665 research outputs found
Spreading widths of giant resonances in spherical nuclei: damped transient response
We propose the universal approach to describe spreading widths of monopole,
dipole and quadrupole giant resonances in heavy and superheavy spherical
nuclei. Our approach is based on the ideas of the random matrix distribution of
the coupling between one-phonon and two-phonon states generated in the random
phase approximation. We use the Skyrme interaction SLy4 as our model
Hamiltonian to create a single-particle spectrum and to analyze excited states
of the doubly magic nuclei Sn, Pb and 126. Our results
demonstrate that the universal approach enables to describe gross structure of
the spreading widths of the considered giant resonances.Comment: 6 pages, 2 figure
Two-phonon structures for beta-decay theory
The -decay rates of Ca have been studied within a microscopic
model, which is based on the Skyrme interaction T45 to construct
single-particle and phonon spaces. We observe a redistribution of the
Gamow-Teller strength due to the phonon-phonon coupling, considered in the
model. For Sc, the spin-parity of the ground state is found to be .
We predict that the half-life of Ca is 0.3 ms, while the total
probability of the emission is 6.1%. Additionally, the random
matrix theory has been applied to analyse the statistical properties of the
spectrum populated in the -decay to elucidate the obtained
results.Comment: 4 pages, 1 figure, proceedings of International Conference on Nuclear
Structure and Related Topics (NSRT18), June 3-9 2018, Burgas, Bulgari
Noncyclic geometric changes of quantum states
Non-Abelian quantum holonomies, i.e., unitary state changes solely induced by
geometric properties of a quantum system, have been much under focus in the
physics community as generalizations of the Abelian Berry phase. Apart from
being a general phenomenon displayed in various subfields of quantum physics,
the use of holonomies has lately been suggested as a robust technique to obtain
quantum gates; the building blocks of quantum computers. Non-Abelian holonomies
are usually associated with cyclic changes of quantum systems, but here we
consider a generalization to noncyclic evolutions. We argue that this open-path
holonomy can be used to construct quantum gates. We also show that a structure
of partially defined holonomies emerges from the open-path holonomy. This
structure has no counterpart in the Abelian setting. We illustrate the general
ideas using an example that may be accessible to tests in various physical
systems.Comment: Extended version, new title, journal reference adde
Microscopic Origin of Quantum Chaos in Rotational Damping
The rotational spectrum of Yb is calculated diagonalizing different
effective interactions within the basis of unperturbed rotational bands
provided by the cranked shell model. A transition between order and chaos
taking place in the energy region between 1 and 2 MeV above the yrast line is
observed, associated with the onset of rotational damping. It can be related to
the higher multipole components of the force acting among the unperturbed
rotational bands.Comment: 7 pages, plain TEX, YITP/K-99
Supershell structure in trapped dilute Fermi gases
We show that a dilute harmonically trapped two-component gas of fermionic
atoms with a weak repulsive interaction has a pronounced super-shell structure:
the shell fillings due to the spherical harmonic trapping potential are
modulated by a beat mode. This changes the ``magic numbers'' occurring between
the beat nodes by half a period. The length and amplitude of this beating mode
depend on the strength of the interaction. We give a simple interpretation of
the beat structure in terms of a semiclassical trace formula for the symmetry
breaking U(3) --> SO(3).Comment: 4 pages, 4 figures; In version 2, references added. The semiclassical
explanation of super-shell structure is refined. Version 3, as appeared in
Phys. Rev.
