Coherent States with SU(N) Charges

We define coherent states carrying SU(N) charges by exploiting generalized Schwinger boson representation of SU(N) Lie algebra. These coherent states are defined on $2 (2^{N - 1} - 1)$ complex planes. They satisfy continuity property and provide resolution of identity. We also exploit this technique to construct the corresponding non-linear SU(N) coherent states.Comment: 18 pages, LaTex, no figure

Method of Collective Degrees of Freedom in Spin Coherent State Path Integral

We present a detailed field theoretic description of those collective degrees of freedom (CDF) which are relevant to study macroscopic quantum dynamics of a quasi-one-dimensional ferromagnetic domain wall. We apply spin coherent state path integral (SCSPI) in the proper discrete time formalism (a) to extract the relevant CDF's, namely, the center position and the chirality of the domain wall, which originate from the translation and the rotation invariances of the system in question, and (b) to derive effective action for the CDF's by elimination of environmental zero-modes with the help of the {\it Faddeev-Popov technique}. The resulting effective action turns out to be such that both the center position and the chirality can be formally described by boson coherent state path integral. However, this is only formal; there is a subtle departure from the latter.Comment: 10 pages, 1 figur

An ultra-deep multi-band VLA survey of the faint radio sky (COSMOS-XS): New constraints on the cosmic star formation history

We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array observations of the COSMOS field from the multi-band COSMOS-XS survey to infer radio luminosity functions (LFs) of star-forming galaxies (SFGs). Using $\sim$1300 SFGs with redshifts out to $z\sim4.6$, and fixing the faint and bright end shape of the radio LF to the local values, we find a strong redshift trend that can be fitted by pure luminosity evolution with the luminosity parameter given by $\alpha_L \propto (3.40 \pm 0.11) - (0.48 \pm 0.06)z$. We then combine the ultra-deep COSMOS-XS data-set with the shallower VLA-COSMOS $\mathrm{3\,GHz}$ large project data-set over the wider COSMOS field in order to fit for joint density+luminosity evolution, finding evidence for significant density evolution. By comparing the radio LFs to the observed far-infrared (FIR) and ultraviolet (UV) LFs, we find evidence of a significant underestimation of the UV LF by $21.6\%\, \pm \, 14.3 \, \%$ at high redshift ($3.3\,<\,z\,<\,4.6$, integrated down to $0.03\,L^{\star}_{z=3}$). We derive the cosmic star formation rate density (SFRD) by integrating the fitted radio LFs and find that the SFRD rises up to $z\,\sim\,1.8$ and then declines more rapidly than previous radio-based estimates. A direct comparison between the radio SFRD and a recent UV-based SFRD, where we integrate both LFs down to a consistent limit ($0.038\,L^{\star}_{z=3}$), reveals that the discrepancy between the radio and UV LFs translates to a significant ($\sim$1 dex) discrepancy in the derived SFRD at $z>3$, even assuming the latest dust corrections and without accounting for optically dark sources.Comment: Submitted to ApJ; 27 pages, 13 figures, 4 table

Changes in characteristics and outcomes of patients undergoing surgery for hip fractures following the initiation of orthogeriatric service:Temporal trend analysis

The Blue Book published by the British Orthopaedic Association and British Geriatrics Society, together with the introduction of National Hip Fracture Database Audit and Best Practice Tariff, have been influential in improving hip fracture care. We examined ten-year (2009–2019) changes in hip fracture outcomes after establishing an orthogeriatric service based on these initiatives, in 1081 men and 2891 women (mean age = 83.5 ± 9.1 years). Temporal trends in the annual percentage change (APC) of outcomes were identified using the Joinpoint Regression Program v4.7.0.0. The proportions of patients operated beyond 36 h of admission fell sharply during the first two years: APC =  − 53.7% (95% CI − 68.3, − 5.2, P = 0.003), followed by a small rise thereafter: APC = 5.8% (95% CI 0.5, 11.3, P = 0.036). Hip surgery increased progressively in patients > 90 years old: APC = 3.3 (95% CI 1.0, 5.8, P = 0.011) and those with American Society of Anaesthesiologists grade ≥ 3: APC = 12.4 (95% CI 8.8, 16.1, P  90 years old: APC =  − 7.1 (95% CI − 12.6, − 1.3, P = 0.024). Prolonged length of stay (> 23 days) declined from 2013: APC =  − 24.6% (95% CI − 31.2, − 17.4, P < 0.001). New discharge to nursing care declined moderately over 2009–2016 (APC =  − 10.6, 95% CI − 17.2, − 2.7, P = 0.017) and sharply thereafter (APC =  − 47.5%, 95%CI − 71.7, − 2.7, P = 0.043). The rate of patients returning home was decreasing (APC =  − 2.9, 95% CI − 5.1, − 0.7, P = 0.016), whilst new discharge to rehabilitation was increasing (APC = 8.4, 95% CI 4.0, 13.0; P = 0.002). In conclusion, the establishment of an orthogeriatric service was associated with a reduction of elapsed time to hip surgery, a progressive increase in surgery carried out on high-risk adults and a decline in adverse outcomes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00223-021-00906-4

Geometric approach to nonlinear coherent states using the Higgs model for harmonic oscillator

In this paper, we investigate the relation between the curvature of the physical space and the deformation function of the deformed oscillator algebra using non-linear coherent states approach. For this purpose, we study two-dimensional harmonic oscillators on the flat surface and on a sphere by applying the Higgs modell. With the use of their algebras, we show that the two-dimensional oscillator algebra on a surface can be considered as a deformed one-dimensional oscillator algebra where the effect of the curvature of the surface is appeared as a deformation function. We also show that the curvature of the physical space plays the role of deformation parameter. Then we construct the associated coherent states on the flat surface and on a sphere and compare their quantum statistical properties, including quadrature squeezing and antibunching effect.Comment: 12 pages, 7 figs. To be appeared in J. Phys.

Coherent pairing states for the Hubbard model

We consider the Hubbard model and its extensions on bipartite lattices. We define a dynamical group based on the $\eta$-pairing operators introduced by C.N.Yang, and define coherent pairing states, which are combinations of eigenfunctions of $\eta$-operators. These states permit exact calculations of numerous physical properties of the system, including energy, various fluctuations and correlation functions, including pairing ODLRO to all orders. This approach is complementary to BCS, in that these are superconducting coherent states associated with the exact model, although they are not eigenstates of the Hamiltonian.Comment: 5 pages, RevTe