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1.
The decay energy spectrum for neutron unbound states in 24O (Z=8Z=8, N=16N=16) has been observed for the first time. The resonance energy of the lowest lying state, interpreted as the 2+2+ level, has been observed at a decay energy above 600 keV. The resulting excitation energy of the 2+2+ level above 4.7 MeV, supplies strong evidence that 24O is a doubly magic nucleus. The data is also consistent with the presence of a second excited state around 5.33 MeV which can be interpreted as the 1+1+ level.  相似文献   

2.
Isomeric two-quasiparticle states have been identified in the neutron-rich isotopes 172Er and 174Er using multi-nucleon transfer reactions with 136Xe beams incident on various targets, and γ  -ray spectroscopy with Gammasphere. A candidate for the Kπ=6+Kπ=6+ two-quasineutron state in 172Er is found at 1500 keV. In 174Er, a nuclide whose level scheme was previously unknown, a long-lived isomer is identified at 1112 keV decaying via an inhibited E1 transition and revealing the yrast sequence of 174Er. This isomer is proposed to be a Kπ=8Kπ=8 two-quasineutron state, defining a sequence in the N=106N=106 isotones extending from the well-deformed neutron-rich isotope 174Er to the neutron-deficient isotope 188Pb, where the presence of the isomer signifies a prolate minimum in an otherwise spherical well. Configuration-constrained potential-energy surface calculations are used to predict the excitation energies of the 6+ and 8 intrinsic states and as a basis for extracting the pairing force strength, GnGn, in the N=104N=104 and N=106N=106 isotones.  相似文献   

3.
We report on direct experimental evidence of the population of the 3/23/2 intruder state in 27Ne in the knockout of a single neutron from the ground state of 28Ne. This low-lying negative parity state is consistent with a narrower shell gap for exotic nuclei with Z?NZ?N and N≈20N20. Monte Carlo shell-model calculations with the modern SDPF-M interaction successfully describe neutron-rich nuclei in the vicinity of N=20N=20 where normal and intruder configurations coexist at low excitation energy. This observation demonstrates the importance of direct reactions for the study of exotic nuclei and the predictive power of these large-scale shell-model calculations.  相似文献   

4.
We report changes in mean-square charge radii, δ〈r2δr2, magnetic moments and quadrupole moments for three multi-quasi particle isomers; 97m2Y, 176mYb and 178m1Hf. All the isomers are observed to display a decrease in 〈r2r2 compared to the lower-lying nuclear state on which the isomer is built. The decreases in 〈r2r2 occur despite the isomers showing increases in quadrupole moment. Possible mechanisms for the effect, which is now seen for six multi-quasi particle isomers, are discussed.  相似文献   

5.
A complex symplectic structure on a Lie algebra hh is an integrable complex structure JJ with a closed non-degenerate (2,0)(2,0)-form. It is determined by JJ and the real part ΩΩ of the (2,0)(2,0)-form. Suppose that hh is a semi-direct product g?Vg?V, and both gg and VV are Lagrangian with respect to ΩΩ and totally real with respect to JJ. This note shows that g?Vg?V is its own weak mirror image in the sense that the associated differential Gerstenhaber algebras controlling the extended deformations of ΩΩ and JJ are isomorphic.  相似文献   

6.
We employ chaotic (?2?2 and ?4?4) inflation to illustrate the important role radiative corrections can play during the inflationary phase. Yukawa interactions of ?  , in particular, lead to corrections of the form −κ?4ln(?/μ)κ?4ln(?/μ), where κ>0κ>0 and μ   is a renormalization scale. For instance, ?4?4 chaotic inflation with radiative corrections looks compatible with the most recent WMAP (5 year) analysis, in sharp contrast to the tree level case. We obtain the 95% confidence limits 2.4×10−14?κ?5.7×10−142.4×10−14?κ?5.7×10−14, 0.931?ns?0.9580.931?ns?0.958 and 0.038?r?0.2050.038?r?0.205, where nsns and r   respectively denote the scalar spectral index and scalar to tensor ratio. The limits for ?2?2 inflation are κ?7.7×10−15κ?7.7×10−15, 0.929?ns?0.9660.929?ns?0.966 and 0.023?r?0.1350.023?r?0.135. The next round of precision experiments should provide a more stringent test of realistic chaotic ?2?2 and ?4?4 inflation.  相似文献   

7.
To complement existing knowledge of the density matrix γF(x,y)γF(x,y) of independent fermions for N   particles in one dimension under harmonic confinement, the corresponding matrix γIB(x,y)γIB(x,y) for impenetrable bosons is given for N=2N=2 and 3 (with the N=4N=4 form available also). For fermions the momentum density is then obtained and illustrated numerically for N=10N=10. The boson momentum density is studied analytically at high momentum p  , the coefficients of the p−4p−4 and p−6p−6 terms being tabulated for N=2–5N=25 inclusive. Their dependence on powers of N   is exhibited numerically. Finally, the functional relationship between γIB(x,y)γIB(x,y) and γF(x,y)γF(x,y) is formally set out and illustrated.  相似文献   

