Deceleration without dark matter

In homogeneous isotropic cosmological models the angular size theta of a standard measuring rod changes with redshift z in a manner that depends upon the parameters of the model. It has been argued that as a population ultracompact (milliarcsecond) radio sources measured by very long-baseline interferometry (VLBI) do not evolve with cosmic epoch, and thus comprise a set of standard objects, at least in a statistical sense. Here we examine the angular-size/redshift relation for 256 ultracompact sources with z in the range 0.5 to 3.8 for cosmological models with two degrees of freedom (Omega_0 and Lambda_0). The canonical inflationary cold dark matter model(Omega_0=1, Lambda_0=0) appears to be ruled out by the observed relationship, whereas low-density models with a cosmological constant of either sign are favoured.Comment: Although published (MNRAS 285, 806, 1997, submitted 1996 May 3), this paper has not previously appeared on the arXive. Despite its title, a prominent conclusion is that if the Universe is spatially flat, then the best cosmological parameters are Omega_m=0.2, Omega_Lambda=0.8, with probable range 0.1<Omega_m<0.3. It is the first in a series, the second being JCAP 0411(2004)007, astro-ph/0309390; the third is a recent preprint, astro-ph/060506

Decelerating universes older than their Hubble times

Recent observations suggest that Hubble's constant is large, and hence that the Universe appears to be younger than some of its constituents. The traditional escape route, which assumes that the expansion is accelerating, appears to be blocked by observations of Type 1a supernovae, which suggest(ed) that the Universe is decelerating. These observations are reconciled in a model in which the Universe has experienced an inflationary phase in the recent past, driven by an ultra-light inflaton whose Compton wavelength is of the same order as the Hubble radius.Comment: This paper, which predates the famous quintessence paper, has not previously appeared on the e-Print archive. It is essentially a quintessence model without eternal acceleration. Such models are now very topical in the context of string theory. 9 pages, 5 figure

What's up prof? Current issues in the visual effects &#38; post-production industry

We interviewed creative professionals at a number of London visual effects and post-production houses. We report on the key issues raised in those interviews: desirable new technologies, infrastructure challenges, personnel and process management

Autonomous Secondary Gaze Behaviours

In this paper we describe secondary behaviour, this is behaviour that is generated autonomously for an avatar. The user will control various aspects of the avatars behaviour but a truly expressive avatar must produce more complex behaviour than a user could specify in real time. Secondary behaviour provides some of this expressive behaviour autonomously. However, though it is produced autonomously it must produce behaviour that is appropriate to the actions that the user is controlling (the primary behaviour) and it must produce behaviour that corresponds to what the user wants. We describe an architecture which achieves these to aims by tagging the primary behaviour with messages to be sent to the secondary behaviour and by allowing the user to design various aspects of the secondary behaviour before starting to use the avatar. We have implemented this general architecture in a system which adds gaze behaviour to user designed actions

Policy instruments and greenhouse gas emissions from transport in the UK

A major focus of concern about the environment and the prospects for sustainable development is the transport sector. This sector has been growing rapidly, and growth is forecast to continue. Moreover, transport’s environmental consequences often appear to be difficult to control. In particular, transport is the fastest-growing contributor to greenhouse gas emissions in the UK, especially through the growth in road traffic. There is also concern about the health consequences of more localised emissions. In this paper, we review the impact of the sector on atmospheric pollution, and consider the alternative impacts of the different policy instruments available. The paper models the impact on passenger transport of the fiscal instruments adopted by the government, and contrasts them with alternative policies that have been advocated.

Integrating internal behavioural models with external expression

Users will believe in a virtual character more if they can empathise with it and understand what ‘makes it tick’. This will be helped by making the motivations of the character, and other processes that go towards creating its behaviour, clear to the user. This paper proposes that this can be achieved by linking the behavioural or cognitive system of the character to expressive behaviour. This idea is discussed in general and then demonstrated with an implementation that links a simulation of perception to the animation of a character’s eyes