52,328 research outputs found
Multi-Wavelength Observations of Short-Duration Gamma-Ray Bursts: Recent Results
The number of detections as well as significantly deep non-detections of
optical/NIR afterglows of Type I (short-duration population) Gamma-Ray Bursts
(GRBs) has become large enough that statistically meaningful samples can now be
constructed. I present within some recent results on the luminosity
distribution of Type I GRB afterglows in comparison to those of Type II GRBs
(collapsar population), the issue of the existence of jet breaks in Type I GRB
afterglows, and the discovery of dark Type I GRBs.Comment: 10 pages, 3 figures, based on an invited talk, to appear in the
proceedings of the Gamma-Ray Burst Symposium 2012- IAA-CSIC - Marbella,
editors: Castro-Tirado, A. J., Gorosabel, J. and Park, I. H; v2: accepted,
slightly expanded, minor changes after referee repor
Developing organic production in Northern Ireland
This report was presented at the UK Organic Research 2002 Conference. The area of land under organic management in Northern Ireland has increased from 215 ha in January 1998 to 5,000 ha in December 2001. The Minister for the Department of Agriculture and Rural Development (DARD) has set a target for organic farming of 30,000 ha by 2006 and also commissioned an independent study of the strategic needs for developing the Northern Ireland organic sector in 2000. Greenmount College have taken the decision to establish an organic unit to support these DARD initiatives for organic farming and implement key recommendations from the strategy. The College has also initiated a project to gather and analyse data from 45 organic and in-conversion farms over a three-year period. This data will be used to benchmark organic production and assist with conversion and development of the sector
Pseudomodes and the corresponding transformation of the temperature-dependent bath correlation function
In open system approaches with non-Markovian environments, the process of
inserting an individual mode (denoted as "pseudomode") into the bath or
extracting it from the bath is widely employed. This procedure, however, is
typically performed on basis of the spectral density (SD) and does not
incorporate temperature. Here, we show how the - temperature-dependent - bath
correlation function (BCF) transforms in such a process. We present analytic
formulae for the transformed BCF and numerically study the differences between
factorizing initial state and global thermal (correlated) initial state of mode
and bath, respectively. We find that in the regime of strong coupling of the
mode to both system and bath, the differences in the BCFs give rise to
pronounced differences in the dynamics of the system.Comment: 12 pages, 4 figure
Multiclass multiserver queueing system in the Halfin-Whitt heavy traffic regime. Asymptotics of the stationary distribution
We consider a heterogeneous queueing system consisting of one large pool of
identical servers, where is the scaling parameter. The
arriving customers belong to one of several classes which determines the
service times in the distributional sense. The system is heavily loaded in the
Halfin-Whitt sense, namely the nominal utilization is where
is the spare capacity parameter. Our goal is to obtain bounds on the
steady state performance metrics such as the number of customers waiting in the
queue . While there is a rich literature on deriving process level
(transient) scaling limits for such systems, the results for steady state are
primarily limited to the single class case.
This paper is the first one to address the case of heterogeneity in the
steady state regime. Moreover, our results hold for any service policy which
does not admit server idling when there are customers waiting in the queue. We
assume that the interarrival and service times have exponential distribution,
and that customers of each class may abandon while waiting in the queue at a
certain rate (which may be zero). We obtain upper bounds of the form
on both and the number of idle servers. The bounds
are uniform w.r.t. parameter and the service policy. In particular, we show
that . Therefore, the
sequence is tight and has a uniform exponential tail
bound. We further consider the system with strictly positive abandonment rates,
and show that in this case every weak limit of
has a sub-Gaussian tail. Namely .Comment: 21 page
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