well as the narrow width of the peaks indicate the limits of a one-particle scheme.     

Evolution of the giant dipole resonance in excited 120Sn and 208Pb nuclei populated by inelastic alpha scattering

The evolution of the giant dipole resonance (GDR) in ¹²⁰Sn and ²⁰⁸Pb nuclei at excitation energies in the range of 30–130 MeV and 40–110 MeV, respectively, were studied by measuring high energy γ rays from the decay of the resonance. The excited states were populated by inelastic scattering of α particles at beam energies of 40 and 50 MeV/nucleon for ¹²⁰Sn and 40 MeV/nucleon for ²⁰⁸Pb. A systematic increase of the resonance width with increasing excitation energy was observed for both nuclei. The observed width evolution was compared to calculations employing a model that adiabatically couples the collective excitation to the nuclear shape, and to a model based on the collisional damping of nucleons. The adiabatic coupling model described the width evolution in both nuclei well, whereas the collisional damping calculation could describe the width evolution only in ²⁰⁸Pb. Light-particle inelastic scattering populates low angular momentum states in the target nucleus. The observed width increase is therefore interpreted to be predominantly due to fluctuations in the nuclear shape induced by temperature. This interpretation is consistent with the adiabatic model calculations and with recent angular momentum-gated measurements of the GDR in excited Sn isotopes.     

Borromean three-body heteroatomic resonances

We present an approach to analyze recent experimental evidences of Efimov resonant states in mixtures of ultracold gases, by considering two-species three-body atomic systems bound in a Borromean configuration, where all the two-body interactions are unbound. For such Borromean three-body systems, it is shown that a continuum three-body s-wave resonance emerges from an Efimov state as a scattering length or a three-body scale is moved. The energy and width of the resonant state are determined from a scaling function with arguments given by dimension-less energy ratios relating the two-body virtual state subsystem energies with the shallowest three-body bound state. The peculiar behavior of such resonances is that their peaks are expected to move to lower values of the scattering length, with increasing width, as one raises the temperature. For Borromean systems, two resonant peaks are expected in ultralow-temperature regimes, which will disappear at higher energies. It is shown how a Borromean-Efimov excited bound state turns out to a resonant state by tuning the virtual two-body subsystem energies or scattering lengths, with all energies written in units of the next deeper shallowest Efimov state energy. The resonance position and width for the decay into the continuum are obtained as universal scaling functions (limit cycle) of the dimensionless ratios of the two and three-body scales, which are calculated numerically within a zero-range renormalized three-body model.     

Resonances of Spin-1/2 Fermions in Eddington-Inspired Born-Infeld Gravity

We investigate the fermionic resonances for both chiralities in five-dimensional Eddington-inspired BornInfeld(EiBI)theory.In order to localize fermion on the brane,it needs to be considered the Yukawa coupling between the fermion and the background scalar field.In our models,since the background scalar field has kink,double kink,or anti-kink solution,the system has rich resonant Kaluza-Klein(KK)modes structure.The massive KK fermionic modes feel a volcano potential,which result in a fermionic zero mode and a set of continuous massive KK modes.The inner structure of the branes and a free parameter in background scalar field influence the resonant behaviors of the massive KK fermions.     

Universal torsion-induced interaction from large extra dimensions

We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to Z-pole observables, we find the 3sigma bound on the scale of quantum gravity to be 28 TeV for n = 2. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to sqrt[n] M(S)>/=210 TeV.     

Cosmological Kaluza–Klein branes in black brane spacetimes

We discuss the cosmological evolution of a brane in the D(>6)$D(>6)$-dimensional black brane spacetime in the context of the Kaluza–Klein (KK) braneworld scheme, i.e., to consider KK compactification on the brane. The bulk spacetime is composed of two copies of a patch of D  -dimensional black three-brane solution. The near-horizon geometry is given by AdS₅×S(D−5)${\mathit{AdS}}_5\times S^{(D-5)}$ while in the asymptotic infinity the spacetime approaches D-dimensional Minkowski. We consider the brane motion from the near-horizon region toward the spatial infinity, which induces cosmology on the brane. As is expected, in the early times, namely when the brane is located in the near-horizon region, the effective cosmology on the brane coincides with that in the second Randall–Sundrum (RS II) model. Then, the brane cosmology starts to deviate from the RS type one since the dynamics of KK compactified dimensions becomes significant. We find that the brane Universe cannot reach the asymptotic infinity, irrespectively of the components of matter on the brane.     