8.
We investigate the geometry of the moduli space of NN vortices on line bundles over a closed Riemann surface ΣΣ of genus g>1g>1, in the little explored situation where 1≤N<g1N<g. In the regime where the area of the surface is just large enough to accommodate NN vortices (which we call the dissolving limit), we describe the relation between the geometry of the moduli space and the complex geometry of the Jacobian variety of ΣΣ. For N=1N=1, we show that the metric on the moduli space converges to a natural Bergman metric on ΣΣ. When N>1N>1, the vortex metric typically degenerates as the dissolving limit is approached, the degeneration occurring precisely on the critical locus of the Abel–Jacobi map of ΣΣ at degree NN. We describe consequences of this phenomenon from the point of view of multivortex dynamics.  相似文献   

9.
The cross sections for (n,x)(n,x) reactions with Ge isotopes were measured at (dt) neutron energies around 14 MeV with the activation technique using metal discs of natural composition. Calculations of detector efficiency, incident neutron spectrum and correction factors were performed with the Monte Carlo technique (MCNP4C code). Cross sections data are presented for 70Ge(n,2nn,2n)69Ge, 74Ge(n,αn,α)71mZn, 76Ge(n,2nn,2n)75(m + g)Ge, 70Ge(n,pn,p)70Ga and 72Ge(n,2nn,2n)71gGe reactions. The cross section results for 72Ge(n,2nn,2n)71gGe reaction were reported for the first time. Some other cross sections were obtained with higher precision, including the 70Ge(n,pn,p)70Ga reaction. Theoretical calculations of excitation functions were performed with the TALYS-1.0 code and compared with the experimental cross section values. Data were included in the EXFOR database.  相似文献   

10.
11.
We develop a variational approximation to the entanglement entropy for scalar ?4?4 theory in 1+11+1, 2+12+1, and 3+13+1 dimensions, and then examine the entanglement entropy as a function of the coupling. We find that in 1+11+1 and 2+12+1 dimensions, the entanglement entropy of ?4?4 theory as a function of coupling is monotonically decreasing and convex. While ?4?4 theory with positive bare coupling in 3+13+1 dimensions is thought to lead to a trivial free theory, we analyze a version of ?4?4 with infinitesimal negative bare coupling, an asymptotically free theory known as precarious  ?4?4 theory, and explore the monotonicity and convexity of its entanglement entropy as a function of coupling. Within the variational approximation, the stability of precarious ?4?4 theory is related to the sign of the first and second derivatives of the entanglement entropy with respect to the coupling.  相似文献   

12.
A curve αα immersed in the three-dimensional sphere S3S3 is said to be a Bertrand curve if there exists another curve ββ and a one-to-one correspondence between αα and ββ such that both curves have common principal normal geodesics at corresponding points. The curves αα and ββ are said to be a pair of Bertrand curves in S3S3. One of our main results is a sort of theorem for Bertrand curves in S3S3 which formally agrees with the classical one: “Bertrand curves in S3S3 correspond to curves for which there exist two constants λ≠0λ0 and μμ such that λκ+μτ=1λκ+μτ=1”, where κκ and ττ stand for the curvature and torsion of the curve; in particular, general helices in the 3-sphere introduced by M. Barros are Bertrand curves. As an easy application of the main theorem, we characterize helices in S3S3 as the only twisted curves in S3S3 having infinite Bertrand conjugate curves. We also find several relationships between Bertrand curves in S3S3 and (1,3)-Bertrand curves in R4R4.  相似文献   

13.
Two interacting, strongly-deformed triaxial (TSD) bands have been identified in the Z=69Z=69 nucleus 163Tm. This is the first time that interacting TSD bands have been observed in an element other than the Z=71Z=71 Lu nuclei, where wobbling bands have been previously identified. The observed TSD bands in 163Tm appear to be associated with particle–hole excitations, rather than wobbling. Tilted-axis cranking (TAC) calculations reproduce all experimental observables of these bands reasonably well and also provide an explanation for the presence of wobbling bands in the Lu nuclei, and their absence in the Tm isotopes.  相似文献   

