The discrete specmm of the hydrogen atom moving acmss a stmng magnetic field (E = 7 x 10"-7 x IO'* G) is studied by expanding wavefunctions over a complete onhogonal basis, whose single term pmvides a correct description of an mmic state at large pseudomomenta K of the h'ansverse motion. Wavefunctions, energies, atomic sires and oscillator strengths of radiative transitions a~ calculated and analysed in a wide range of K values. AU these quantities undergo radical changes when the atom moves acioss the field. The discrete s p e c " remains infinite at arbitrary K. although the mean transverse velocity cannot exceed some maximum value for lhe bound states. Oscillator e n g t h s change by orders of magnitude and some dipole selection rules are violated.

We set new constraints on a seven-dimensional space of cosmological parameters within the class of inflationary adiabatic models. We use the angular power spectrum of the cosmic microwave background measured over a wide range of in the first flight of the MAXIMA balloon-borne experiment (MAXIMA-1) and the low results from COBE/DMR. We find constraints on the total energy density of the universe, Ω = 1.0 +0.15 −0.30 , the physical density of baryons, Ω b h 2 = 0.03 ± 0.01, the physical density of cold dark matter, Ω cdm h 2 = 0.2 +0.2 −0.1 , and the spectral index of primordial scalar fluctuations, n s = 1.08 ± 0.1, all at the 95% confidence level. By combining our results with measurements of high-redshift supernovae we constrain the value of the cosmological constant and the fractional amount of pressureless matter in the universe to 0.45 < Ω Λ < 0.75 and 0.25 < Ω m < 0.50, at the 95% confidence level. Our results are consistent with a flat universe and the shape parameter deduced from large scale structure, and in marginal agreement with the baryon density from big bang nucleosynthesis. Subject headings: cosmic microwave background-cosmology: observations-large-scale structure of universe

We construct an ionic lattice background in the framework of Einstein-Maxwell-dilaton theory in four dimensional space time. The optical conductivity of the dual field theory on the boundary is investigated. Due to the lattice effects, we find the imaginary part of the conductivity is manifestly suppressed in the zero frequency limit, while the DC conductivity approaches a finite value such that the previous delta function reflecting the translation symmetry is absent. Such a behavior can be exactly fit by the Drude law at low frequency. Moreover, we find that the modulus of the optical conductivity exhibits a power-law behavior at intermediate frequency regime. Our results provides further support for the universality of such power-law behavior recently disclosed in Einstein-Maxwell theory

We construct a gravity dual for charge density waves (CDW) in which the translational symmetry along one spatial direction is spontaneously broken. Our linear perturbation calculation on the gravity side produces the frequency dependence of the optical conductivity, which exhibits the two familiar features of CDW, namely the pinned collective mode and gapped single-particle excitation. These two features indicate that our gravity dual also provides a new mechanism to implement the metal to insulator phase transition by CDW, which is further confirmed by the fact that d.c. conductivity decreases with the decreased temperature below the critical temperature.

We construct the simplest gravitational dual model of a superconductor on Qlattices. We analyze the condition for the existence of a critical temperature at which the charged scalar field will condense. In contrast to the holographic superconductor on ionic lattices, the presence of Q-lattices will suppress the condensate of the scalar field and lower the critical temperature. In particular, when the Q-lattice background is dual to a deep insulating phase, the condensation would never occur for some small charges. Furthermore, we numerically compute the optical conductivity in the superconducting regime. It turns out that the presence of Q-lattice does not remove the pole in the imaginary part of the conductivity, ensuring the appearance of a delta function in the real part. We also evaluate the gap which in general depends on the charge of the scalar field as well as the Q-lattice parameters. Nevertheless, when the charge of the scalar field is relatively large and approaches the probe limit, the gap becomes universal with ω g 9T c which is consistent with the result for conventional holographic superconductors.

We describe the results of high-resolution numerical simulations of string-induced structure formation in open universes and those with a nonzero cosmological constant. For models with G Vh 0.1 0.2 and a cold dark matter background, we show that the linear density fluctuation power spectrum has both an amplitude at 8h 21 Mpc, s 8 , and an overall shape which are consistent within uncertainties with those currently inferred from galaxy surveys. The cosmic string scenario with hot dark matter requires a strongly scale-dependent bias in order to agree with observations. [S0031-9007(98)07015-X] PACS numbers: 98.80. Cq, 98.62.Ai, 98.65.Dx In this Letter we describe new results from an investigation of cosmic string-seeded structure formation in hot and cold dark matter models. The cosmic string scenario [1] predated inflation as a realistic structure formation model, but it proved computationally much more challenging to make robust predictions with which to confront observation. The present paper relies on high-resolution numerical simulations of a cosmic string network [2] with a dynamic range extending from before the matter-radiation transition through to deep in the matter era (developing on previous work [3]). We calculate the linear power spectrum of density perturbations P ͑k͒ induced by the strings in flat models with and without a cosmological constant, and we then extrapolate to open cosmologies. This work represents a considerable quantitative advance by incorporating important aspects of the relevant physics not included in previous treatments.In the first instance, we consider density perturbations about a flat Friedmann-Robertson-Walker (FRW) model with a cosmological constant L and which are causally sourced by an evolving string network with energymomentum tensor Q ab ͑x, h͒. In the synchronous gauge, the linear evolution equations of the radiation and cold dark matter (CDM) perturbations, d r and d c respectively, are given by (modified from [4])where Q 1 Q 00 1 Q ii , a is the scale factor, the subscript "eq" denotes the epoch of radiation-matter density equality, "0" denotes the epoch today, a dot represents a derivative with respect to conformal time h, V c 8pGr c0 ͞3H 2 0 and V L L͞3H 2 0 . It proves useful to split these linear perturbations into initial ͑I͒ and sub-

We investigate the holographic fermions over a gravitational lattice background with a rather low temperature. Since the rotation symmetry is broken on the plane, the lattice effects change the shape of the Fermi surface within the first Brillouin zone from a circle to an ellipse. When the Fermi surface intersects with the Brillouin zone boundary, the band structure with a band gap is observed through a numerical analysis. We construct a lattice model sourced by a scalar field as well as an ionic lattice model without the scalar field. In both cases we find the similar physical results.

In this letter we construct the Stückelberg holographic superconductor with Weyl corrections.Under such corrections, the Weyl coupling parameter γ plays an important role in the order of phase transitions and the critical exponents of second order phase transitions. So do the model parameters c α , α and c 4 . Moreover, we show that the Weyl coupling parameter γ and the model parameters c α , α, c 4 which together control the size and strength of the conductivity coherence peak and the ratio of gap frequency over critical temperature ω g /T