119 research outputs found
A System of Interaction and Structure
This paper introduces a logical system, called BV, which extends
multiplicative linear logic by a non-commutative self-dual logical operator.
This extension is particularly challenging for the sequent calculus, and so far
it is not achieved therein. It becomes very natural in a new formalism, called
the calculus of structures, which is the main contribution of this work.
Structures are formulae submitted to certain equational laws typical of
sequents. The calculus of structures is obtained by generalising the sequent
calculus in such a way that a new top-down symmetry of derivations is observed,
and it employs inference rules that rewrite inside structures at any depth.
These properties, in addition to allow the design of BV, yield a modular proof
of cut elimination.Comment: This is the authoritative version of the article, with readable
pictures, in colour, also available at
. (The published version contains
errors introduced by the editorial processing.) Web site for Deep Inference
and the Calculus of Structures at <http://alessio.guglielmi.name/res/cos
On the Length of Medial-Switch-Mix Derivations
International audienceSwitch and medial are two inference rules that play a central role in many deep inference proof systems. In specific proof systems, the mix rule may also be present. In this paper we show that the maximal length of a derivation using only the inference rules for switch, medial, and mix, modulo associativity and commutativity of the two binary con-nectives involved, is quadratic in the size of the formula at the conclusion of the derivation. This shows, at the same time, the termination of the rewrite system
Reionization History from Coupled CMB/21cm Line Data
We study CMB secondary anisotropies produced by inhomogeneous reionization by
means of cosmological simulations coupled with the radiative transfer code
CRASH. The reionization history is consistent with the WMAP Thomson optical
depth determination. We find that the signal arising from this process
dominates over the primary CMB component for l > 4000 and reaches a maximum
amplitude of l(l+1)C_l/2\pi ~ 1.6 x 10^{-13} on arcmin scale, i.e. l as large
as several thousands. We then cross-correlate secondary CMB anisotropy maps
with neutral hydrogen 21cm line emission fluctuations obtained from the same
simulations. The two signals are highly anti-correlated on angular scales
corresponding to the typical size of HII regions (including overlapping) at the
21cm map redshift. We show how the CMB/21cm cross-correlation can be used to:
(a) study the nature of the reionization sources, (b) reconstruct the cosmic
reionization history, (c) infer the mean cosmic ionization level at any
redshift. We discuss the feasibility of the proposed experiment with
forthcoming facilities.Comment: 7 pages, 5 figures, MNRAS in pres
Radiative Transfer Effects on the Lya Forest
Strong observational evidence for a fluctuating ultraviolet background (UVB)
has been accumulating through a number of studies of the HI and HeII Lya forest
as well as accurate IGM metallicity measurements. UVB fluctuations could arise
both from the inhomogeneous distribution of the ionizing sources and/or from
radiative transfer (RT) through the filamentary IGM. In this study we
investigate, via numerical simulations, the role of RT effects such as
shadowing, self-shielding and filtering of the ionizing radiation, in giving
raise to a fluctuating UVB. We focus on possible detectable signatures of these
effects on quantities derived from Lya forest spectra, as photoionization rate
fluctuations, eta parameter (the HeII to HI column density ratio) distributions
and the IGM temperature at redshift about 3. We find that RT induces
fluctuations up to 60% in the UVB, which are tightly correlated to the density
field. The UVB mean intensity is progressively suppressed toward higher
densities and photon energies above 4 Ryd, due to the high HeII opacity.
Shielding of overdense regions (Delta > 5) from cosmic HeII ionizing radiation,
produces a decreaseing trend of eta with overdensity. Furthermore we find that
the mean eta value inferred from HI-HeII Lya forest observations can be
explained only by properly accounting for the actual IGM opacity. We outline
and discuss several implications of our findings.Comment: 13 pages, 10 figures, Accepted for publication in MNRA
Cosmological Reionization Around the First Stars: Monte Carlo Radiative Transfer
We study the evolution of ionization fronts around the first proto-galaxies
by using high resolution numerical cosmological (Lambda+CDM model) simulations
and Monte Carlo radiative transfer methods. We present the numerical scheme in
detail and show the results of test runs from which we conclude that the scheme
is both fast and accurate. As an example of interesting cosmological
application, we study the reionization produced by a stellar source of total
mass M=2 10^8 M_\odot turning on at z=12, located at a node of the cosmic web.
The study includes a Spectral Energy Distribution of a zero-metallicity stellar
population, and two Initial Mass Functions (Salpeter/Larson). The expansion of
the I-front is followed as it breaks out from the galaxy and it is channeled by
the filaments into the voids, assuming, in a 2D representation, a
characteristic butterfly shape. The ionization evolution is very well tracked
by our scheme, as realized by the correct treatment of the channeling and
shadowing effects due to overdensities. We confirm previous claims that both
the shape of the IMF and the ionizing power metallicity dependence are
important to correctly determine the reionization of the universe.Comment: 8 pages, 8 figures. Revised version, accepted for publication by
MNRA
Cosmic Microwave Background Polarization and reionization: constraining models with a double reionization
Neutral hydrogen around high-z QSO and an optical depth tau ~ 0.17 can be
reconciled if reionization is more complex than a single transition at z ~ 6-8.
