63 research outputs found
Colloform high-purity platinum from the placer deposit of Koura River (Gornaya Shoriya, Russia)
A microinclusion of colloform high-purity platinum in a grain of platinum-group minerals (PGM) from the alluvial gold-bearing placer deposit in the south of Western Siberia (Russia) was detected and characterized for the first time. It is different in composition, texture, and conditions of formation from high-purity platinum of other regions described in the literature. The main characteristics of investigated high-purity platinum are colloform-layered texture, admixture of Fe (0.37–0.78 wt%), and paragenesis of Cu-rich isoferroplatinum, hongshiite, and rhodarsenide. The PGM grain with high-purity platinum is multiphase and heterogeneous in texture. It is a product of intensive metasomatic transformation of Cu-rich isoferroplatinum (Pt3(Fe0.6Cu0.4)). The transformation was carried out in two stages: 1 – copper stage including three substages (Cu-rich isoferroplatinum, copper platinum and hongshiite); and 2 – arsenic (rhodarsenide). The formation of high-purity platinum was separated in time from the formation of isoferroplatinum and was carried out by precipitation from postmagmatic solutions
Experimental Reconstruction of Lomonosov's Discovery of Venus's Atmosphere with Antique Refractors During the 2012 Transit of Venus
In 1761, the Russian polymath Mikhail Vasilievich Lomonosov (1711-1765)
discovered the atmosphere of Venus during its transit over the Sun's disc. In
this paper we report on experimental reenactments of Lomonosov's discovery with
antique refractors during the transit of Venus June 5-6, 2012. We conclude that
Lomonosov's telescope was fully adequate to the task of detecting the arc of
light around Venus off the Sun's disc during ingress or egress if proper
experimental techniques as described by Lomonosov in his 1761 report are
employed.Comment: 14 pages, 9 figure
Quasi-normal frequencies: Key analytic results
The study of exact quasi-normal modes [QNMs], and their associated
quasi-normal frequencies [QNFs], has had a long and convoluted history -
replete with many rediscoveries of previously known results. In this article we
shall collect and survey a number of known analytic results, and develop
several new analytic results - specifically we shall provide several new QNF
results and estimates, in a form amenable for comparison with the extant
literature. Apart from their intrinsic interest, these exact and approximate
results serve as a backdrop and a consistency check on ongoing efforts to find
general model-independent estimates for QNFs, and general model-independent
bounds on transmission probabilities. Our calculations also provide yet another
physics application of the Lambert W function. These ideas have relevance to
fields as diverse as black hole physics, (where they are related to the damped
oscillations of astrophysical black holes, to greybody factors for the Hawking
radiation, and to more speculative state-counting models for the Bekenstein
entropy), to quantum field theory (where they are related to Casimir energies
in unbounded systems), through to condensed matter physics, (where one may
literally be interested in an electron tunelling through a physical barrier).Comment: V1: 29 pages; V2: Reformatted, 31 pages. Title changed to reflect
major additions and revisions. Now describes exact QNFs for the double-delta
potential in terms of the Lambert W function. V3: Minor edits for clarity.
Four references added. No physics changes. Still 31 page
An approach for the calculation of one-loop effective actions, vacuum energies, and spectral counting functions
In this paper, we provide an approach for the calculation of one-loop
effective actions, vacuum energies, and spectral counting functions and discuss
the application of this approach in some physical problems. Concretely, we
construct the equations for these three quantities; this allows us to achieve
them by directly solving equations. In order to construct the equations, we
introduce shifted local one-loop effective actions, shifted local vacuum
energies, and local spectral counting functions. We solve the equations of
one-loop effective actions, vacuum energies, and spectral counting functions
for free massive scalar fields in , scalar fields in
three-dimensional hyperbolic space (the Euclidean Anti-de Sitter space
), in (the geometry of the Euclidean BTZ black hole), and in
, and the Higgs model in a -dimensional finite interval.
Moreover, in the above cases, we also calculate the spectra from the counting
functions. Besides exact solutions, we give a general discussion on approximate
solutions and construct the general series expansion for one-loop effective
actions, vacuum energies, and spectral counting functions. In doing this, we
encounter divergences. In order to remove the divergences, renormalization
procedures are used. In this approach, these three physical quantities are
regarded as spectral functions in the spectral problem.Comment: 37 pages, no figure. This is an enlarged and improved version of the
paper published in JHE
Gauge symmetry and W-algebra in higher derivative systems
The problem of gauge symmetry in higher derivative Lagrangian systems is
discussed from a Hamiltonian point of view. The number of independent gauge
parameters is shown to be in general {\it{less}} than the number of independent
primary first class constraints, thereby distinguishing it from conventional
first order systems. Different models have been considered as illustrative
examples. In particular we show a direct connection between the gauge symmetry
and the W-algebra for the rigid relativistic particle.Comment: 1+22 pages, 1 figure, LaTeX, v2; title changed, considerably expanded
version with new results, to appear in JHE
Towards strange metallic holography
We initiate a holographic model building approach to `strange metallic'
phenomenology. Our model couples a neutral Lifshitz-invariant quantum critical
theory, dual to a bulk gravitational background, to a finite density of gapped
probe charge carriers, dually described by D-branes. In the physical regime of
temperature much lower than the charge density and gap, we exhibit anomalous
scalings of the temperature and frequency dependent conductivity. Choosing the
dynamical critical exponent appropriately we can match the non-Fermi liquid
scalings, such as linear resistivity, observed in strange metal regimes. As
part of our investigation we outline three distinct string theory realizations
of Lifshitz geometries: from F theory, from polarised branes, and from a
gravitating charged Fermi gas. We also identify general features of
renormalisation group flow in Lifshitz theories, such as the appearance of
relevant charge-charge interactions when . We outline a program to
extend this model building approach to other anomalous observables of interest
such as the Hall conductivity.Comment: 71 pages, 8 figure
Identification of alleles of carotenoid pathway genes important for zeaxanthin accumulation in potato tubers
We have investigated the genetics and molecular biology of orange flesh colour in potato (Solanum tuberosum L.). To this end the natural diversity in three genes of the carotenoid pathway was assessed by SNP analyses. Association analysis was performed between SNP haplotypes and flesh colour phenotypes in diploid and tetraploid potato genotypes. We observed that among eleven beta-carotene hydroxylase 2 (Chy2) alleles only one dominant allele has a major effect, changing white into yellow flesh colour. In contrast, none of the lycopene epsilon cyclase (Lcye) alleles seemed to have a large effect on flesh colour. Analysis of zeaxanthin epoxidase (Zep) alleles showed that all (diploid) genotypes with orange tuber flesh were homozygous for one specific Zep allele. This Zep allele showed a reduced level of expression. The complete genomic sequence of the recessive Zep allele, including the promoter, was determined, and compared with the sequence of other Zep alleles. The most striking difference was the presence of a non-LTR retrotransposon sequence in intron 1 of the recessive Zep allele, which was absent in all other Zep alleles investigated. We hypothesise that the presence of this large sequence in intron 1 caused the lower expression level, resulting in reduced Zep activity and accumulation of zeaxanthin. Only genotypes combining presence of the dominant Chy2 allele with homozygosity for the recessive Zep allele produced orange-fleshed tubers that accumulated large amounts of zeaxanthin
FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2
In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics
HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4
In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries
FCC Physics Opportunities: Future Circular Collider Conceptual Design Report Volume 1
We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synergy and complementarity of the different colliders, which will contribute to a uniquely coherent and ambitious research programme, providing an unmatchable combination of precision and sensitivity to new physics
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