841 research outputs found
Statistical features of the thermal neutron capture cross sections
We discuss the existence of huge thermal neutron capture cross sections in
several nuclei. The values of the cross sections are several orders of
magnitude bigger than expected at these very low energies. We lend support to
the idea that this phenomenon is random in nature and is similar to what we
have learned from the study of parity violation in the actinide region. The
idea of statistical doorways is advanced as a unified concept in the
delineation of large numbers in the nuclear world. The average number of maxima
per unit mass, in the capture cross section is calculated and related
to the underlying cross section correlation function and found to be , where is a characteristic mass
correlation width which designates the degree of remnant coherence in the
system. We trace this coherence to nucleosynthesis which produced the nuclei
whose neutron capture cross sections are considered here.Comment: 7 pages, 6 figures. To appear in Acta Physica Polonica B as a
Contribution to the proceedings of:Jagiellonian Symposium of Fundamental and
Applied Subatomic Physics, June 7- 12, 2015 Krakow, Polan
An equations-of-motion approach to quantum mechanics: application to a model phase transition
We present a generalized equations-of-motion method that efficiently
calculates energy spectra and matrix elements for algebraic models. The method
is applied to a 5-dimensional quartic oscillator that exhibits a quantum phase
transition between vibrational and rotational phases. For certain parameters,
10 by 10 matrices give better results than obtained by diagonalising 1000 by
1000 matrices.Comment: 4 pages, 1 figur
A Complex Chemical Potential: Signature of Decay in a Bose-Einstein Condensate
We explore the zero-temperature statics of an atomic Bose-Einstein condensate
in which a Feshbach resonance creates a coupling to a second condensate
component of quasi-bound molecules. Using a variational procedure to find the
equation of state, the appearance of this binding is manifest in a collapsing
ground state, where only the molecular condensate is present up to some
critical density. Further, an excited state is seen to reproduce the usual
low-density atomic condensate behavior in this system, but the molecular
component is found to produce an underlying decay, quantified by the imaginary
part of the chemical potential. Most importantly, the unique decay rate
dependencies on density () and on scattering length () can be measured in experimental tests of this theory.Comment: 4 pages, 1 figur
Fine Structure Discussion of Parity-Nonconserving Neutron Scattering at Epithermal Energies
The large magnitude and the sign correlation effect in the parity
non-conserving resonant scattering of epithermal neutrons from Th is
discussed in terms of a non-collective local doorway model. General
conclusions are drawn as to the probability of finding large parity violation
effects in other regions of the periodic table.Comment: 6 pages, Tex. CTP# 2296, to appear in Z. Phys.
Right ventricular thrombus in a 36-year-old man with Factor v Leiden
Factor V Leiden deficiency is the most common hereditary hypercoagulable disease in the United States and involves 5 of the Caucasian population. Up to 30 of patients who present with deep vein thrombosis (DVT) or pulmonary thromboembolism present with this condition. This is a case report of a 36-year-old man who experienced one episode of DVT within the previous year and was admitted to our hospital due to productive coughs and hemoptysis. Paraclinical studies demonstrated a right ventricular thrombus. Additional investigation was done to find the underlying cause. Laboratory tests were positive for Factor V Leiden mutation. Other factors for hypercoagulability states were normal. Given that Factor V Leiden mutation is a life-threatening condition with a relatively high prevalence and considering its thrombogenesis, screening tests are necessary in young patients without obvious reasons for recurrent thrombus formation. It seems that medical noninvasive treatments can be an alternative therapy to surgery when a ventricular thrombus is suspected in these patients. � 2015 Tehran Heart Center. All rights reserved
Ultracold molecules: vehicles to scalable quantum information processing
We describe a novel scheme to implement scalable quantum information
processing using Li-Cs molecular state to entangle Li and Cs
ultracold atoms held in independent optical lattices. The Li atoms will
act as quantum bits to store information, and Cs atoms will serve as
messenger bits that aid in quantum gate operations and mediate entanglement
between distant qubit atoms. Each atomic species is held in a separate optical
lattice and the atoms can be overlapped by translating the lattices with
respect to each other. When the messenger and qubit atoms are overlapped,
targeted single spin operations and entangling operations can be performed by
coupling the atomic states to a molecular state with radio-frequency pulses. By
controlling the frequency and duration of the radio-frequency pulses,
entanglement can either be created or swapped between a qubit messenger pair.
We estimate operation fidelities for entangling two distant qubits and discuss
scalability of this scheme and constraints on the optical lattice lasers
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