Eikonal expansion in electron scattering: I. Elastic scattering

A systematic eikonal expansion for the scattering of high-energy electrons from nuclei is derived which starts from the iterated Dirac equation. The resulting scattering amplitude is written in an impact parameter representation depending on eikonal phases which are proportional to inverse powers of the energy. The first two correction terms to the leading Glauber-Baker amplitude are calculated. For a Coulomb potential they agree with a sinθ-expansion of the relativistic Coulomb scattering amplitude. In the case of scattering from an extended charge distribution at sufficiently high energies numerical partial wave calculations are accurately reproduced.     

Direct numerical reconstruction of inelastic cross sections from REELS and ISS spectra

The reconstruction of inelastic scattering cross sections faces two problems: the measured signal (energy spectrum) is a multiple scattering signal; the inelastic energy loss is nonuniform over the target depth. In this paper, we present a method for numerical reconstruction of cross sections from characteristic energy loss spectra, which efficiently solves both problems within a multilayer model. It is shown that the inverse problem of cross section extraction in the three-layer model is ill-conditioned, and the method is practically inapplicable to the three-layer model. The direct numerical reconstruction method yields a strongly “noised” result and can be applied only to obtain a priori information on the inelastic cross section form for further fitting. Using a combination of two methods, inelastic scattering cross sections were reconstructed for aluminum from characteristic energy loss spectra at probe beam energies of 5 and 40 keV. It is shown that ionization in solids should be described as a local process and as a collective one using the dispersion formula similarly to the case of excitation plasmons.     

Gravitational scattering in the ADD model revisited

It is argued that the assumption that the standard model particles live on a finite brane in the ADD model does in itself imply a finite propagator for virtual Kaluza–Klein mode exchange. The part of the propagator relevant for large distance scattering is cut-off-independent for scattering at distances large compared to the brane width. The matrix element corresponding to this part can also, at least for an odd number of extra dimensions, be Fourier transformed to position space, giving back the extra-dimensional version of Newton’s law. For an even number of extra dimensions a corresponding result is found by requiring that Newton’s law should be recovered. PACS 04.50.+h; 11.10.Kk; 11.25.Mj     

矢量介子φ的动力学模型及耦合常数fφKK2,fωKK2与fρKK2的值

假设矢量介子φ(Ι=0,ι=1,m_φ=7.30m_π)是K散射交换ρ,ω以及φ介子本身而形成的共振。应用双色散关系中的N/D方法,并设ρ,ω以及交换的φ介子的质量为已知,近似求出KK的分波散射振幅。当要求该振幅能重新给出正确的共振位置(φ的质量)和宽度时,即可得出偶合常数f_φKK²、f_ωKK²与f_ρKK²所必需满足的关系,从而给出它们可能取的数值。     

Induced cosmology on a regularized brane in six-dimensional flux compactification

We consider a six-dimensional Einstein–Maxwell system compactified in an axisymmetric two-dimensional space with one capped regularized conical brane of codimension one. We study the cosmological evolution which is induced on the regularized brane as it moves in between known static   bulk and cap solutions. Looking at the resulting Friedmann equation, we see that the brane cosmology at high energies is dominated by a five-dimensional ρ²${\rho }^2$ energy density term. At low energies, we obtain a Friedmann equation with a term linear to the energy density with, however, negative coefficient in the small four-brane radius limit (i.e., with negative effective Newton's constant). We discuss ways out of this problem.     

Brane effects on extra-dimensional scenarios: a tale of two gravitons

We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four-dimensional brane located in a (nearly) flat extra-dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions, R, and a physical ultraviolet cutoff of the order of the fundamental Planck scale in the higher-dimensional theory, M. We show that, having implemented cutoffs, the radius of the extra dimensions cannot be arbitrarily large for M≳1 TeV. Moreover, for finite radii, the gravitational effects localized on the brane can substantially alter the phenomenology of collider and/or table-top gravitational experiments. This phenomenology is dictated by the presence of a massless graviton, with standard couplings to the matter fields, and a massive graviton which couples to matter in a much stronger way. While graviton KK modes lighter than the massive graviton couple to matter in a standard way, the couplings to matter of the heavier KK modes are strongly suppressed.     

