33,079 research outputs found
MEVTV study: Early tectonic evolution of Mars: Crustal dichotomy to Valles Marineris
Several fundamental problems were addressed in the early impact, tectonic, and volcanic evolution of the martian lithosphere: (1) origin and evolution of the fundamental crustal dichotomy, including development of the highland/lowland transition zone; (2) growth and evolution of the Valles Marineris; and (3) nature and role of major resurfacing events in early martian history. The results in these areas are briefly summarized
The Durham Statement Two Years Later: Open Access in the Law School Journal Environment
The Durham Statement on Open Access to Legal Scholarship, drafted by a group of academic law library directors, was promulgated in February 2009. It calls for two things: (1) open access publication of law schoolâpublished journals; and (2) an end to print publication of law journals, coupled with a commitment to keeping the electronic versions available in âstable, open, digital formats.â The two years since the Statement was issued have seen increased publication of law journals in openly available electronic formats, but little movement toward all-electronic publication. This article discusses the issues raised by the Durham Statement, the current state of law journal publishing, and directions forward
Mass-symmetry breaking in three-body ions
The ground-state energy of three-body ions evolves when the
like-charge constituents are given different masses. The comparison of
with the average of and
reveals a competition between the symmetric term and the
antisymmetric one. The former dominates in the Born--Oppenheimer regime such as
the (p,t,e) case, while the latter wins for H-like systems with two
negative light particles surrounding a heavy nucleus. A comparison is also made
with the case of baryons in simple quark models with flavour independence.Comment: 4 pages, 3 figure
Hydrodynamic theory of quantum fluctuating superconductivity
A hydrodynamic theory of transport in quantum mechanically phase-disordered
superconductors is possible when supercurrent relaxation can be treated as a
slow process. We obtain general results for the frequency-dependent
conductivity of such a regime. With time-reversal invariance, the conductivity
is characterized by a Drude-like peak, with width given by the supercurrent
relaxation rate. Using the memory matrix formalism, we obtain a formula for
this width (and hence also the dc resistivity) when the supercurrent is relaxed
by short range Coulomb interactions. This leads to a new -- effective field
theoretic and fully quantum -- derivation of a classic result on flux flow
resistance. With strong breaking of time-reversal invariance, the optical
conductivity exhibits what we call a `hydrodynamic supercyclotron' resonance.
We obtain the frequency and decay rate of this resonance for the case of
supercurrent relaxation due to an emergent Chern-Simons gauge field. The
supercurrent decay rate in this `topologically ordered superfluid vortex
liquid' is determined by the conductivities of the normal component of the
liquid. Our work gives a controlled framework for low temperature metallic
phases arising from phase-disordered superconductivity.Comment: 1 + 44 pages. 2 figures. v2 discussion improved in places. v3 sign
errors fixed in section
Asymptotics of surface-plasmon redshift saturation at sub-nanometric separations
Many promising nanophotonics endeavours hinge upon the unique plasmonic
properties of nanometallic structures with narrow non-metallic gaps, which
support super-concentrated bonding modes that singularly redshift with
decreasing separations. In this letter, we present a descriptive physical
picture, complemented by elementary asymptotic formulae, of a nonlocal
mechanism for plasmon-redshift saturation at subnanometric gap widths. Thus, by
considering the electron-charge and field distributions in the close vicinity
of the metal-vacuum interface, we show that nonlocality is asymptotically
manifested as an effective potential discontinuity. For bonding modes in the
near-contact limit, the latter discontinuity is shown to be effectively
equivalent to a widening of the gap. As a consequence, the resonance-frequency
near-contact asymptotics are a renormalisation of the corresponding local ones.
Specifically, the renormalisation furnishes an asymptotic plasmon-frequency
lower bound that scales with the -power of the Fermi wavelength. We
demonstrate these remarkable features in the prototypical cases of nanowire and
nanosphere dimers, showing agreement between our elementary expressions and
previously reported numerical computations
Surface-plasmon resonances of arbitrarily shaped nanometallic structures in the small-screening-length limit
According to the hydrodynamic Drude model, surface-plasmon resonances of
metallic nanostructures blueshift owing to the nonlocal response of the metal's
electron gas. The screening length characterising the nonlocal effect is often
small relative to the overall dimensions of the metallic structure, which
enables us to derive a coarse-grained nonlocal description using matched
asymptotic expansions; a perturbation theory for the blueshifts of arbitrary
shaped nanometallic structures is then developed. The effect of nonlocality is
not always a perturbation and we present a detailed analysis of the "bonding"
modes of a dimer of nearly touching nanowires where the leading-order
eigenfrequencies and eigenmode distributions are shown to be a renormalisation
of those predicted assuming a local metal permittivity
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