13,528 research outputs found
Energy Spectrum and Phase Transition of Superfluid Fermi Gas of Atoms on Noncommutative Space
Based on the Bogoliubov non-ideal gas model, we discuss the energy spectrum
and phase transition of the superfluid Fermi gas of atoms with a weak
attractive interaction on the canonical noncommutative space. Because the
interaction of a BCS-type superfluid Fermi gas originates from a pair of
Fermionic quasi-particles with opposite momenta and spins, the Hamiltonian of
the Fermi gas on the noncommutative space can be described in terms of the
ordinary creation and annihilation operators related to the commutative space,
while the noncommutative effect appears only in the coefficients of the
interacting Hamiltonian. As a result, we can rigorously solve the energy
spectrum of the Fermi gas on the noncommutative space exactly following the way
adopted on the commutative space without the use of perturbation theory. In
particular, different from the previous results on the noncommutative
degenerate electron gas and superconductor where only the first order
corrections of the ground state energy level and energy gap were derived, we
obtain the nonperturbative energy spectrum for the noncommutative superfluid
Fermi gas, and find that each energy level contains a corrected factor of
cosine function of noncommutative parameters. In addition, our result shows
that the energy gap becomes narrow and the critical temperature of phase
transition from a superfluid state to an ordinary fluid state decreases when
compared with that in the commutative case
Analysis of the scalar, axialvector, vector, tensor doubly charmed tetraquark states with QCD sum rules
In this article, we construct the axialvector-diquark-axialvector-antidiquark
type currents to interpolate the scalar, axialvector, vector, tensor doubly
charmed tetraquark states, and study them with QCD sum rules systematically by
carrying out the operator product expansion up to the vacuum condensates of
dimension 10 in a consistent way, the predicted masses can be confronted to the
experimental data in the future. We can search for those doubly charmed
tetraquark states in the Okubo-Zweig-Iizuka super-allowed strong decays to the
charmed meson pairs.Comment: 23 pages, 29 figures. arXiv admin note: substantial text overlap with
arXiv:1708.0454
Radially Excited States of
In the framework of chiral quark model, the mass spectrum of is studied with Gaussian expansion method. With the wave functions
obtained in the study of mass spectrum, the open flavor two-body strong decay
widths are calculated by using model. The results show that the masses
of and are consistent with the experimental data. The
explanation of X(3940) as is disfavored for X(3940) is a narrow
state, MeV, while the open flavor two-body
strong decay width of is about 200 MeV in our calculation.
Although the mass of X(4160) is about 100 MeV less than that of ,
the assignment of X(4160) as can not be excluded because the open
flavor two-body strong decay width of is consistent with the
experimental value of X(4160) and the branching ratios of are
compatible with that of X(4160), and the mass of can be shifted
downwards by taking into account the coupling effect of the open charm
channels. There are still no good candidates to and .Comment: 5 page
Cloning and expression of first gene for biodegrading microcystins by Sphingopyxis sp. USTB-05
Harmful cyanobacterial blooms (HCBs) in natural waters are a growing environmental problem worldwide because microcystins (MCs) produced by cyanobacteria are potent hepatotoxins and tumor promoters. MCs are resistant against physical and chemical factors. Thus, biodegradation is the most efficient method for removing MCs, and a number of bacterial strains, especially genus _Sphingomonas_, have been isolated for biodegrading MCs. Although the pathway, enzyme, and gene for biodegrading MCs by _Sphingomonas sp._ have been widely identified recently, no gene concerned with the biodegradation of MCs has been successfully cloned and expressed. In this study, we show that the first and most important gene of mlrA, containing 1,008 bp nucleotides in length, in the biodegradation pathway of MCs by _Sphingopyxis sp._ USTB-05, which encodes an enzyme MlrA containing 336 amino acid residues, is firstly cloned and expressed in _E. coli_ DH5α, with a cloning vector of pGEM-T easy and an expression vector of pGEX-4T-1. The encoded and expressed enzyme MlrA is responsible for cleaving the target peptide bond between 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-deca-4,6-dienoic acid (Adda) and Arg in the cyclic structure of microcystin-RR (MC-RR)and microcystin-LR(MC-LR), two typical and toxic types of MCs. Linear MC-RR and MC-LR are produced as the first products. These findings are important in constructing a new genetic bacterial strain for the efficient removal of MCs from the important water supplies and resolving the controversy on the biodegradation pathway of different types of MCs by genus _Sphingomonas_
Revisit assignments of the new excited states with QCD sum rules
In this article, we distinguish the contributions of the positive parity and
negative parity states, study the masses and pole residues of the
1S, 1P, 2S and 2P states with the spin and
using the QCD sum rules in a consistent way, and revisit the
assignments of the new narrow excited states. The predictions
support assigning the to be the 1P state with
, assigning the to be the 1P
state with or the 2S state with
, and assigning to be the 2S
state with .Comment: 19 pages, 22 figures. arXiv admin note: text overlap with
arXiv:1705.0774
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