155 research outputs found
Gauge Theories on Deformed Spaces
The aim of this review is to present an overview over available models and
approaches to non-commutative gauge theory. Our main focus thereby is on gauge
models formulated on flat Groenewold-Moyal spaces and renormalizability, but we
will also review other deformations and try to point out common features. This
review will by no means be complete and cover all approaches, it rather
reflects a highly biased selection.Comment: v2 references added; v3 published versio
A multilevel approach to energy options across EU: the role of supra-national governance, values and trust
WOS:000328235800004 (Nº de Acesso Web of Science)The European Union (EU) has in the last decades proposed several policies to promote sustainable forms of energy production. This topic brings together environmental concerns and technological innovation, two domains traditionally seen as opposite. To help understand how the publics mobilize for this debate, we examined the Science & Technology (S&T) and Public Understanding of Science (PUS) 2010 Eurobarometer resorting to a multi-level approach. We examined the role of cultural aspects, like worldviews and institutional trust, and country-level distinctions, namely the stage of accession to EU. Results show that egalitarians are more supportive of solar energy and less supportive of nuclear energy than hierarchics, although support for both technologies is (positively) predicted mainly by institutional trust. Active involvement in S&T and Environmental matters relies mostly on awareness about environmental problems, but is also related to believing technology will provide inexhaustible resources. At the contextual-level, newer EU member-states are less supportive of solar energy, more supportive of nuclear energy and less actively engaged in civic participation than older member-states. The findings highlight the intricate liaison between environmental and technological matters in the public debate about energy production and bring to the fore the relevance of legal innovation as determinant of value change
Quantum Corrections for Translation-Invariant Renormalizable Non-Commutative Phi^4 Theory
In this paper we elaborate on the translation-invariant renormalizable Phi^4
theory in 4-dimensional non-commutative space which was recently introduced by
the Orsay group. By explicitly performing Feynman graph calculations at one
loop and higher orders we illustrate the mechanism which overcomes the UV/IR
mixing problem and ultimately leads to a renormalizable model. The obtained
results show that the IR divergences are also suppressed in the massless case,
which is of importance for the gauge field theoretic generalization of the
scalar field model.Comment: 18 pages, v2: slightly extended version including a new section on
one-loop renormalization, v3: minor revisio
A New Approach to Non-Commutative U(N) Gauge Fields
Based on the recently introduced model of arXiv:0912.2634 for non-commutative
U(1) gauge fields, a generalized version of that action for U(N) gauge fields
is put forward. In this approach to non-commutative gauge field theories, UV/IR
mixing effects are circumvented by introducing additional 'soft breaking' terms
in the action which implement an IR damping mechanism. The techniques used are
similar to those of the well-known Gribov-Zwanziger approach to QCD.Comment: 11 pages; v2 minor correction
Commutative limit of a renormalizable noncommutative model
Renormalizable models on Moyal space have been obtained by
modifying the commutative propagator. But these models have a divergent "naive"
commutative limit. We explain here how to obtain a coherent such commutative
limit for a recently proposed translation-invariant model. The mechanism relies
on the analysis of the uv/ir mixing in general Feynman graphs.Comment: 11 pages, 3 figures, minor misprints being correcte
A SINFONI view of flies in the Spiderweb: a galaxy cluster in the making
The environment of the high-z radio galaxy PKS 1138-262 at z~2.2 is a prime
example of a forming galaxy cluster. We use deep SINFONI data to perform a
detailed study of the kinematics of the galaxies within 60 kpc of the radio
core and we link this to the kinematics of the protocluster on the megaparsec
scale. Identification of optical emission lines shows that 11 galaxies are at
the redshift of the protocluster. The density of line emitters is more than an
order of magnitude higher in the core of the protocluster than the larger scale
environment. This implies a matter overdensity in the core of delta_m~70 which
is similar to the outskirts of local galaxy clusters. The velocity distribution
of the confirmed satellite galaxies shows a broad, double-peaked velocity
structure with sigma=1360+/-206 km/s. A similar broad, double-peaked
distribution was found in a previous study targeting the large scale
protocluster structure, indicating that a common process is acting on both
small and large scales. Including all spectroscopically confirmed protocluster
galaxies, a velocity dispersion of 1013+/-87 km/s is found. We show that the
protocluster has likely decoupled from the Hubble flow and is a dynamically
evolved structure. Comparison to the Millenium simulation indicates that the
protocluster velocity distribution is consistent with that of the most massive
haloes at z~2, but we rule out that the protocluster is a fully virialized
structure based on dynamical arguments and its X-ray luminosity. Comparison to
merging haloes in the Millennium simulation shows that the structure as
observed in and around the Spiderweb galaxy is best interpreted as being the
result of a merger between two massive haloes. We propose that this merger can
result in an increase in star formation and AGN activity in the protocluster
core and is possibly an important stage in the evolution of massive cD
galaxies.Comment: 12 pages, 7 figures. Accepted for publication in MNRA
Translation-invariant models for non-commutative gauge fields
Motivated by the recent construction of a translation-invariant
renormalizable non-commutative model for a scalar field (see arXiv:0802.0791
[math-ph]), we introduce models for non-commutative U(1) gauge fields along the
same lines. More precisely, we include some extra terms into the action with
the aim of getting rid of the UV/IR mixing.Comment: 9 page
Globules and pillars seen in the [CII] 158 micron line with SOFIA
Molecular globules and pillars are spectacular features, found only in the
interface region between a molecular cloud and an HII-region. Impacting
Far-ultraviolet (FUV) radiation creates photon dominated regions (PDRs) on
their surfaces that can be traced by typical cooling lines. With the GREAT
receiver onboard SOFIA we mapped and spectrally resolved the [CII] 158 micron
atomic fine-structure line and the highly excited 12CO J=11-10 molecular line
from three objects in Cygnus X (a pillar, a globule, and a strong IRAS source).
