6,234 research outputs found
Abandonment of land and the Scottish Coal case : was it Unprecedented?
The support of the Carnegie Trust for the Universities of Scotland in the provision of a research incentive grant that contributed to this note is gratefully acknowledged.Peer reviewedPostprin
Bose Hubbard model in the presence of Ohmic dissipation
We study the zero temperature mean-field phase diagram of the Bose-Hubbard
model in the presence of local coupling between the bosons and an external
bath. We consider a coupling that conserves the on-site occupation number,
preserving the robustness of the Mott and superfluid phases. We show that the
coupling to the bath renormalizes the chemical potential and the interaction
between the bosons and reduces the size of the superfluid regions between the
insulating lobes. For strong enough coupling, a finite value of hopping is
required to obtain superfluidity around the degeneracy points where Mott phases
with different occupation numbers coexist. We discuss the role that such a bath
coupling may play in experiments that probe the formation of the
insulator-superfluid shell structure in systems of trapped atoms.Comment: 5 pages, 2 figures. Error found in v1, now corrected, leads to
qualitative changes in result
Schwinger-Keldysh approach to out of equilibrium dynamics of the Bose Hubbard model with time varying hopping
We study the real time dynamics of the Bose Hubbard model in the presence of
time-dependent hopping allowing for a finite temperature initial state. We use
the Schwinger-Keldysh technique to find the real-time strong coupling action
for the problem at both zero and finite temperature. This action allows for the
description of both the superfluid and Mott insulating phases. We use this
action to obtain dynamical equations for the superfluid order parameter as
hopping is tuned in real time so that the system crosses the superfluid phase
boundary. We find that under a quench in the hopping, the system generically
enters a metastable state in which the superfluid order parameter has an
oscillatory time dependence with a finite magnitude, but disappears when
averaged over a period. We relate our results to recent cold atom experiments.Comment: 22 pages, 7 figure
First evidence for interpersonal violence in Ukraine's Trypillian farming culture : Individual 3 from Verteba Cave, Bilche Zolote
This paper presents the initial stages of an interdisciplinary study of human skeletal remains interred at Verteba Cave, western Ukraine. This site has been described previously as a “ritual site of the Trypillian culture complex” by Nikitin et al. in Comprehensive site chronology and ancient mitochondrial DNA analysis from Verteba Cave – a Trypillian culture site of Eneolithic Ukraine, Interdisciplinaria Archaeologica: Natural Sciences in Archaeology 1, 9–18., and the material considered here is one of seven crania recovered during excavations at Verteba between 2008 and 2010. Palaeopathological analysis of the individual considered here indicates that this is a young adult female with evidence for peri-mortem injury, cranial surgery and into early stage Trypillia culture inter-personal interactions and burial ritual in this region of Ukraine. Paper published in Proceedings of the British Association for Biological Anthropology and Osteoarchaeology 13th and 14th Annual Conferences in Edinburgh (2nd-4th September 2011) and Bournemouth (14th–16th September 2012)
Mitochondrial DNA analysis of eneolithic trypillians from Ukraine reveals neolithic farming genetic roots
The agricultural revolution in Eastern Europe began in the Eneolithic with the Cucuteni-Trypillia culture complex. In Ukraine, the Trypillian culture (TC) existed for over two millennia (ca. 5,400–2,700 BCE) and left a wealth of artifacts. Yet, their burial rituals remain a mystery and to date almost nothing is known about the genetic composition of the TC population. One of the very few TC sites where human remains can be found is a cave called Verteba in western Ukraine. This report presents four partial and four complete mitochondrial genomes from nine TC individuals uncovered in the cave. The results of this analysis, combined with the data from previous reports, indicate that the Trypillian population at Verteba carried, for the most part, a typical Neolithic farmer package of mitochondrial DNA (mtDNA) lineages traced to Anatolian farmers and Neolithic farming groups of central Europe. At the same time, the find of two specimens belonging to haplogroup U8b1 at Verteba can be viewed as a connection of TC with the Upper Paleolithic European populations. At the level of mtDNA haplogroup frequencies, the TC population from Verteba demonstrates a close genetic relationship with population groups of the Funnel Beaker/ Trichterbecker cultural complex from central and northern Europe (ca. 3,950–2,500 BCE)
Lattice dynamics of incommensurate composite Rb-IV and a realization of the monatomic linear chain model
Longitudinal-acoustic (LA) phonons have been studied by inelastic x-ray scattering in the high-pressure incommensurate host-guest system Rb-IV in the pressure range of 16.3 to 18.4 GPa. Two LA-like phonon branches are observed along the direction of the incommensurate wave vector, which are attributed to separate lattice vibrations in the host and guest subsystems. The derived sound velocities for the host and the guest, nu(h) and nu(g), respectively, are similar in magnitude [nu(h)=nu(g)=3840(100) m/s at 18 GPa], but our results indicate rather different pressure dependences of dv(h)/dP=140(60) m/s GPa(-1) and d nu(g)/dP=280(80) m/s GPa(-1). The observations for the one-dimensional Rb guest chains are reproduced quantitatively on the basis of the monatomic linear chain model and the measured compressibility of the chains.</p
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