Application of the Adiabatic Selfconsistent-Collective-Coordinate Method to a Solvable Model of Prolate-Oblate Shape Coexistence

The adiabatic selfconsistent collective coordinate method is applied to an exactly solvable multi-O(4) model which simulates nuclear shape coexistence phenomena. Collective mass and dynamics of large amplitude collective motions in this model system are analysed, and it is shown that the method can well describe the tunneling motions through the barrier between the prolate and oblate local minima in the collective potential. Emergence of the doublet pattern is well reproduced.Comment: 25 pages including 9 figure

Collective Paths Connecting the Oblate and Prolate Shapes in 68Se and 72Kr Suggested by the Adiabatic Self-Consistent Collective Coordinate Method

By means of the adiabatic self-consistent collective coordinate method and the pairing-plus-quadrupole interaction, we have obtained the self-consistent collective path connecting the oblate and prolate local minima in 68Se and 72Kr for the first time. The self-consistent collective path is found to run approximately along the valley connecting the oblate and prolate local minima in the collective potential energy landscape. This result of calculation clearly indicates the importance of triaxial deformation dynamics in oblate-prolate shape coexistence phenomena.Comment: 24 pages including 5 figure

Removal of Spurious Admixture in a Self-consistent Theory of Adiabatic Large Amplitude Collective Motion

In this article we analyse, for a simple model, the properties of a practical implementation of a fully self-consistent theory of adiabatic large-amplitude collective motion using the local harmonic approach. We show how we can deal with contaminations arising from spurious modes, caused by standard simplifying approximations. This is done both at zero and finite angular momentum. We analyse in detail the nature of the collective coordinate in regions where they cross spurious modes and mixing is largest

Phase transition in exotic nuclei along the N=ZN=Z line

The abrupt structure change from the nuclei of $N=Z \le 35$ to those of $N=Z \ge 36$ is investigated by means of shell model calculations. The basic features of the even-even and odd-odd nuclei under consideration are nicely reproduced. A sudden jump of nucleons into the upper $g_{9/2}d_{5/2}$ shell at $N=Z=36$ is found to be the main reason that causes the qualitative structure difference. It is argued that the structure change can be viewed as a decisive change of the mean field, or a phase transition, along the $N=Z$ line.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

A new type of carbon resistance thermometer with excellent thermal contact at millikelvin temperatures

Using a new brand of commercially available carbon resistor we built a cryogenic thermometer with an extremely good thermal contact to its thermal environment. Because of its superior thermal contact the thermometer is insensitive to low levels of spurious radio frequency heating. We calibrated our thermometer down to 5mK using a quartz tuning fork He-3 viscometer and measured its thermal resistance and thermal response time.Comment: 5 pages, 4 figure

Continuum quasiparticle random phase approximation and the time dependent Hartree-Fock-Bogoliubov approach

Quadrupole excitations of neutron-rich nuclei are analyzed by using the linear response method in the Quasiparticle Random Phase Approximation (QRPA). The QRPA response is derived starting from the time-dependent Hartree-Fock-Bogoliubov (HFB) equations. The residual interaction between the quasiparticles is determined consistently from the two-body force used in the HFB equations, and the continuum coupling is treated exactly. Calculations are done for the neutron-rich oxygen isotopes. It is found that pairing correlations affect the low-lying states, and that a full treatment of the continuum can change the structure of the states in the giant resonance region.Comment: 17 pages, 7 figures. Revised version with comments and references adde