Tracing its details could shed a new light on the first sources of radiation.
Here we discuss how far such details can be inspected through planned
experiments on CMB large-scale anisotropy and polarization, by simulating an
actual data analysis. By considering a set of double reionization histories of
Cen (2003) type, a relevant class of models not yet considered by previous
works, we confirm that large angle experiments rival high resolution ones in
reconstructing the reionization history. We also confirm that reionization
histories, studied with the prior of a single and sharp reionization, yield a
biased tau, showing that this bias is generic. We further find a monotonic
trend in the bias for the models that we consider, and propose an explanation
of the trend, as well as the overall bias. We also show that in long-lived
experiments such a trend can be used to discriminate between single and double
reionization patterns.Comment: 8 pages, 11 figures. Substantial rewriting, replaced with accepted
version. To be published in A&
Hydrodynamical simulations of the Sunyaev–Zel'dovich effect: the kinetic effect
We use hydrodynamical N-body simulations to study the kinetic Sunyaev–Zel'dovich effect. We construct sets of maps, one square degree in size, in three different cosmological models. We confirm earlier calculations that on the scales studied the kinetic effect is much smaller than the thermal (except close to the thermal null point), with an rms dispersion smaller by about a factor of 5 in the Rayleigh–Jeans region. We study the redshift dependence of the rms distortion and the pixel distribution at the present epoch. We compute the angular power spectra of the maps, including their redshift dependence, and compare them with the thermal Sunyaev–Zel'dovich effect and with the expected cosmic microwave background anisotropy spectrum as well as with determinations by other authors. We correlate the kinetic effect with the thermal effect both pixel-by-pixel and for identified thermal sources in the maps to assess the extent to which the kinetic effect is enhanced in locations of strong thermal signal
Development of a loop-mediated isothermal amplification (LAMP) assay for the identification of the invasive wood borer Aromia bungii (Coleoptera: Cerambycidae) from frass
The red-necked longhorn beetle Aromia bungii (Faldermann, 1835) (Coleoptera: Cerambycidae) is native to east Asia, where it is a major pest of cultivated and ornamental species of the genus Prunus. Morphological or molecular discrimination of adults or larval specimens is required to identify this invasive wood borer. However, recovering larval stages of the pest from trunks and branches causes extensive damage to plants and is timewasting. An alternative approach consists in applying non-invasive molecular diagnostic tools to biological traces (i.e., fecal pellets, frass). In this way, infestations in host plants can be detected without destructive methods. This paper presents a protocol based on both real-time and visual loop-mediated isothermal amplification (LAMP), using DNA of A. bungii extracted from fecal particles in larval frass. Laboratory validations demonstrated the robustness of the protocols adopted and their reliability was confirmed performing an inter-lab blind panel. The LAMP assay and the qPCR SYBR Green method using the F3/B3 LAMP external primers were equally sensitive, and both were more sensitive than the conventional PCR (sensitivity > 103 to the same starting matrix). The visual LAMP protocol, due to the relatively easy performance of the method, could be a useful tool to apply in rapid monitoring of A. bungii and in the management of its outbreaks
Foregrounds for observations of the cosmological 21 cm line: I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field
We present the first results from a series of observations conducted with the
Westerbork telescope in the 140--160 MHz range with a 2 arcmin resolution aimed
at characterizing the properties of the foregrounds for epoch of reionization
experiments. For the first time we have detected fluctuations in the Galactic
diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low
Galactic latitude area known as Fan region. Those fluctuations have an of
14 K. The total intensity power spectrum shows a power--law behaviour down to
with slope . The detection of
diffuse emission at smaller angular scales is limited by residual point
sources. We measured an confusion noise of 3 mJy beam.
Diffuse polarized emission was also detected for the first time at this
frequency. The polarized signal shows complex structure both spatially and
along the line of sight. The polarization power spectrum shows a power--law
behaviour down to with slope .
The of polarization fluctuations is 7.2 K on 4 arcmin scales. By
extrapolating the measured spectrum of total intensity emission, we find a
contamination on the cosmological signal of K on 5 arcmin scales and a corresponding value
of 18.3 K at the same angular scale. The level of the polarization power
spectrum is K on 5 arcmin scales. Given its exceptionally
bright polarized signal, the Fan region is likely to represent an upper limit
on the sky brightness at moderate and high Galactic latitude.Comment: Minor corrections made to match the final version printed on A&A. A
version with high resolution figures is available at
http://www.astro.rug.nl/~bernardi/FAN/fan.pd
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