Bose-Einstein condensate in a rapidly rotating non-symmetric trap

A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional harmonic trap can be described with the lowest Landau-level set of single-particle states. The condensate wave function psi(x,y) is a Gaussian exp(-r^2/2), multiplied by an analytic function f(z) of the complex variable z= x+ i y. The criterion for a quantum phase transition to a non-superfluid correlated many-body state is usually expressed in terms of the ratio of the number of particles to the number of vortices. Here, a similar description applies to a rapidly rotating non-symmetric two-dimensional trap with arbitrary quadratic anisotropy (omega_x^2 < omega_y^2). The corresponding condensate wave function psi(x,y) is a complex anisotropic Gaussian with a phase proportional to xy, multiplied by an analytic function f(z), where z = x + i \beta_- y is a stretched complex variable and 0< \beta_- <1 is a real parameter that depends on the trap anisotropy and the rotation frequency. Both in the mean-field Thomas-Fermi approximation and in the mean-field lowest Landau level approximation with many visible vortices, an anisotropic parabolic density profile minimizes the energy. An elongated condensate grows along the soft trap direction yet ultimately shrinks along the tight trap direction. The criterion for the quantum phase transition to a correlated state is generalized (1) in terms of N/L_z, which suggests that a non-symmetric trap should make it easier to observe this transition or (2) in terms of a "fragmented" correlated state, which suggests that a non-symmetric trap should make it harder to observe this transition. An alternative scenario involves a crossover to a quasi one-dimensional condensate without visible vortices, as suggested by Aftalion et al., Phys. Rev. A 79, 011603(R) (2009).Comment: 20 page

Neutron Stars in Globular Clusters

Dynamical interactions that occur between objects in dense stellar systems are particularly important for the question of formation of X-ray binaries. We present results of numerical simulations of 70 globular clusters with different dynamical properties and a total stellar mass of 2*10^7 Msun. We find that in order to retain enough neutron stars to match observations we must assume that NSs can be formed via electron-capture supernovae. Our simulations explain the observed dependence of the number of LMXBs on ``collision number'' as well as the large scatter observed between different globular clusters. For millisecond pulsars, we obtain good agreement between our models and the numbers and characteristics of observed pulsars in the clusters Terzan 5 and 47 TucComment: 5 pages, 3 figures, to appear in "Dynamical Evolution of Dense Stellar Systems", IAUS 246, ed. E. Vesperin

Vector Area Theorem mapping in crystals and polarization stability of SIT-solitons

The stability of polarization, areas, and number of self-induced transparency (SIT)-solitons at the output from the LaF_3:Pr^{3+} crystal is theoretically studied versus the polarization direction and the area of the input linearly polarized laser pulse. For this purpose the Vector Area Theorem is rederived and two-dimensional Vector Area Theorem map is obtained. The map is governed by the crystal symmetry and takes into account directions of the dipole matrix element vectors of the different site subgroups of optically excited ions. The Vector Area Theorem mapping of the time evolution of the laser pulse allows one to highlight soliton polarization properties.Comment: 3 pages, 3 figures; v2: minor corrected labels in Fig. 3 and its cuptur

Possible attenuation of the G2 DNA damage cell cycle checkpoint in HeLa cells by extremely low frequency (ELF) electromagnetic fields

BACKGROUND: The issue remains unresolved as to whether low frequency magnetic fields can affect cell behaviour, with the possibility that they may be in part responsible for the increased incidence of leukaemia in parts of the population exposed to them. METHODS: Combined treatment of HeLa cells with gamma-irradiation (1, 3 and 5 Grays) and extra low frequency magnetic fields of ~50 Hz was carried out under rigorously controlled conditions. RESULTS: Synchronised cells progressing from S-phase arrived at mitosis on average marginally ahead of irradiation controls not exposed to ELF. In no instance out of a total of twenty separate experiments did this "double-insult" further delay entry of cells into mitosis, as had been anticipated. CONCLUSION: This apparently "non-genotoxic" agent (ELF) appears to be capable of affecting cells that would normally arrest for longer in G2, suggesting a weakening of the stringency of the late cycle (G2) checkpoint

Helical motion of magnetic flux tubes in the solar atmosphere

Photospheric granulation may excite transverse kink pulses in anchored vertical magnetic flux tubes. The pulses propagate upwards along the tubes with the kink speed, while oscillating wakes are formed behind the wave front in a stratified atmosphere. The wakes oscillate at the kink cut-off frequency of stratified medium and gradually decay in time. When two or more consecutive kink pulses with different polarizations propagate in the same thin tube, then the wakes corresponding to different pulses may superimpose. The superposition sets up helical motions of magnetic flux tubes in the photosphere/chromosphere as seen by recent Hinode movies. The energy carried by the pulses is enough to heat the solar chrmosphere/corona and accelerate the solar wind.Comment: Accepted in ApJ