Further experiments with the Iowa air blast seed separator for the analysis of small-seeded grasses
In recent years attempts, have been made in Europe and North America to improve seed laboratory machines used for the separation of chaff from heavy seeds in grasses. The most important European contribution is probably the Gilchrist seed separator used at the seed testing station in Edinburgh, Scotland. The Holland (Leendertz) separator has some merit, but its chief weakness as shown by Porter (7) was the inconstant speed of the motor which made it. impossible to deliver the same volume of air through the separator tube each time the valve was opened to a given point. Replacement of the motor by one that operated at constant speed was found by Brown and Porter (1) to correct the defect reasonably well. The use of bolting cloth in place of a metal screen is also a disadvantage. Following the initial work Porter (8) described a new seed separator equipped with a combined motor\u27 and fan unit of standard specifications which made uniform separations of bluegrass, redtop and orchard grass samples either by repeated blowings of the same sub-sample or by a single blowing for each of many replicate sub-samples. He also employed synthetic samples to check the accuracy and uniformity of separation. These results were obtained with samples from the same lot and indicated that for any given lot of seed it was possible to obtain uniform results if care was used in reading the dial opening on the valve or the manometer which indicated pressure in the compression chamber. It is noteworthy that in his experiments Porter (8) showed that if the weight of sample varied from 112 to 2 grams of blue-\u27 grass seed, the dial reading was more dependable than pressure as measured in the compression chamber, and further that pressure as measured in the blowing tube was about as reliable as the dial reading. He showed, however, that with samples having a low weight per bushel the amount of germinable seed removed at a given opening was greater than with samples having a high weight per bushel
Adiabatic Approximation for weakly open systems
We generalize the adiabatic approximation to the case of open quantum
systems, in the joint limit of slow change and weak open system disturbances.
We show that the approximation is ``physically reasonable'' as under wide
conditions it leads to a completely positive evolution, if the original master
equation can be written on a time-dependent Lindblad form. We demonstrate the
approximation for a non-Abelian holonomic implementation of the Hadamard gate,
disturbed by a decoherence process. We compare the resulting approximate
evolution with numerical simulations of the exact equation.Comment: New material added, references added and updated, journal reference
adde
The Presence of Norovirus and Adenovirus on Environmental Surfaces in Relation to the Hygienic Level in Food Service Operations Associated with a Suspected Gastroenteritis Outbreak
Erratum: Food and environmental virology 9 (2017):3, pp. 358-359 DOI.10.1007/s12560-017-9304-6Norovirus (NoV) gastroenteritis outbreaks appear frequently in food service operations (FSOs), such as in restaurants and canteens. In this study the presence of NoV and adenovirus (AdV) genomes was investigated on the surfaces of premises, especially in kitchens, of 30 FSOs where foodborne gastroenteritis outbreaks were suspected. The objective was to establish a possible association between the presence of virus genomes on surfaces and a visual hygienic status of the FSOs. NoV genome was found in 11 and AdV genome in 8 out of 30 FSOs. In total, 291 swabs were taken, of which 8.9% contained NoV and 5.8% AdV genome. The presence of NoV genomes on the surfaces was not found to associate with lower hygiene level of the premises when based on visual inspection; most (7/9) of the FSOs with NoV contamination on surfaces and a completed evaluation form had a good hygiene level (the best category). Restaurants had a significantly lower proportion of NoV-positive swabs compared to other FSOs (canteens, cafeteria, schools etc.) taken together (p = 0.00014). The presence of a designated break room for the workers was found to be significantly more common in AdV-negative kitchens (p = 0.046). Our findings suggest that swabbing is necessary for revealing viral contamination of surfaces and emphasis of hygiene inspections should be on the food handling procedures, and the education of food workers on virus transmission.Peer reviewe
Simple model for decay of superdeformed nuclei
Recent theoretical investigations of the decay mechanism out of a
superdeformed nuclear band have yielded qualitatively different results,
depending on the relative values of the relevant decay widths. We present a
simple two-level model for the dynamics of the tunneling between the
superdeformed and normal-deformed bands, which treats decay and tunneling
processes on an equal footing. The previous theoretical results are shown to
correspond to coherent and incoherent limits of the full tunneling dynamics.
Our model accounts for experimental data in both the A~150 mass region, where
the tunneling dynamics is coherent, and in the A~190 mass region, where the
tunneling dynamics is incoherent.Comment: 4 page
Toward physical realizations of thermodynamic resource theories
Conventional statistical mechanics describes large systems and averages over
many particles or over many trials. But work, heat, and entropy impact the
small scales that experimentalists can increasingly control, e.g., in
single-molecule experiments. The statistical mechanics of small scales has been
quantified with two toolkits developed in quantum information theory: resource
theories and one-shot information theory. The field has boomed recently, but
the theorems amassed have hardly impacted experiments. Can thermodynamic
resource theories be realized experimentally? Via what steps can we shift the
theory toward physical realizations? Should we care? I present eleven
opportunities in physically realizing thermodynamic resource theories.Comment: Publication information added. Cosmetic change
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