14.
Even though the one-dimensional (1D) Hubbard model is solvable by the Bethe ansatz, at half-filling its finite-temperature T>0T>0 transport properties remain poorly understood. In this paper we combine that solution with symmetry to show that within that prominent T=0T=0 1D insulator the charge stiffness D(T)D(T) vanishes for T>0T>0 and finite values of the on-site repulsion UU in the thermodynamic limit. This result is exact and clarifies a long-standing open problem. It rules out that at half-filling the model is an ideal conductor in the thermodynamic limit. Whether at finite TT and U>0U>0 it is an ideal insulator or a normal resistor remains an open question. That at half-filling the charge stiffness is finite at U=0U=0 and vanishes for U>0U>0 is found to result from a general transition from a conductor to an insulator or resistor occurring at U=Uc=0U=Uc=0 for all finite temperatures T>0T>0. (At T=0T=0 such a transition is the quantum metal to Mott-Hubbard-insulator transition.) The interplay of the ηη-spin SU(2)SU(2) symmetry with the hidden U(1)U(1) symmetry beyond SO(4)SO(4) is found to play a central role in the unusual finite-temperature charge transport properties of the 1D half-filled Hubbard model.  相似文献   

15.
In [L. Lebtahi, Lie algebra on the transverse bundle of a decreasing family of foliations, J. Geom. Phys. 60 (2010), 122–133], we defined the transverse bundle VkVk to a decreasing family of kk foliations FiFi on a manifold MM. We have shown that there exists a (1,1)(1,1) tensor JJ of VkVk such that Jk≠0Jk0, Jk+1=0Jk+1=0 and we defined by LJ(Vk)LJ(Vk) the Lie Algebra of vector fields XX on VkVk such that, for each vector field YY on VkVk, [X,JY]=J[X,Y][X,JY]=J[X,Y].  相似文献   

16.
In this article we study in detail the supersymmetric structures that underlie the system of fermionic zero modes around a superconducting cosmic string. Particularly, we extend the analysis existing in the literature on the one dimensional N=2N=2 supersymmetry and we find multiple N=2N=2, d=1d=1 supersymmetries. In addition, compact perturbations of the Witten index of the system are performed and we find to which physical situations these perturbations correspond. More importantly, we demonstrate that there exists a much more rich supersymmetric structure underlying the system of fermions with NfNf flavors and these are NN-extended supersymmetric structures with non-trivial topological charges, with “NN” depending on the fermion flavors.  相似文献   

17.
We discuss three Hamiltonians, each with a central-field part H0H0 and a PT-symmetric perturbation igzigz. When H0H0 is the isotropic Harmonic oscillator the spectrum is real for all gg because HH is isospectral to H0+g2/2H0+g2/2. When H0H0 is the Hydrogen atom then infinitely many eigenvalues are complex for all gg. If the potential in H0H0 is linear in the radial variable rr then the spectrum of HH exhibits real eigenvalues for 0<g<gc0<g<gc and a PT phase transition at gcgc.  相似文献   

18.
We consider a Schrödinger differential expression L=ΔA+qL=ΔA+q on a complete Riemannian manifold (M,g)(M,g) with metric gg, where ΔAΔA is the magnetic Laplacian on MM and q≥0q0 is a locally square integrable function on MM. In the terminology of W.N. Everitt and M. Giertz, the differential expression LL is said to be separated in L2(M)L2(M) if for all u∈L2(M)uL2(M) such that Lu∈L2(M)LuL2(M), we have qu∈L2(M)quL2(M). We give sufficient conditions for LL to be separated in L2(M)L2(M).  相似文献   

19.
We discuss space-time symmetric Hamiltonian operators of the form H=H0+igHH=H0+igH, where H0H0 is Hermitian and gg real. H0H0 is invariant under the unitary operations of a point group GG while HH is invariant under transformation by elements of a subgroup GG of GG. If GG exhibits irreducible representations of dimension greater than unity, then it is possible that HH has complex eigenvalues for sufficiently small nonzero values of gg. In the particular case that HH is parity-time symmetric then it appears to exhibit real eigenvalues for all 0<g<gc0<g<gc, where gcgc is the exceptional point closest to the origin. Point-group symmetry and perturbation theory enable one to predict whether HH may exhibit real or complex eigenvalues for g>0g>0. We illustrate the main theoretical results and conclusions of this paper by means of two- and three-dimensional Hamiltonians exhibiting a variety of different point-group symmetries.  相似文献   

20.
We study integrable cases of pairing BCS hamiltonians containing several types of fermions. We prove that there exist three classes of such integrable models associated with classical rational r  -matrices and Lie algebras gl(2m)gl(2m), sp(2m)sp(2m) and so(2m)so(2m) correspondingly. We diagonalize the constructed hamiltonians by means of the algebraic Bethe ansatz. In the partial case of two types of fermions (m=2m=2) the obtained models may be interpreted as N=ZN=Z proton–neutron integrable models. In particular, in the case of sp(4)sp(4) we recover the famous integrable proton–neutron model of Richardson.  相似文献   

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