We focus here on the globule and compare our data with existing Spitzer data
and recent Herschel Open-Time PACS data. Extended [CII] emission and more
compact CO-emission was found in the globule. We ascribe this emission mainly
to an internal PDR, created by a possibly embedded star-cluster with at least
one early B-star. However, external PDR emission caused by the excitation by
the Cyg OB2 association cannot be fully excluded. The velocity-resolved [CII]
emission traces the emission of PDR surfaces, possible rotation of the globule,
and high-velocity outflowing gas. The globule shows a velocity shift of ~2 km/s
with respect to the expanding HII-region, which can be understood as the
residual turbulence of the molecular cloud from which the globule arose. This
scenario is compatible with recent numerical simulations that emphazise the
effect of turbulence. It is remarkable that an isolated globule shows these
strong dynamical features traced by the [CII]-line, but it demands more
observational studies to verify if there is indeed an embedded cluster of
B-stars.Comment: Letter accepted by A&A (SOFIA special issue
Evidence for powerful AGN winds at high redshift: Dynamics of galactic outflows in radio galaxies during the "Quasar Era"
AGN feedback now appears as an attractive mechanism to resolve some of the
outstanding problems with the "standard" cosmological models, in particular
those related to massive galaxies. To directly constrain how this may influence
the formation of massive galaxies near the peak in the redshift distribution of
powerful quasars, z~2, we present an analysis of the emission-line kinematics
of 3 powerful radio galaxies at z~2-3 (HzRGs) based on rest-frame optical
integral-field spectroscopy obtained with SINFONI on the VLT. HzRGs are among
the most massive galaxies, so AGN feedback may have a particularly clear
signature. We find evidence for bipolar outflows in all HzRGs, with kinetic
energies that are equivalent to 0.2% of the rest-mass of the supermassive black
hole. Velocity offsets in the outflows are ~800-1000 km s^-1 between the
blueshifted and redshifted line emission, FWHMs ~1000 km s^-1 suggest strong
turbulence. Ionized gas masses estimated from the Ha luminosity are of order
10^10 M_s, similar to the molecular gas content of HzRGs, underlining that
these outflows may indicate a significant phase in the evolution of the host
galaxy. The total energy release of ~10^60 erg during a dynamical time of ~10^7
yrs corresponds to about the binding energy of a massive galaxy. Geometry,
timescales and energy injection rates of order 10% of the kinetic energy flux
of the jet suggest that the outflows are most likely driven by the radio
source. The global energy density release of ~10^57 erg s^-1 Mpc^-3 may also
influence the subsequent evolution of the HzRG by enhancing the entropy and
pressure in the surrounding halo and facilitating ram-pressure stripping of gas
in satellite galaxies that may contribute to the subsequent mass assembly of
the HzRG through low-dissipation "dry" mergers.Comment: A&A in press, minor edits & typo in table captions 2-
Bottom up ethics - neuroenhancement in education and employment
Neuroenhancement involves the use of neurotechnologies to improve cognitive, affective or behavioural functioning, where these are not judged to be clinically impaired. Questions about enhancement have become one of the key topics of neuroethics over the past decade. The current study draws on in-depth public engagement activities in ten European countries giving a bottom-up perspective on the ethics and desirability of enhancement. This informed the design of an online contrastive vignette experiment that was administered to representative samples of 1000 respondents in the ten countries and the United States. The experiment investigated how the gender of the protagonist, his or her level of performance, the efficacy of the enhancer and the mode of enhancement affected support for neuroenhancement in both educational and employment contexts. Of these, higher efficacy and lower performance were found to increase willingness to support enhancement. A series of commonly articulated claims about the individual and societal dimensions of neuroenhancement were derived from the public engagement activities. Underlying these claims, multivariate analysis identified two social values. The Societal/Protective highlights counter normative consequences and opposes the use enhancers. The Individual/Proactionary highlights opportunities and supports use. For most respondents these values are not mutually exclusive. This suggests that for many neuroenhancement is viewed simultaneously as a source of both promise and concern
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