Giant electrocaloric effect around Tc_c

We use molecular dynamics with a first-principles-based shell model potential to study the electrocaloric effect (ECE) in lithium niobate, LiNbO$_3$, and find a giant electrocaloric effect along a line passing through the ferroelectric transition. With applied electric field, a line of maximum ECE passes through the zero field ferroelectric transition, continuing along a Widom line at high temperatures with increasing field, and along the instability that leads to homogeneous ferroelectric switching below $T_c$ with an applied field antiparallel to the spontaneous polarization. This line is defined as the minimum in the inverse capacitance under applied electric field. We investigate the effects of pressure, temperature and applied electric field on the ECE. The behavior we observe in LiNbO$_3$ should generally apply to ferroelectrics; we therefore suggest that the operating temperature for refrigeration and energy scavenging applications should be above the ferroelectric transition region to obtain large electrocaloric response. We find a relationship among $T_c$, the Widom line and homogeneous switching that should be universal among ferroelectrics, relaxors, multiferroics, and the same behavior should be found under applied magnetic fields in ferromagnets.Comment: 5 page

Disorder in order: Localization without randomness in a cold-atom system

We present a mapping between the Edwards model of disorder describing the motion of a single particle subject to randomly-positioned static scatterers and the Bose polaron problem of a light quantum impurity interacting with a Bose-Einstein condensate (BEC) of heavy atoms. The mapping offers an experimental setting to investigate the physics of Anderson localization where, by exploiting the quantum nature of the BEC, the time evolution of the quantum impurity emulates the disorder-averaged dynamics of the Edwards model. Valid in any space dimension, the mapping can be extended to include interacting particles, arbitrary disorder or confinement, and can be generalized to study many-body localization. Moreover, the corresponding exactly-solvable disorder model offers means to benchmark variational approaches used to study polaron physics. Here, we illustrate the mapping by focusing on the case of an impurity interacting with a one-dimensional BEC through a contact interaction. While a simple wave function based on the expansion in the number of bath excitations misses the localization physics entirely, a coherent state Ansatz combined with a canonical transformation captures the physics of disorder and Anderson localization.Comment: 10 pages, 4 figures. Definitive versio

Time evolution of the Partridge-Barton Model

The time evolution of the Partridge-Barton model in the presence of the pleiotropic constraint and deleterious somatic mutations is exactly solved for arbitrary fecundity in the context of a matricial formalism. Analytical expressions for the time dependence of the mean survival probabilities are derived. Using the fact that the asymptotic behavior for large time $t$ is controlled by the largest matrix eigenvalue, we obtain the steady state values for the mean survival probabilities and the Malthusian growth exponent. The mean age of the population exhibits a $t^{-1}$ power law decayment. Some Monte Carlo simulations were also performed and they corroborated our theoretical results.Comment: 10 pages, Latex, 1 postscript figure, published in Phys. Rev. E 61, 5664 (2000

The limits of process: On (re)reading Henri Bergson

This article offers a reading of the work of Henri Bergson as it pertains to organizations through the lens of ideas drawn from critical realism. It suggests an alternative to interpretations based on a stark division between process and realist perspectives. Much of the existing literature presents a rather partial view of Bergson’s work. A review suggests some interesting parallels with themes in critical realism, notably the emergence of mind. Critical realism has a focus on process at its heart, but is also concerned with how the products of such processes become stabilized and form the conditions for action. This suggests that attention might usefully be paid to the relationship between organizational action and the sedimented practices grouped under the heading of ‘routines’. More attention to Bergson’s account of the relationship between instinct, intuition and intelligence provides a link to the social character of thought, something which can be mapped on to Archer’s work on reflexivity and the ‘internal conversation’. This suggests that our analyses need to pay attention to both memory and history, to building and dwelling, rather than the one-sided focus found in some process theory accounts

Functional-renormalization-group approach to strongly coupled Bose-Fermi mixtures in two dimensions

