15,788 research outputs found
Some comments on embedding inflation in the AdS/CFT correspondence
The anti-de Sitter space/conformal field theory correspondence (AdS/CFT) can
potentially provide a complete formulation of string theory on a landscape of
stable and metastable vacua that naturally give rise to eternal inflation. As a
model for this process, we consider bubble solutions with de Sitter interiors,
obtained by patching together dS and Schwarzschild-AdS solutions along a bubble
wall. For an interesting subclass of these solutions the bubble wall reaches
spacelike infinity in the black hole interior. Including the effects of
perturbations leads to a null singularity emanating from this point. Such
solutions are interpreted as states in a single CFT, and are shown to be
compatible with holographic entropy bounds. The construction suggests de Sitter
entropy be interpreted as the total number of degrees of freedom in effective
field theory, with a novel adaptive stepsize cutoff.Comment: 15 pages, 4 figures, revtex
Causal closure principles and emergentism
Causal closure arguments against interactionist dualism are currently popular amongst physicalists. Such an argument appeals to some principles of the causal closure of the physical, together with certain other premises, to conclude that at least some mental events are identical with physical events. However, it is crucial to the success of any such argument that the physical causal closure principle to which it appeals is neither too strong nor too weak by certain standards. In this paper, it is argued that various forms of naturalistic dualism, of an emergentist character, are consistent with the strongest physical causal closure principles that can plausibly be advocated
Solar cell radiation response near the interface of different atomic number materials
The response of cobalt 60 irradiated N/P silicon solar cells was measured as a function of the atomic number of the medium adjacent to the cell and the direction of the gamma ray beam. The interpositioning of various thicknesses of aluminum between the adjacent material and the cell had the effect of moving the cell to various locations in an approximate monatomic numbered medium. Using this technique the solar cell response was determined at various distances from the interface for gold and beryllium. The results were compared with predictions based upon ionization chamber measurements of dose perturbations in aluminum and found to agree within five percent. Ionization chamber data was then used to estimate the influence of various base contact materials
Identity, individuality, and unity
Locke notoriously included number amongst the primary qualities of bodies and was roundly criticized for doing so by Berkeley. Frege echoed some of Berkeley's criticisms in attacking the idea that âNumber is a property of external thingsâ, while defending his own view that number is a property of concepts. In the present paper, Locke's view is defended against the objections of Berkeley and Frege, and Frege's alternative view of number is criticized. More precisely, it is argued that numbers are assignable to pluralities of individuals. However, it is also argued that Locke went too far in asserting that âNumber applies itself to ... everything that either doth exist, or can be imaginedâ
Resolving the black hole information paradox
The recent progress in string theory strongly suggests that formation and
evaporation of black holes is a unitary process. This fact makes it imperative
that we find a flaw in the semiclassical reasoning that implies a loss of
information. We propose a new criterion that limits the domain of classical
gravity: the hypersurfaces of a foliation cannot be stretched too much. This
conjectured criterion may have important consequences for the early Universe.Comment: harvmac, 11 pages (1 figure) (This essay received an ``honorable
mention'' in the Annual Essay Competition of the Gravity Research Foundation
for the year 2000.
Security Attributes Based Digital Rights Management
Most real-life systems delegate responsibilities to different authorities. We apply this model to a digital rights management system, to achieve flexible security. In our model a hierarchy of authorities issues certificates that are linked by cryptographic means. This linkage establishes a chain of control, identity-attribute-rights, and allows flexible rights control over content. Typical security objectives, such as identification, authentication, authorization and access control can be realised. Content keys are personalised to detect illegal super distribution. We describe a working prototype, which we develop using standard techniques, such as standard certificates, XML and Java. We present experimental results to evaluate the scalability of the system. A formal analysis demonstrates that our design is able to detect a form of illegal super distribution
RPNet: an End-to-End Network for Relative Camera Pose Estimation
This paper addresses the task of relative camera pose estimation from raw
image pixels, by means of deep neural networks. The proposed RPNet network
takes pairs of images as input and directly infers the relative poses, without
the need of camera intrinsic/extrinsic. While state-of-the-art systems based on
SIFT + RANSAC, are able to recover the translation vector only up to scale,
RPNet is trained to produce the full translation vector, in an end-to-end way.
Experimental results on the Cambridge Landmark dataset show very promising
results regarding the recovery of the full translation vector. They also show
that RPNet produces more accurate and more stable results than traditional
approaches, especially for hard images (repetitive textures, textureless
images, etc). To the best of our knowledge, RPNet is the first attempt to
recover full translation vectors in relative pose estimation
Re-identification of c. 15 700 cal yr BP tephra bed at Kaipo Bog, eastern North Island: implications for dispersal of Rotorua and Puketarata tephra beds.
A 10 mm thick, c. 15 700 calendar yr BP (c. 13 100 14C yr BP) rhyolitic tephra bed in the well-studied montane Kaipo Bog sequence of eastern North Island was previously correlated with Maroa-derived Puketarata Tephra. We revise this correlation to Okataina-derived Rotorua Tephra based on new compositional data from biotite phenocrysts and glass. The new correlation limits the known dispersal of Puketarata Tephra (sensu stricto, c. 16 800 cal yr BP) and eliminates requirements to either reassess its age or to invoke dual Puketarata eruptive events. Our data show that Rotorua Tephra comprises two glass-shard types: an early-erupted low-K2O type that was dispersed mostly to the northwest, and a high-K2O type dispersed mostly to the south and southeast, contemporary with late-stage lava extrusion. Late-stage Rotorua eruptives contain biotite that is enriched in FeO compared with biotite from Puketarata pyroclastics. The occurrence of Rotorua Tephra in Kaipo Bog (100 km from the source) substantially extends its known distribution to the southeast. Our analyses demonstrate that unrecognised syn-eruption compositional and dispersal changes can cause errors in fingerprinting tephra deposits. However, the compositional complexity, once recognised, provides additional fingerprinting criteria, and also documents magmatic and dispersal processes
A study of blood contamination of Siqveland matrix bands
AIMS To use a sensitive forensic test to measure blood contamination of used Siqveland matrix bands following routine cleaning and sterilisation procedures in general dental practice. MATERIALS AND METHODS: Sixteen general dental practices in the West of Scotland participated. Details of instrument cleaning procedures were recorded for each practice. A total of 133 Siqveland matrix bands were recovered following cleaning and sterilisation and were examined for residual blood contamination by the Kastle-Meyer test, a well-recognised forensic technique. RESULTS: Ultrasonic baths were used for the cleaning of 62 (47%) bands and retainers and the remainder (53%) were hand scrubbed prior to autoclaving. Overall, 21% of the matrix bands and 19% of the retainers gave a positive Kastle-Meyer test, indicative of residual blood contamination, following cleaning and sterilisation. In relation to cleaning method, 34% of hand-scrubbed bands and 32% of hand-scrubbed retainers were positive for residual blood by the Kastle-Meyer test compared with 6% and 3% respectively of ultrasonically cleaned bands and retainers (P less than 0.001). CONCLUSIONS: If Siqveland matrix bands are re-processed in the assembled state, then adequate pre-sterilisation cleaning cannot be achieved reliably. Ultrasonic baths are significantly more effective than hand cleaning for these items of equipment
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