33,720 research outputs found
X-ray bright groups and their galaxies
Combining X-ray data from the ROSAT PSPC and optical data drawn from the
literature, we examine in detail the relationship between the X-ray and optical
properties of X-ray bright galaxy groups. We find a relationship between
optical luminosity and X-ray temperature consistent with that expected from
self-similar scaling of galaxy systems, L_B \propto T^{1.6 +/- 0.2}. The
self-similar form and continuity of the L_B : T relation from clusters to
groups and the limited scatter seen in this relation, implies that the star
formation efficiency is rather similar in all these systems. We find that the
bright extended X-ray components associated with many central galaxies in
groups appear to be more closely related to the group than the galaxy itself,
and we suggest that these are group cooling flows rather than galaxy halos. In
addition we find that the optical light in these groups appears to be more
centrally concentrated than the light in clusters. We also use the optical and
X-ray data to investigate whether early or late type galaxies are primarily
responsible for preheating in groups. Using three different methods, we
conclude that spiral galaxies appear to play a comparable role to early types
in the preheating of the intragroup medium. This tends to favour models in
which the preheating arises primarily from galaxy winds rather than AGN, and
implies that spirals have played a significant role in the metal enrichment of
the intragroup medium.Comment: 17 pages, accepted for publication in MNRA
An SUSY GUT of flavour in 6d
We propose a 6d model with a SUSY gauge symmetry. After
compactification, it explains the origin of the Family Symmetry with CSD3
vacuum alignment, as well as breaking with doublet-triplet splitting.
The model naturally accounts for all quark and lepton (including neutrino)
masses and mixings, incorporating the highly predictive Littlest Seesaw
structure. It spontaneously breaks CP symmetry, resulting in successful CP
violation in the quark and lepton sectors, while solving the Strong CP problem.
It also explains the Baryon Asymmetry of the Universe (BAU) through
leptogenesis, with the leptogenesis phase directly linked to the Dirac and
Majorana phases.Comment: 23 pages, 6 figures. v3: Version published in JHE
The global nuclear liability regime post Fukushima Daiichi
Nuclear liability regimes are important as they ensure that potential victims will be compensated promptly and efficiently after a nuclear accident. The accident at Fukushima Daiichi in Japan in 2011 prompted a review of the global nuclear liability regime that remains on-going. Progress has been slow, but over the next few years the European Union is set to announce its new proposals. Meanwhile, in 2015, another global nuclear liability regime, the Convention on Supplementary Compensation for Nuclear Damage, has entered into force. This paper aims to move the debate in the literature on nuclear liability and focuses on the four following major issues: (1) reviews third-party nuclear liability regimes currently in operation around the world; (2) analyses the international nuclear liability regime following the accident at Fukushima Daiichi; (3) comparatively assesses the liability regimes for nuclear energy and the non-nuclear energy sector; and (4) presents the future outlook for possible developments in the global nuclear liability regime
Higgs transitions of spin ice
Frustrated magnets such as spin ice exhibit Coulomb phases, where
correlations have power-law forms at long distances. Applied perturbations can
cause ordering transitions which cannot be described by the usual Landau
paradigm, and are instead naturally viewed as Higgs transitions of an emergent
gauge theory. Starting from a classical statistical model of spin ice, it is
shown that a variety of possible phases and transitions can be described by
this approach. Certain cases are identified where continuous transitions are
argued to be likely; the predicted critical behavior may be tested in
experiments or numerical simulations.Comment: 23 pages, 10 figures; v2: published version with minor changes;
ancillary file "Figures3D.nb" is a Mathematica (v7) notebook containing
figures as rotatable 3D graphics (see http://www.wolfram.com/cdf-player/ for
a free viewer
Generalised CP and Family Symmetry
We perform a comprehensive study of family symmetry models based on
combined with the generalised CP symmetry . We investigate the
lepton mixing parameters which can be obtained from the original symmetry
breaking to different remnant symmetries in the
neutrino and charged lepton sectors. We find that only one case is
phenomenologically viable, namely in the neutrino sector and in the charged lepton sector, leading to the
prediction of no CP violation, namely and the Majorana phases
and are all equal to either zero or . We then
propose an effective supersymmetric model based on the symmetry in which trimaximal lepton mixing is predicted together with
either zero CP violation or with non-trivial
Majorana phases. An ultraviolet completion of the effective model yields a
neutrino mass matrix which depends on only three real parameters. As a result
of this, all three CP phases and the absolute neutrino mass scale are
determined, the atmospheric mixing angle is maximal, and the Dirac CP can
either be preserved with or maximally broken with
and sharp predictions for the Majorana phases and
neutrinoless double beta decay.Comment: 38 pages, 3 figure
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