We study theoretically the phase diagram of strongly coupled two-dimensional Bose-Fermi mixtures interacting with attractive short-range potentials as a function of the particle densities. We focus on the limit where the size of the bound state between a boson and a fermion is small compared to the average interboson separation and develop a functional-renormalization-group approach that accounts for the bound-state physics arising from the extended Fr\"{o}hlich Hamiltonian. By including three-body correlations we are able to reproduce the polaron-to-molecule transition in two-dimensional Fermi gases in the extreme limit of vanishing boson density. We predict frequency- and momentum-resolved spectral functions and study the impact of three-body correlations on quasiparticle properties. At finite boson density, we find that when the bound-state energy exceeds the Fermi energy by a critical value, the fermions and bosons can form a fermionic composite with a well-defined Fermi surface. These composites constitute a Fermi sea of dressed Feshbach molecules in the case of ultracold atoms while in the case of atomically thin semiconductors a trion liquid emerges. As the boson density is increased further, the effective energy gap of the composites decreases, leading to a transition into a strongly correlated phase where polarons are hybridized with molecular degrees of freedom. We highlight the universal connection between two-dimensional semiconductors and ultracold atoms and we discuss perspectives for further exploring the rich structure of strongly coupled Bose-Fermi mixtures in these complementary systems.Comment: 28 pages, 12 figure

The diffuse X-ray background spectrum from 3 to 50keV

The spectrum of the extragalactic diffuse X-ray background was measured with the GSFC cosmic X-ray experiment on HEAO-1 for regions of the sky away from known point sources and more than 20 deg from the galactic plane. A total exposure of 80 sq m-sec-sr is available at present. Free-free emission from an optically thin plasma of 40 plus or minus 5 keV provides an excellent description of the observed spectrum from 3 to 50 keV. This spectral shape is confirmed by measurements from 5 separate layers of three independent detectors. With an estimated absolute precision of about 10 percent, the intensity of the emission at 10 keV is 3.2 keV/keV-sq cm-sec-sr, a value consistent with the average of previously reported spectra. No other spectral features, such as iron line emission, are evident. This spectrum is not typical of known extragalactic objects. A uniform hot intergalactic medium of approximately 36 percent of the closure density of the universe would produce such a flux, although non-uniform models indicating less total matter are probably more realistic

Lokasi Penanaman Bawang Merah Lokal Samosir Berdasarkan Ketinggian Tempat Di Daerah Tangkapan Air Danau Toba

Penelitian ini bertujuan untuk menentukan lokasi penanaman bawang merah lokal Samosir berdasarkan ketinggian tempat di Daerah Tangkapan Air Danau Toba. Penelitian ini dilaksanakan di sentra kawasan penanaman bawang merah di daerah sekitaran Danau Toba dengan ketinggian tempat 900 – 2000 meter diatas permukaan laut. Penelitian ini dilaksanakan dengan metode survey yang meliputi studi literatur, penyusunan kuisioner, survey lapangan dan pengolahan data hasil survey lapangan. Hasil penelitian menunjukkan bahwa ketinggian tempat dan produksi bawang merah lokal Samosir berkorelasi negatif, artinya semakin tinggi ketinggian tempat maka produksi akan menurun dengan nilai r = 0.51. Ketinggian tempat yang terbaik untuk budidaya bawang merah lokal Samosir di DTA Danau Toba adalah ketinggian 900 – 1000 m dpl

Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity

We investigate some aspects of anomaly cancellation realized by the subtraction of an anomaly pole, stressing on some of its properties in superspace. In a local formulation these subtractions can be described in terms of a physical scalar, an axion and related ghosts. They appear to be necessary for the unitarization of the theory in the ultraviolet, but they may generate an infrared instability of the corresponding effective action, signalled by ghost condensation. In particular the subtraction of the superanomaly multiplet by a pole in superspace is of dubious significance, due to the different nature of the chiral and conformal anomalies. In turn, this may set more stringent constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum Gravity

Consequences of wall stiffness for a beta-soft potential

Modifications of the infinite square well E(5) and X(5) descriptions of transitional nuclear structure are considered. The eigenproblem for a potential with linear sloped walls is solved. The consequences of the introduction of sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.

Fertility and well-being in the italian regions

We analyse the association between fertility rates and well-being in the Italian regions in the period 2012-2017. Well-being is measured by the indicators of Equitable and Sustainable Well-being (BES), collected by ISTAT since 2013 with the aim of evaluating the economic, social and environmental development of the society through measurement of citizens’ life quality. We expect that the regions performing better in terms of well-being conditions are also those with the highest levels of fertility. Both graphical and panel data regression analyses support our main hypothesis, but also reveal that in different clusters of regions the intensity and direction of the relationship significantly change. Our results also stress the need of taking the different domains of well-being into account while explaining reproductive behaviour of resident population at territorial level