Mimicking trans-Planckian effects in the CMB with conventional physics

We investigate the possibility that fields coupled to the inflaton can influence the primordial spectrum of density perturbations through their coherent motion. For example, the second field in hybrid inflation might be oscillating at the beginning of inflation rather than at the minimum of its potential. Although this effect is washed out if inflation lasts long enough, we note that there can be up to 30e-foldings of inflation prior to horizon crossing of COBE fluctuations while still giving a potentially visible distortion. Such pumping of the inflaton fluctuations by purely conventional physics can resemble trans-Planckian effects which have been widely discussed. The distortions which they make to the CMB could leave a distinctive signature which differs from generic effects like tilting of the spectrum.     

The numerical integration of relative equilibrium solutions. The nonlinear Schrodinger equation

We analyse different error propagation mechanisms for conservativeand nonconservative time-integrators of nonlinear Schrödingerequations. We use a geometric approach based on interpretingwaves as relative equilibria.     

Controlling the spatial orientation of molecular actuators: polarized photoisomerization of 2-nitro-9-(2,2,2-triphenylethylidene)fluorene in a thin polymer matrix

The molecule 2-nitro-9-(2,2,2-triphenylethylidene)fluorene (NTEF) was studied as a potential light-driven molecular motor. Absorption at 355 nm causes a reversible spatial reorientation of the angular distribution of the dibenzofulvene rotor moiety of NTEF when immobilized in a poly(methyl methacrylate) (PMMA) matrix adsorbed on a fused silica surface in air at room temperature. The photoreorientation dynamics was probed by polarized normal incidence cavity ringdown spectroscopy (NICRDS) when the matrix was irradiated by linearly polarized "drive" light. Polarized drive irradiation at 355 nm creates a "hole" in the angular distribution of the molecular transition dipoles. Changing the polarization of the drive beam refills the hole, creating a new hole. A stochastic model was fitted to the experimental hole burning measurements to obtain a photoreorientation quantum yield (Φ(reorient) = 0.014). The photoreorientation process appears to be driven by photoisomerization of the exocyclic dibenzofulvene double bond of NTEF.     

Comparative analysis of uniaxial strain shock tests and Taylor tests for maraging steels

High-strength constructional 38XH3MΦA steel and three kinds of maraging steel were tested to determine the yield stress under dynamic loading. The 38XH3MΦA steel was used as central test material to work out the experimental technique and compare the results obtained in different test methods. Results obtained in the plane shock tests under uniaxial strain condition show roughly the same yield stress values as those obtained in Taylor tests.     

Studies of cosmic gamma-ray bursts and soft gamma repeaters in the Russian-American Konus-Wind experiment

The studies of the cosmic gamma-ray bursts and soft gamma repeaters that have been performed in the Russian-American Konus-Wind experiment during the last several years have been summarized. The experiment has been continuously performed using the Konus Russian scientific instrument on the Wind American spacecraft since 1994 under the optimal interplanetary space conditions in the absence of noise caused by the Earth’s radiation belts and the shadowing of detectors. Two high-sensitivity detectors have constantly observed the entire celestial sphere and recorded detailed time and spectral characteristics of bursts in a wide range of energies (20 keV–15 MeV). The Konus-Wind data have been widely used in the present-day multiwave studies of gamma-ray bursts.     

Collective oblate rotation at high spins in neutron-rich 180Hf

We report on experimental evidence for collective oblate rotation becoming favored at high spins in a rigid, well-deformed, axially symmetric nucleus. Excited states established up to spin 20variant Planck's over 2pi in 180Hf are consistent with predictions that nucleon alignments would favor oblate over prolate shapes at high spins in neutron-rich Hf isotopes. The results highlight the influence of valence orbitals on the interplay between nucleon alignments and nuclear shapes and provide a rare example of independent particle dynamics in competing potential wells.     

Angular distributions and structure functions from two-jet events at the CERN SPS pp collider

The two-jet cross section measured in the UA1 apparatus at the CERN $\text{p}\text{p}$ Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x₁ and x₂. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x₂ and x₂, as expected in vector gluon theories (QCD). The differential cross section in x₁ and x₂ is consistent with factorization and provides a measurement of the proton structure function $\text{F(x) = G(x) +}\text{4}\text{9}\text{[Q(x) +}\text{Q}\text{(x)]}$ at values of the four-momentum transfer squared, -t? ≈ 2000 GeV². Over the range x = 0.10?0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (?9.5x).     

Quadrupole moments and the structure of the even titanium and chromium nuclei

The energies of the six circular transitions (n = 13 → n = 12 through n = 8 → n = 7) of the K^?Pb exotic atom have been measured to high precision (typically ～ 50 ppm) using Ge (Li) spectrometers. The data acquisition system was computer controlled and stabilized, the energy calibration spectrum was taken simultaneously with the data spectrum. The experimental energies of the six transitions were corrected for ADC nonlinearities and data-calibration spectrum shifts, as well as the presence of unresolved noncircular transition contaminants. The energies of five of the transitions (13 → 12 through 9 → 8) were computed from quantum electrodynamics, including all significant orders of vacuum polarization, electron screening and nuclear polarization. The mass of the K^? was adjusted to achieve a best fit with the experimental energies: the result was m_K^? = 493.657 ± 0.020 MeV.     

Coulomb excitation paths of high-K isomer bands in 178Hf

Three distinctly different mechanisms are shown to populate the K(pi)=6(+) (t(1/2)=77 ns), 16(+) (31 yr), and 8(-) (4 s) isomer bands of 178Hf by Coulomb excitation. High spin states of the three isomer bands were populated by Coulomb excitation of a hafnium target with a 650 MeV 136Xe beam. Although direct population of high-K bands is highly K-forbidden, isomer bands in 178Hf were populated up to spins 13(+)(K=6), 20(+)(K=16), and 14(-)(K=8) with in-band gamma yields of approximately 10(-4) of the ground state band. The data are consistent with a rapid increase in K mixing with increasing spin in the isomer bands.