5,110 research outputs found
Interference and complementarity for two-photon hybrid entangled states
In this work we generate two-photon hybrid entangled states (HES), where the
polarization of one photon is entangled with the transverse spatial degree of
freedom of the second photon. The photon pair is created by parametric
down-conversion in a polarization-entangled state. A birefringent double-slit
couples the polarization and spatial degrees of freedom of these photons and
finally, suitable spatial and polarization projections generate the HES. We
investigate some interesting aspects of the two-photon hybrid interference, and
present this study in the context of the complementarity relation that exists
between the visibilities of the one- and two-photon interference patterns.Comment: 10 pages, 4 figures. Accepted in Physical Review
Charged Dilaton Black Holes with a Cosmological Constant
The properties of static spherically symmetric black holes, which are either
electrically or magnetically charged, and which are coupled to the dilaton in
the presence of a cosmological constant, are considered. It is shown that such
solutions do not exist if the cosmological constant is positive (in arbitrary
spacetime dimension >= 4). However, asymptotically anti-de Sitter black hole
solutions with a single horizon do exist if the cosmological constant is
negative. These solutions are studied numerically in four dimensions and the
thermodynamic properties of the solutions are derived. The extreme solutions
are found to have zero entropy and infinite temperature for all non-zero values
of the dilaton coupling constant.Comment: 12 pages, epsf, phyzzx, 4 in-text figures incl. (minor typos fixed, 1
reference added
Sports mega-events – three sites of contemporary political contestation
This article discusses the contemporary politics of sports mega-events, involving the Olympic Games and Fédération Internationale de Football Association (FIFA) Men’s Football World Cup Finals as well as other lower ‘order’ sports megas, taking two main forms: the promotional and the protest. There is a politics in, and a politics of, sports mega-events. The former focuses on the internal politics of the organizing bodies, such as the International Olympic Committee and FIFA. This form of politics has been written about elsewhere, and hence, there is no detailed discussion in this article about it. Instead this article offers a brief discussion of the range and number of sports mega-events since 2000, an assessment of the contemporary politics of sports mega-events, a focus on three main sites of political contestation – rights, legacy and labour, and finally, it offers conclusions about research into the politics of sports mega-events
A Radial Velocity Study of CTCV J1300-3052
We present time-resolved spectroscopy of the eclipsing, short period
cataclysmic variable CTCV J1300-3052. Using absorption features from the
secondary star, we determine the radial velocity semi-amplitude of the
secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity
to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo
techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf
primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These
parameters are found to be in excellent agreement with previous mass
determinations found via photometric fitting techniques, supporting the
accuracy and validity of photometric mass determinations in short period CVs.Comment: Accepted for publication in MNRAS (24th January 2012). 10 pages, 9
figures (black and white
HST and ground-based eclipse observations of V2051 Ophiuchi: Binary parameters
We report on high-speed eclipse photometry of the dwarf nova V2051 Oph while
it was in a low brightness state, at B ~ 16.2 mag. In comparison to the average
IUE spectra, the ultraviolet continuum and emission lines appear reduced by
factors of, respectively, ~4 and ~5. Flickering activity is mostly suppressed
and the lightcurve shows the eclipse of a compact white dwarf at disc centre
which contributes ~60 per cent of the total light at 3900--4300 A. We use
measurements of contact phases in the eclipse lightcurve to derive the binary
geometry and to estimate masses and relevant dimensions. We find a mass ratio
of q= 0.19+/-0.03 and an inclination of i= 83+/-2 degrees. The masses of the
component stars are M_1 = 0.78+/-0.06 M_dot and M_2 = 0.15+/-0.03 M_dot. Our
photometric model predicts K_1 = 83+/-12 km/s and K_2= 435+/-11 km/s. The
predicted value of K_1 is in accordance with the velocity amplitude obtained
from the emission lines after a correction for asymmetric line emission in the
disc is made (Watts et al. 1986). The secondary of V2051 Oph is significantly
more massive than the secondaries of the other ultra-short period dwarf novae.
