Xiaoguang Wu

Bio: Xiaoguang Wu is an academic researcher from Jilin University. The author has contributed to research in topics: Yrast & Spin states. The author has an hindex of 8, co-authored 47 publications receiving 382 citations.

High-spin yrast and yrare structures in 112In

Abstract: The high-spin states of 112In have been investigated with in-beam \( \gamma\) -ray spectroscopic methods using the 110Pd (7Li, 5n)112In reaction at a beam energy of 50MeV. A level scheme with 3 band structures has been established. The backbending associated with the alignment of a pair of g7/2/d5/2 neutrons has been found in the negative-parity yrast band. The configuration for the positive-parity yrare band has been assigned to \( \pi\)g9/2 ⊗ \( u\)g7/2 for the lower-spin states, and \( \pi\)g9/2 ⊗ \( u\)h211/2(g7/2) for the higher-spin levels.

Superdeformed triaxial band in 167 Lu

Abstract: A new rotational band has been observed in 167Lu by 152Sm (19F,4n)reaction at the HI-13 tandem accelerator of CIAE in Beijing. The high spin transition energies of the new band are almost identical to the triaxial superdeformed bands recently discovered in 163Lu and 165Lu. This new band is predicted as a triaxial superdeformed band by total routhian surface calculations.

Candidate chiral doublet bands in Pm 138

Abstract: High-spin states of $^{138}\mathrm{Pm}$ have been populated using the $^{124}\mathrm{Te}(^{19}\mathrm{F},\phantom{\rule{0.28em}{0ex}}5\mathrm{n})^{138}\mathrm{Pm}$ reaction at a beam energy of 105 MeV. A new positive-parity side band with the same $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{ u}{h}_{11/2}$ configuration as that of the yrast band is observed in $^{138}\mathrm{Pm}$. The properties of the two positive-parity bands show general agreement with the fingerprints of chiral rotation and thus these two bands are suggested to be candidates for near degenerate chiral doublet bands. Besides, odd-even spin staggering of the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{ u}{h}_{11/2}$ bands is studied systematically in odd-odd Cs, La, Pr, and Pm isotopes. As a result of this study we suggest that the spin value of lowest observed state of the yrast band be reassigned as 9 in $^{138}\mathrm{Pm}$. This new spin assignment is also supported by the argument of alignment additivity.

Multiphonon γ-vibrational bands in the γ-soft nucleus 138 Nd

Abstract: The low spin states of ${}^{138}$Nd have been reinvestigated via the ${}^{124}$Te(${}^{19}$F,$4n1p$) reaction at a beam energy of 103 MeV. The quasi-one-phonon $\ensuremath{\gamma}$-vibrational band based on the 1013.7 keV level has been expanded and the quasi-two-phonon $\ensuremath{\gamma}$-vibrational band built on the 1842.7 keV level has been proposed. A systematic comparison supports our assignments for multiphonon $\ensuremath{\gamma}$-vibrational bands in ${}^{138}$Nd. The characteristics of $\ensuremath{\gamma}$ softness in ${}^{138}$Nd have been discussed. Triaxial projected shell model calculations can well describe the rotational feature of the bands, but they fail to reproduce simultaneously the bandhead energies of the two $\ensuremath{\gamma}$-vibrational bands if a fixed triaxial deformation is assumed.

Candidate chiral doublet bands in 128 La

Abstract: The candidate chiral doublet bands in ${}^{128}$La have been searched for through the ${}^{118}$Sn(${}^{14}$N, 4n)${}^{128}$La reaction at a beam energy of 69 MeV. A positive-parity sideband with the same configuration as that of the yrast band has been identified. The positive-parity and spins of the sideband have been assigned based on the $\ensuremath{\Delta}I=1$ mixed $M1/E2$ and $E2$ characters of the linking transitions between the sideband and the yrast band. The properties of the sideband and the yrast band are discussed. The newly identified sideband and the yrast band are suggested to form the candidate of the near degenerate chiral doublet bands.

Phase space representation of quantum dynamics

Abstract: We discuss a phase space representation of quantum dynamics of systems with many degrees of freedom. This representation is based on a perturbative expansion in quantum fluctuations around one of the classical limits. We explicitly analyze expansions around three such limits: (i) corpuscular or Newtonian limit in the coordinate-momentum representation, (ii) wave or Gross-Pitaevskii limit for interacting bosons in the coherent state representation, and (iii) Bloch limit for the spin systems. We discuss both the semiclassical (truncated Wigner) approximation and further quantum corrections appearing in the form of either stochastic quantum jumps along the classical trajectories or the nonlinear response to such jumps. We also discuss how quantum jumps naturally emerge in the analysis of non-equal time correlation functions. This representation of quantum dynamics is closely related to the phase space methods based on the Wigner-Weyl quantization and to the Keldysh technique. We show how such concepts as the Wigner function, Weyl symbol, Moyal product, Bopp operators, and others automatically emerge from the Feynmann's path integral representation of the evolution in the Heisenberg representation. We illustrate the applicability of this expansion with various examples mostly in the context of cold atom systems including sine-Gordon model, one- and two-dimensional Bose Hubbard model, Dicke model and others.

Wobbling phonon excitations in strongly deformed triaxial nuclei

Abstract: The wobbling mode is uniquely related to triaxiality and introduces a series of bands with increasing wobbling phonon number, $n_{\rm w}$ . The pattern of $\gamma$ -transitions between the wobbling excitations will be influenced by the presence of an aligned particle. Evidence for the wobbling mode was obtained recently, and even a two-phonon wobbling excitation has now been identified in 163 Lu. The similarity of the data in 163 Lu to new strongly deformed triaxial bands and connecting transitions in the neighbouring nuclei, 165 Lu and 167 Lu, establishes wobbling as a more general phenomenon in this region. The higher phonon wobbling excitations show some anharmonicity, but the characteristic large $\Delta n_{\rm w} = 1$ E2 strength is observed. The wobbling interpretation is based on the comparison of electromagnetic decay strength between bands to particle-rotor calculations in which an i 13/2 proton is coupled to a triaxial core.

Effective action in a higher-spin background

Abstract: We consider a free massless scalar field coupled to an infinite tower of background higher-spin gauge fields via minimal coupling to the traceless conserved currents. The set of Abelian gauge transformations is deformed to the non-Abelian group of unitary operators acting on the scalar field. The gauge invariant effective action is computed perturbatively in the external fields. The structure of the various (divergent or finite) terms is determined. In particular, the quadratic part of the logarithmically divergent (or of the finite) term is expressed in terms of curvatures and related to conformal higher-spin gravity. The generalized higher-spin Weyl anomalies are also determined. The relation with the theory of interacting higher-spin gauge fields on anti de Sitter spacetime via the holographic correspondence is discussed.