8,364 research outputs found
The beginnings of geography teaching and research in the University of Glasgow: the impact of J.W. Gregory
J.W. Gregory arrived in Glasgow from Melbourne in 1904 to take up the post of foundation Professor of Geology in the University of Glasgow. Soon after his arrival in Glasgow he began to push for the setting up of teaching in Geography in Glasgow, which came to pass in 1909 with the appointment of a Lecturer in Geography. This lecturer was based in the Department of Geology in the University's East Quad. Gregory's active promotion of Geography in the University was matched by his extensive writing in the area, in textbooks, journal articles and popular books. His prodigious output across a wide range of subject areas is variably accepted today, with much of his geomorphological work being judged as misguided to varying degrees. His 'social science' publications - in the areas of race, migration, colonisation and economic development of Africa and Australia - espouse a viewpoint that is unacceptable in the twenty-first century. Nonetheless, that viewpoint sits squarely within the social and economic traditions of Gregory's era, and he was clearly a key 'Establishment' figure in natural and social sciences research in the first half of the twentieth century. The establishment of Geography in the University of Glasgow remains enduring testimony of J.W. Gregory's energy, dedication and foresight
Coulomb interaction signatures in self-assembled lateral quantum dot molecules
We use photoluminescence spectroscopy to investigate the ground state of
single self-assembled InGaAs lateral quantum dot molecules. We apply a voltage
along the growth direction that allows us to control the total charge occupancy
of the quantum dot molecule. Using a combination of computational modeling and
experimental analysis, we assign the observed discrete spectral lines to
specific charge distributions. We explain the dynamic processes that lead to
these charge configurations through electrical injection and optical
generation. Our systemic analysis provides evidence of inter-dot tunneling of
electrons as predicted in previous theoretical work.Comment: 9 pages, 4 figure
Scalar Mesons a0(1450) and sigma(600) from Lattice QCD
We study the a0 and sigma mesons with the overlap fermion in the chiral
regime with the pion mass as low as 182 MeV in the quenched approximation.
After the eta'pi ghost states are separated, we find that the a0 mass with
q\bar{q} interpolation field to be almost independent of the quark mass in the
region below the strange quark mass. The chirally extrapolated results are
consistent with a0(1450) being the u\bar{d} meson and K0*(1430) being the
u\bar{s} meson with calculated masses at 1.42+_0.13 GeV and 1.41+_ 0.12 GeV
respectively. We also calculate the scalar mesonium with a tetraquark
interpolation field. In addition to the two pion scattering states, we find a
state at around 550 MeV. Through the study of volume dependence, we confirm
that this state is a one-particle state, in contrast to the two-pion scattering
states. This suggests that the observed state is a tetraquark mesonium which is
quite possibly the sigma(600) meson.Comment: 11 pages, 9 figures, accepted for publication in Phys. Rev.
Schwarzschild-De Sitter black holes in 4+1 dimensional bulk
We construct a static solution for 4+1 dimensional bulk such that the 3+1
dimensional world has a linear warp factor and describes the
Schwarzschild-dS_{4} black hole. For m=0 this four dimensional universe and
Friedmann Robertson Walker universe are related with an explicit coordinate
transformation. We emphasize that for linear warp factors the effect of bulk on
the brane world shows up as the dS_{4} background which is favored by the big
bang cosmology.Comment: 6 page
Mass Accretion onto T Tauri Stars
It is now accepted that accretion onto classical T Tauri stars is controlled
by the stellar magnetosphere, yet to date most accretion models have assumed
that their magnetic fields are dipolar. By considering a simple steady state
accretion model with both dipolar and complex magnetic fields we find a
correlation between mass accretion rate and stellar mass of the form , with our results consistent within observed
scatter. For any particular stellar mass there can be several orders of
magnitude difference in the mass accretion rate, with accretion filling factors
of a few percent. We demonstrate that the field geometry has a significant
effect in controlling the location and distribution of hot spots, formed on the
stellar surface from the high velocity impact of accreting material. We find
that hot spots are often at mid to low latitudes, in contrast to what is
expected for accretion to dipolar fields, and that particularly for higher mass
stars, the accretion flow is predominantly carried by open field lines.Comment: 17 pages, 10 figures, accepted for publication by MNRA
Nonsingular global string compactifications
We consider an exotic `compactification' of spacetime in which there are two
infinite extra dimensions, using a global string instead of a domain wall. By
having a negative cosmological constant we prove the existence of a nonsingular
static solution using a dynamical systems argument. A nonsingular solution also
exists in the absence of a cosmological constant with a time-dependent metric.
We compare and contrast this solution with the Randall-Sundrum universe and the
Cohen-Kaplan spacetime, and consider the options of using such a model as a
realistic resolution of the hierarchy problem.Comment: 8 pages revtex, 1 figure : References added and equation correcte
Ambiguous figures and the content of experience
Representationalism is the position that the phenomenal character of an experience is either identical with, or supervenes on, the content of that experience. Many representationalists hold that the relevant content of experience is nonconceptual. I propose a counterexample to this form of representationalism that arises from the phenomenon of Gestalt switching, which occurs when viewing ambiguous figures. First, I argue that one does not need to appeal to the conceptual content of experience or to judgements to account for Gestalt switching. I then argue that experiences of certain ambiguous figures are problematic because they have different phenomenal characters but that no difference in the nonconceptual content of these experiences can be identified. I consider three solutions to this problem that have been proposed by both philosophers and psychologists and conclude that none can account for all the ambiguous figures that pose the problem. I conclude that the onus is on representationalists to specify the relevant difference in content or to abandon their position
Singular responses of spin-incoherent Luttinger liquids
When a local potential changes abruptly in time, an electron gas shifts to a
new state which at long times is orthogonal to the one in the absence of the
local potential. This is known as Anderson's orthogonality catastrophe and it
is relevant for the so-called X-ray edge or Fermi edge singularity, and for
tunneling into an interacting one dimensional system of fermions. It often
happens that the finite frequency response of the photon absorption or the
tunneling density of states exhibits a singular behavior as a function of
frequency: where is a
threshold frequency and is an exponent characterizing the singular
response. In this paper singular responses of spin-incoherent Luttinger liquids
are reviewed. Such responses most often do not fall into the familiar form
above, but instead typically exhibit logarithmic corrections and display a much
higher universality in terms of the microscopic interactions in the theory.
Specific predictions are made, the current experimental situation is
summarized, and key outstanding theoretical issues related to spin-incoherent
Luttinger liquids are highlighted.Comment: 21 pages, 3 figures. Invited Topical Review Articl
Bayesian Analysis of the Polarization of Distant Radio Sources: Limits on Cosmological Birefringence
A recent study of the rotation of the plane of polarization of light from 160
cosmological sources claims to find significant evidence for cosmological
anisotropy. We point out methodological weaknesses of that study, and reanalyze
the same data using Bayesian methods that overcome these problems. We find that
the data always favor isotropic models for the distribution of observed
polarizations over counterparts that have a cosmological anisotropy of the type
advocated in the earlier study. Although anisotropic models are not completely
ruled out, the data put strong lower limits on the length scale (in
units of the Hubble length) associated with the anisotropy; the lower limits of
95% credible regions for lie between 0.43 and 0.62 in all anisotropic
models we studied, values several times larger than the best-fit value of
found in the earlier study. The length scale is not
constrained from above. The vast majority of sources in the data are at
distances closer than 0.4 Hubble lengths (corresponding to a redshift of
0.8); the results are thus consistent with there being no significant
anisotropy on the length scale probed by these data.Comment: 8 pages, 3 figures; submitted to Phys. Rev.
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