Emergent SU(N) symmetry in disordered SO(N) spin chains

Strongly disordered spin chains invariant under the SO(N) group are shown to display random-singlet phases with emergent SU(N) symmetry without fine tuning. The phases with emergent SU(N) symmetry are of two kinds: one has a ground state formed of randomly distributed singlets of strongly bound pairs of SO(N) spins (a `mesonic' phase), while the other has a ground state composed of singlets made out of strongly bound integer multiples of N SO(N) spins (a `baryonic' phase). The established mechanism is general and we put forward the cases of $\mathrm{N}=2,3,4$ and $6$ as prime candidates for experimental realizations in material compounds and cold-atoms systems. We display universal temperature scaling and critical exponents for susceptibilities distinguishing these phases and characterizing the enlarging of the microscopic symmetries at low energies.Comment: 5 pages, 2 figures, Contribution to the Topical Issue "Recent Advances in the Theory of Disordered Systems", edited by Ferenc Igl\'oi and Heiko Riege

Highly-symmetric random one-dimensional spin models

The interplay of disorder and interactions is a challenging topic of condensed matter physics, where correlations are crucial and exotic phases develop. In one spatial dimension, a particularly successful method to analyze such problems is the strong-disorder renormalization group (SDRG). This method, which is asymptotically exact in the limit of large disorder, has been successfully employed in the study of several phases of random magnetic chains. Here we develop an SDRG scheme capable to provide in-depth information on a large class of strongly disordered one-dimensional magnetic chains with a global invariance under a generic continuous group. Our methodology can be applied to any Lie-algebra valued spin Hamiltonian, in any representation. As examples, we focus on the physically relevant cases of SO(N) and Sp(N) magnetism, showing the existence of different randomness-dominated phases. These phases display emergent SU(N) symmetry at low energies and fall in two distinct classes, with meson-like or baryon-like characteristics. Our methodology is here explained in detail and helps to shed light on a general mechanism for symmetry emergence in disordered systems.Comment: 26 pages, 12 figure

Massive Black Hole Binary Systems in Hierarchical Scenario of Structure Formation

The hierarchical scenario of structure formation describes how objects like galaxies and galaxy clusters are formed by mergers of small objects. In this scenario, mergers of galaxies can lead to the formation of massive black hole (MBH) binary systems. On the other hand, the merger of two MBH could produce a gravitational wave signal detectable, in principle, by the Laser Interferometer Space Antenna (LISA). In the present work, we use the Press-Schechter formalism, and its extension, to describe the merger rate of haloes which contain massive black holes. Here, we do not study the gravitational wave emission of these systems. However, we present an initial study to determine the number of systems formed via mergers that could permit, in a future extension of this work, the calculation of the signature in gravitational waves of these systems.Comment: to match the published version in International Journal of Modern Physics

The prediction of liquid film journal bearing performance with a consideration of lubricant film reformation: part 2: experimental resuIts

Analyses and design data for plainjournal bearings rarely take into account the phenomenon of film reformation. The consideration of the re-establishment of the lubricantfilm after the cavitation region is difficult in a number of ways. The importance of allowingfor reformation is, however, being increasingly recognized. Tht.J is particularly true as regards the satisfactory predlction of lubricant ftowrate...and the thermal operating characteristics of a bearing. The authors have previously implemented a cavitation algorithm to enable the cavitation region in a plain journal bearing to be Iocated automatically and efficiently in a computer analysis. In Part I of the present paper theoretical results have been presentedfor the case of a plain bearing with a square-ended, axial groove located at the position of maximumfilm thickness. The second part of the paper gives detai/s of an experimental investigation designed to establish the validity of the analysis

UV-filter pollution: current concerns and future prospects.

UV-filters are widely used in cosmetics and personal care products to protect users' skin from redamage caused by ultraviolet (UV) radiation from the sun. Globally, an estimated 16,000 to 25,000 tonnes of products containing UV-filters were used in 2014 with modern consumption likely to be much higher. Beyond this use in cosmetics and personal care products, UV-filters are also widely used to provide UV-stability in industrial products such as paints and plastics. This review discusses the main routes by which UV-filters enter aquatic environments and summarises the conclusions of studies from the past 10 years that have investigated the effects of UV-filters on environmentally relevant species including corals, microalgae, fish, and marine mammals. Safety data regarding the potential impact of UV-filters on human health are also discussed. Finally, we explore the challenges surrounding UV-filter removal and research on more environmentally friendly alternatives to current UV-filters. [Abstract copyright: © 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies

Computing labs and Technology Classroom (ClTC) Initiative: A Model for Distributed Support

DePauw University is a small, liberal arts institution with 2200 undergraduate residential students and 222 faculty members, located in Greencastle, Indiana The challenges of supporting a campus with multiple and diverse facilities are further amplified by limited staff support resources. One of the strategies for addressing these challenges led to the formation of the Computing Labs and Technology Classrooms (CLTC) initiative. The CLTC recognizes and draws on the strengths of support specialists with a wide variety of professional training and experience, who regularly collaborate in the support and management of campus-wide labs and technology classrooms

FUSE Observations of Nebular O VI Emission from NGC 6543

NGC 6543 is one of the few planetary nebulae (PNe) whose X-ray emission has been shown to be extended and originate from hot interior gas. Using FUSE observations we have now detected nebular O VI emission from NGC 6543. Its central star, with an effective temperature of ~50,000 K, is too cool to photoionize O V, so the O VI ions must have been produced by thermal collisions at the interface between the hot interior gas and the cool nebular shell. We modeled the O VI emission incorporating thermal conduction, but find that simplistic assumptions for the AGB and fast wind mass loss rates overproduce X-ray emission and O VI emission. We have therefore adopted the pressure of the interior hot gas for the interface layer and find that expected O VI emission to be comparable to the observations.Comment: 4 pages, 4 figures, 1 table, using emulateapj.cls style. Accepted for publication in ApJ Letter