Electron beam welding of copper-Monel facilitated by circular magnetic shields

High permeability, soft magnetic rings are placed on both sides of electron beam weld seams in copper-Monel circular joint. This eliminates deflection of the electron beam caused by magnetic fields present in the weld area

The Effects of Peer Connectedness and Popularity in Predicting Adolescent E-Cigarette and Binge Drinking Patterns Across the COVID-19 Pandemic

Despite research in adolescent substance use being a well-established discipline, little is known about the relationships between substance use during the COVID-19 pandemic when related to self-reported popularity and peer connectedness as predictors of this behaviour. This study sought to determine how binge drinking and vaping changed from the beginning of the pandemic (T1) to June 2021 (T2) and to examine how self-reported popularity and peer connectedness were predictors of this behaviour. At T1, there were 937 adolescent participants between 14-18 years of age (Mage = 16.93, SD = .85; 76.7% female, 21% male, and 2.3% other) and at T2, there were 489 adolescent participants (Mage = 17.96, 79.1% female, 17.6% male and 2.8% other). Participants completed online self-report surveys with questions related to their substance use frequency, peer connectedness during the pandemic and self-reported popularity at both T1 and T2. It was hypothesized that binge drinking and vaping frequency, operationalized as the number of days of use in the last three weeks, would be greater at T2 compared to T1. Furthermore, it was hypothesized that self-reported popularity and peer connectedness at T1 would predict increased substance use at T2. A paired-samples t-test revealed that adolescents binge drank and vaped more at T2 compared to T1. Stepwise linear regression revealed that T1 popularity was a significant predictor of vaping at T2 but not binge drinking at T2, although the results did not predict increases in vaping from T1 to T2. Last, the regression substantiated that increased peer connectedness at T1 did not predict increased substance use at T2. These findings suggest that adolescents may be at a greater risk negative consequences related to substance use and self-reported popularity. Implications, results for adolescent substance use, as well as prevention, intervention, and future directions are discussed

Cups as a Record of Humans: Material Culture Effects on Social Communication

Drinking vessels are a uniquely universal tool. They are used in all cultures, pertaining but not limited to ceremony, practice, practicality and custom. This thesis examines changes in ceramic cups and how this material culture reflects a collective record of human intention. My project emphasizes how the aesthetics of ceramic work is influenced by the social structures of the societies they are made into. When making pottery the ceramicist absorbs the style, history, social status, ergonomics, and intention of external stimuli that then become part of their own work. Observing pottery over time, physical changes depict a variety of human priorities and choices. These choices demonstrate what is important to a society as well as the hierarchy of who has the power to make these changes. Alongside this essay, Heirlooms, a ceramic exhibition, allows me to participate in the making of material culture by creating cups that others will experience in a first-person format. I provide small simple drinking vessels to suggest an intentional slow approach to consumption. These standards of creation are influenced by ancient Chinese cups without handles that were small in stature, as opposed to the mass consumption presentation of some modern drinking vessels. This allows me to become a part of the continued human socio-material conversation through physical agency with clay

Lowest Landau-level description of a Bose-Einstein condensate in a rapidly rotating anisotropic trap

A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional trap can be described with the lowest Landau-level set of states. In this case, the condensate wave function psi(x,y) is a Gaussian function of r^2 = x^2 + y^2, multiplied by an analytic function P(z) of the single complex variable z= x+ i y; the zeros of P(z) denote the positions of the vortices. Here, a similar description is used for a rapidly rotating anisotropic two-dimensional trap with arbitrary anisotropy (omega_x/omega_y le 1). The corresponding condensate wave function psi(x,y) has the form of a complex anisotropic Gaussian with a phase proportional to xy, multiplied by an analytic function P(zeta), where zeta is proportional to x + i beta_- y and 0 le beta_- le 1 is a real parameter that depends on the trap anisotropy and the rotation frequency. The zeros of P(zeta) again fix the locations of the vortices. Within the set of lowest Landau-level states at zero temperature, an anisotropic parabolic density profile provides an absolute minimum for the energy, with the vortex density decreasing slowly and anisotropically away from the trap center.Comment: 13 pages, 1 figur