Optical constants of Cu measured with reflection electron energy loss spectroscopy (REELS)

Two energy loss spectra of 1000 and 3000 eV electrons reflected from a Cu surface are analysed to give the normalized distribution of energy losses in a single surface and volume inelastic scattering process. These single scattering loss distributions are subsequently fitted to theoretical expressions for the differential inverse inelastic mean free path (DIIMFP) and differential surface excitation probability (DSEP) providing the real and imaginary part of the dielectric function in terms of a set of Drude-Lorentz oscillators. The optical constants obtained in this way are subjected to several sum rule checks and compared with other experimental data and with density-functional-theory (DFT) calculations. The present optical data agree excellently with the DFT-results, while the earlier optical data deviate significantly from these two data sets for energies below 30 eV. The mean free path for inelastic electron scattering for energies below 2000 eV is derived from the dielectric data and is found to agree satisfactorily with values reported earlier.     

Stimulated Brillouin scattering of Q-switched laser pulses in large-core optical fibres

Q-switched Nd : glass laser pulses of 60 ns duration are transmitted through multimode fused-silica fibres of 0.4–1 mm core diam and lengths of up to 20 m. For laser radiation with narrow spectral width, stimulated Brillouin scattering (SBS) is observed for energies well below the threshold energy of fibre damage. The SBS threshold is shifted beyond the threshold of fibre damage through increasing the spectral width of the laser radiation. The SBS threshold energies of step-index and gradient-index fibres are measured for various fibre and laser parameters.     

Dynamical casimir effect in braneworlds

In braneworld cosmology the expanding Universe is realized as a brane moving through a warped higher-dimensional spacetime. Like a moving mirror causes the creation of photons out of vacuum fluctuations, a moving brane leads to graviton production. We show that, very generically, Kaluza-Klein (KK) particles scale like stiff matter with the expansion of the Universe and can therefore not represent the dark matter in a warped braneworld. We present results for the production of massless and KK gravitons for bouncing branes in five-dimensional anti-de Sitter space. We find that for a realistic bounce the back reaction from the generated gravitons will be most likely relevant. This Letter summarizes the main results and conclusions from numerical simulations which are presented in detail in a long paper [M. Ruser and R. Durrer, arXiv:0704.0790].     

N-soliton quantum scattering in the sine-Gordon theory

The quantum treatment of soliton scattering in the sine-Gordon model, using the path integral collective coordinate method is generalized to N solitons. The solitions. The first quantum correction to the phase shift of N-soliton scattering is equal to the zero-point energy of an effective multi-soliton Hamiltonian. The energies of the oscillators of this Hamiltonian are shown to be equal to the stability angles of a complete set of solutions of the Schrödinger equation for small fluctuations around a classical N-soliton. Consequently, calculating the fluctuations and their stability angles by the inverse scattering method, we obtain the energies of the oscillators. The first quantum correction to the phase shift (the O(1) part in a development in powers of γ) is evaluated by summing the stability angles. This result is in agreement with the “exact” scattering amplitude conjectured by Faddeev, Kulish and Korepin.     

Surface plasmon excitation at a Au surface by 150-40,000 eV electrons

Spectra of electrons with energies between 5 and 40 keV reflected from a homogeneous Au surface have been measured and analyzed to give the normalized distribution of energy losses in a single surface and volume excitation, as well as the total probability for excitation of surface plasmons. The resulting single scattering loss distributions compare excellently in (absolute units) with data from previous work taken at lower energies (150-3400 eV). An empirical relationship is derived for the total surface excitation probability as a function of the energy. For high energies the surface scattering zone represents only a small fraction of a typical electron trajectory and hence interference effects should be small at these energies. Since we find that both the energy dependence of the surface plasmon excitation probability and the shape of the single scattering loss distributions are the same at high and low electron energies, we conclude that there is no evidence for interference effects in the entire energy range studied.     

飞秒激光与薄膜Cu靶作用时质子能谱实验

采用飞秒激光辐照固体薄膜Cu靶的方式对质子束的产生及质子束能谱开展了实验研究。在SILEX-Ⅰ飞秒激光装置上,保持脉宽为30 fs不变,测量了不同激光能量和功率密度下辐照7 m Cu靶时的质子能谱。研究结果表明:质子沿着靶背法线方向发射,质子在一定能量处出现截断;随着质子束能量的增加,质子束流减小;轰击厚为7 m的Cu靶时,激光能量越大则质子束流越强;随着激光功率密度的增加,质子截止能也随之增加。