SUSY signals at HERA in the no-scale flipped SU(5) supergravity model

Sparticle production and detection at HERA are studied within the recently proposed no-scale flipped $SU(5)$ supergravity model. Among the various reaction channels that could lead to sparticle production at HERA, only the following are within its limit of sensitivity in this model: $e^-p\to \tilde e^-_{L,R}\chi^0_i+X, \tilde \nu_e\chi^-_1+X$, where $\chi^0_i(i=1,2)$ are the two lightest neutralinos and $\chi^-_1$ is the lightest chargino. We study the elastic and deep-inelastic contributions to the cross sections using the Weizs\"acker-Williams approximation. We find that the most promising supersymmetric production channel is right-handed selectron ($\tilde e_{R}$) plus first neutralino ($\chi^0_1$), with one hard electron and missing energy signature. The $\tilde\nu_e\chi^-_1$ channel leads to comparable rates but also allows jet final states. A right-handedly polarized electron beam at HERA would shut off the latter channel and allow preferentially the former one. With an integrated luminosity of {\cal L}=100\ipb, HERA can extend the present LEPI lower bounds on $m_{\tilde e_R}, m_{\tilde\nu_e},m_{\chi^0_1}$ by \approx25\GeV, while {\cal L}=1000\ipb will make HERA competitive with LEPII. We also show that the Leading Proton Spectrometer (LPS) at HERA is an excellent supersymmetry detector which can provide indirect information about the sparticle masses by measuring the leading proton longitudinal momentum distribution.Comment: 11 pages, 8 figures (available upon request as uuencoded file or separate ps files), tex (harvmac) CTP-TAMU-15/93, CERN/LAA/93-1

Gravitational-wave astronomy: the high-frequency window

This contribution is divided in two parts. The first part provides a text-book level introduction to gravitational radiation. The key concepts required for a discussion of gravitational-wave physics are introduced. In particular, the quadrupole formula is applied to the anticipated ``bread-and-butter'' source for detectors like LIGO, GEO600, EGO and TAMA300: inspiralling compact binaries. The second part provides a brief review of high frequency gravitational waves. In the frequency range above (say) 100Hz, gravitational collapse, rotational instabilities and oscillations of the remnant compact objects are potentially important sources of gravitational waves. Significant and unique information concerning the various stages of collapse, the evolution of protoneutron stars and the details of the supranuclear equation of state of such objects can be drawn from careful study of the gravitational-wave signal. As the amount of exciting physics one may be able to study via the detections of gravitational waves from these sources is truly inspiring, there is strong motivation for the development of future generations of ground based detectors sensitive in the range from hundreds of Hz to several kHz.Comment: 21 pages, 5 figures, Lectures presented at the 2nd Aegean Summer School on the Early Universe, Syros, Greece, September 200

How Noisy Does a Noisy Miner Have to Be? Amplitude Adjustments of Alarm Calls in an Avian Urban ‘Adapter’

Background: Urban environments generate constant loud noise, which creates a formidable challenge for many animals relying on acoustic communication. Some birds make vocal adjustments that reduce auditory masking by altering, for example, the frequency (kHz) or timing of vocalizations. Another adjustment, well documented for birds under laboratory and natural field conditions, is a noise level-dependent change in sound signal amplitude (the ‘Lombard effect’). To date, however, field research on amplitude adjustments in urban environments has focused exclusively on bird song. Methods: We investigated amplitude regulation of alarm calls using, as our model, a successful urban ‘adapter ’ species, the Noisy miner, Manorina melanocephala. We compared several different alarm calls under contrasting noise conditions. Results: Individuals at noisier locations (arterial roads) alarm called significantly more loudly than those at quieter locations (residential streets). Other mechanisms known to improve sound signal transmission in ‘noise’, namely use of higher perches and in-flight calling, did not differ between site types. Intriguingly, the observed preferential use of different alarm calls by Noisy miners inhabiting arterial roads and residential streets was unlikely to have constituted a vocal modification made in response to sound-masking in the urban environment because the calls involved fell within the main frequency range of background anthropogenic noise. Conclusions: The results of our study suggest that a species, which has the ability to adjust the amplitude of its signals

Thermal diffusivity and Biot number: a new experimental method

A new simple method is presented for measuring thermal diffusivity and Biot number in cylindrical samples made of relatively highly conducting materials, subjected to laminar air flow. The basic idea is a heat source in the middle section of the sample, acting also as a thermocouple; only one additional temperature sensor at the cylinder basis is required to give all information, without requiring any hypothesis about the effective time dependence of the heat source