V2051 Oph is probably a relatively young system, whose secondary star had not
enough time to evolve out of thermal equilibrium.Comment: 16 pages, 7 postscript figures, coded using MNRAS latex style. To
appear in Monthly Notices of the Royal Astronomical Society. Revised version
with changes in section 4.3. For related papers and files see
ftp://fsc01.fsc.ufsc.br/pub/bap and http://www.fsc.ufsc.br/~astr
On the logical structure of Bell theorems without inequalities
Bell theorems show how to experimentally falsify local realism. Conclusive
falsification is highly desirable as it would provide support for the most
profoundly counterintuitive feature of quantum theory - nonlocality. Despite
the preponderance of evidence for quantum mechanics, practical limits on
detector efficiency and the difficulty of coordinating space-like separated
measurements have provided loopholes for a classical worldview; these loopholes
have never been simultaneously closed. A number of new experiments have
recently been proposed to close both loopholes at once. We show some of these
novel designs fail in the most basic way, by not ruling out local hidden
variable models, and we provide an explicit classical model to demonstrate
this. They share a common flaw, which reveals a basic misunderstanding of how
nonlocality proofs work. Given the time and resources now being devoted to such
experiments, theoretical clarity is essential. Our explanation is presented in
terms of simple logic and should serve to correct misconceptions and avoid
future mistakes. We also show a nonlocality proof involving four participants
which has interesting theoretical properties.Comment: 8 pages, text clarified, explicit LHV model provided for flawed
nonlocality tes
A search for starlight reflected from HD 75289 b
We have used a doppler tomographic analysis to conduct a deep search for the
starlight reflected from the planetary companion to HD 75289. In 4 nights on
VLT2/UVES in January 2003, we obtained 684 high resolution echelle spectra with
a total integration time of 26 hours. We establish an upper limit on the
planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the
most probable orbital inclination i ~ 60 degrees, assuming a grey albedo, a
Venus-like phase function and a planetary radius R_p = 1.6 R_Jup. We are able
to rule out some combinations of the predicted planetary radius and atmospheric
albedo models with high, reflective cloud decks.Comment: 5 pages, 5 figures, MNRAS accepted 12 Oct 200
Short-term effects of deep ploughing on soil C stocks following renewal of a dairy pasture in New Zealand
In New Zealand’s high producing permanent pastures the topsoil constitutes a large reservoir of soil organic carbon (SOC), which shows a marked stratification with depth. As consequence, sub-surface layers can contain 10 times less carbon than the surface soil. In permanent pastures with high carbon inputs, the formation and decomposition of these surface SOC stocks are often at equilibrium and C storage shows little change over time. Pastoral based dairy systems utilising ryegrass plus clover cultivars require renewal every 7-10 years to avoid reversion to less productive grasses. This may involve spring cultivation (either no-till, shallow till or full cultivation), summer forage cropping and autumn re-grassing. It has been hypothesised that SOC stocks can be increased by inverting the soil profile at pasture renewal through infrequent (once in 25-30 years) deep mouldboard ploughing (up to 30 cm depth). Increased C sequestration occurs when the new grass quickly rebuilds SOC stocks in the new topsoil (exposed low C sub-soil) at a rate faster than the decomposition of SOC in the rich former topsoil transferred to depth (now below 15 cm). However, benefits form accelerated C storage may be offset if crop and pasture production is adversely affected by the ploughing event (e.g., as result of compaction or excessive drainage). Hence, the aim of this work was to assess the short-term effects of infrequent inversion tillage of long-term New Zealand pastoral-based dairy soils under summer crop management and autumn re-grassing. An imperfectly drained Typic Fragiaqualf under dairy grazing was deep ploughed (approx. 25 cm) and re-sown with turnip in October 2016; other treatments included were shallow (< 10 cm) cultivation and no-till. The site was core sampled (0-40 cm) before cultivation and after 5 months of turnip growth to assess changes in SOC. Plant growth, herbage quality, and nutrient leaching were monitored during the 5-month period; root growth was assessed at the end of the crop rotation. Full cultivation transferred SOC below 10 cm depth, as expected. Soil bulk density decreased whereas root mass increased (10-20 cm depth; P < 0.05) under deep cultivation only. Besides, losses of mineral N were attenuated under deep tillage, resulting in a relative increase in crop yield. The potential for infrequent inversion tillage increasing soil C sequestration as a greenhouse gas (GHG) mitigation tool is currently being tested at other sites in New Zealand
Continuous Self-Similarity and -Duality
We study the spherically symmetric collapse of the axion/dilaton system
coupled to gravity. We show numerically that the critical solution at the
threshold of black hole formation is continuously self-similar. Numerical and
analytical arguments both demonstrate that the mass scaling away from
criticality has a critical exponent of .Comment: 17 pages, harvmac, six figures uuencoded in separate fil
Plantain (\u3cem\u3ePlantago lanceolata\u3c/em\u3e L.) Growth Islimited Under Waterlogging
Plantain (Plantago lanceolata L.; PL) is becoming an increasingly important component of New Zealand dairy pastures because of its ability to reduce nitrogen losses to the environment. However, widespread suggestions of its poor persistence, have led to industry concern over its suitability for dairy systems. Anecdotal evidence suggests that PL does not cope well in waterlogged soil, yet there is little scientific literature relevant to this issue. Thus, the aim of this study was to investigate the impact of waterlogging stress on PL growth and survival. In a glasshouse, the performance of PL under waterlogging was evaluated against perennial ryegrass (Lolium perenne L.; PRG), the predominant plant species in New Zealand dairy pastures. Three watering regimes were applied to PL and PRG plants in plastic pots: control (optimal watering), wet (soil at field capacity), and waterlogged (water table 5cm below the soil surface) for 39 days, before 27 days of recovery under control watering. Plant dry mass (DM) harvests were made on days 22, 39 and 66. The leaf DM of PL was reduced by the waterlogging treatment by 37% and 38% respectively during the treatment and recovery periods, in comparison with the control. In contrast, the leaf DM of PRG plants was only reduced by 18% and 3% by the waterlogging treatment during the treatment and recovery periods respectively, and so PRG produced 28% and 45% more leaf DM under waterlogging than PL, during the treatment and recovery periods, respectively. The root DM of PRG was 33% higher under waterlogging in comparison with the control at day 39, while PL root DM was not significantly affected by water treatment. Whilst PL growth appears to be sensitive to waterlogging stress, the survival of PL under waterlogged conditions suggests that it possesses some waterlogging tolerance strategies. PRG exhibited an enhanced ability for coping under, and recovering from waterlogging stress, which may have been associated with the maintenance of root growth under waterlogging. These findings suggest that PL growth may be somewhat limited in periodically waterlogged pastures, and the enhanced ability of PRG to cope with waterlogging stress, could provide it with a competitive advantage over PL under such conditions, should they coexist in a mixed sward
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