3,295 research outputs found
Baryons and Skyrmions in QCD with Quarks in Higher Representations
We study the baryonic sector of QCD with quarks in the two index symmetric or
antisymmetric representation. The minimal gauge invariant state that carries
baryon number cannot be identified with the Skyrmion of the low energy chiral
effective Lagrangian. Mass, statistics and baryon number do not match. We
carefully investigate the properties of the minimal baryon in the large N limit
and we find that it is unstable under formation of bound states with higher
baryonic number. These states match exactly with the properties of the Skyrmion
of the effective Lagrangian.Comment: 23 pages, 13 figures. v2: minor changes. v3: corrected a mistake and
some typos. v4: modifyed the part about the stability of the Skyrmio
The Skyrmion strikes back: baryons and a new large limit
In the large limit of QCD, baryons can be modeled as solitons, for
instance, as Skyrmions. This modeling has been justified by Witten's
demonstration that all properties of baryons and mesons scale with
in the same way as the analogous meson-based soliton model scales with a
generic meson-meson coupling constant . An alternative large limit
(the orientifold large limit) has recently been proposed in which quarks
transform in the two-index antisymmetric representation of . By
carrying out the analog of Witten's analysis for the new orientifold large
limit, we show that baryons and solitons can also be identified in the
orientifold large limit. However, in the orientifold large limit,
the interaction amplitudes and matrix elements scale with in the
same way as soliton models scale with the generic meson coupling constant
rather than as as in the traditional large limit.Comment: 10 pages, 26 figure
Stable vs Unstable Vortices in SQCD
We give a topological classification of stable and unconfined massive
particles and strings (and some instantons) in worldvolume theories of
M5-branes and their dimensional reductions, generalizing Witten's
classification of strings in SYM. In particular 4d N=2 SQCD softly broken to
N=1 contains torsion (Douglas-Shenker) Z_N-strings and nontorsion (Hanany-Tong)
Z-strings. Some of the former are stable when the flavor symmetry is gauged,
while those that are not stable confine quarks and in some vacua even dyons
into baryons. The nontorsion strings are stable if and only if all colors are
locked to flavors, which is weaker than the BPS condition. As a byproduct
unstable string decay modes and approximate lifetimes are found. Cascading
theories have no vortices stabilized by the topological charges treated here
and in particular Gubser-Herzog-Klebanov axionic strings do not carry such a
charge.Comment: 32 pages, 6 figure
Compositional Performance Modelling with the TIPPtool
Stochastic process algebras have been proposed as compositional specification formalisms for performance models. In this paper, we describe a tool which aims at realising all beneficial aspects of compositional performance modelling, the TIPPtool. It incorporates methods for compositional specification as well as solution, based on state-of-the-art techniques, and wrapped in a user-friendly graphical front end. Apart from highlighting the general benefits of the tool, we also discuss some lessons learned during development and application of the TIPPtool. A non-trivial model of a real life communication system serves as a case study to illustrate benefits and limitations
Weak refinement in Z
An important aspect in the specification of distributed systems is the role of the internal (or unobservable) operation. Such operations are not part of the user interface (i.e. the user cannot invoke them), however, they are essential to our understanding and correct modelling of the system. Various conventions have been employed to model internal operations when specifying distributed systems in Z. If internal operations are distinguished in the specification notation, then refinement needs to deal with internal operations in appropriate ways. However, in the presence of internal operations, standard Z refinement leads to undesirable implementations.
In this paper we present a generalization of Z refinement, called weak refinement, which treats internal operations differently from observable operations when refining a system. We illustrate some of the properties of weak refinement through a specification of a telecommunications protocol
Cardiac magnetic resonance in cocaine-induced myocardial damage
A 54-year-old male with history of cocaine abuse underwent trans-thoracic echocardiography that showed hyper-echogenicity of the basal segments of the septum and infero-lateral wall of the left ventricle. The patient underwent cardiac CT that reported diffuse non-obstructive CAD. Cardiac MR showed LGE patterns consistent with non-ischemic myocardial damage associated with cocaine abuse
The Work of Roberto Busa SJ: Open Spaces between Computation and Hermeneutics
A review of the achievements of Fr. Busa over the course of his 60 years of work in the area of computational linguistics: internal hypertexts, the systematization of allographs, lemmatization, homographs and typologies; the lexical system; the laws of
economy for graphemes, for semantic typology, for heterogeneity among terms, and of the two lexical hemispheres. Finally, the project of disciplined languages is mentioned, a response to the linguistic challenge resulting from informational globalization
Magnetic Catalysis in AdS4
We study the formation of fermion condensates in Anti de Sitter space. In
particular, we describe a novel version of magnetic catalysis that arises for
fermions in asymptotically AdS4 geometries which cap off in the infra-red with
a hard wall. We show that the presence of a magnetic field induces a fermion
condensate in the bulk that spontaneously breaks CP symmetry. From the
perspective of the dual boundary theory, this corresponds to a strongly coupled
version of magnetic catalysis in d=2+1.Comment: 22 pages, 4 figures. v2: References added, factors of 2 corrected,
extra comments added in appendix. v3: extra comments about fermion modes in a
hard wall background. v4: A final factor of
Uncertainties on the /, / and / cross-section ratio from the modelling of nuclear effects and their impact on neutrino oscillation experiments
Recent studies have demonstrated non-trivial behaviours in the cross-section
extrapolation from () to
() interactions on nuclear targets in the charged-current
quasi-elastic (CCQE) regime. In this article, the potential for mis-modeling of
/, / and
/ cross-section ratios due to nuclear effects is
quantified by considering the model spread within the full kinematic phase
space for CCQE interactions. Its impact is then propagated to a simulated
experimental configuration based on the Hyper-K experiment, which is dominated
by CCQE interactions. Although a relatively large discrepancy between
theoretical models is confirmed for forward lepton angles at neutrino energies
below 300 MeV and for a new region of phase space at lepton angles above
, both regions are demonstrated to contribute a very small portion
of the Hyper-K (or T2K) flux integrated cross section. Overall, a systematic
uncertainty on the oscillated flux-averaged /
cross-section ratio is estimated to be 2%. A similar study was also
conducted for the proposed lower-energy ESSSB experiment configuration,
where the resulting uncertainty was found to be larger.Comment: 14 pages, 10 figures. Fixed abstract misformating on arxiv pag
Selective Adsorption of Ionic Species Using Macroporous Monodispersed Polyethylene Glycol Diacrylate/Acrylic Acid Microgels with Tunable Negative Charge
In this work, the possibility of fabricating composite magneto-optical ceramics by electrophoretic deposition (EPD) of nanopowders and high-temperature vacuum sintering of the compacts was investigated. Holmium oxide was chosen as a magneto-optical material for the study because of its transparency in the mid-IR range. Nanopowders of magneto-optical (Ho0.95La0.05)2O3 (HoLa) material were made by self-propagating high-temperature synthesis. Nanopowders of (Y0.9La0.1)2O3 (YLa) were made by laser synthesis for an inactive matrix. The process of formation of one- and two-layer compacts by EPD of the nanopowders from alcohol suspensions was studied in detail. Acetylacetone was shown to be a good dispersant to obtain alcohol suspensions of the nanopowders, characterized by high zeta potential values (+29â+80 mV), and to carry out a stable EPD process. One-layer compacts were made from the HoLa and YLa nanopowders with a density of 30â43%. It was found out that the introduction of polyvinyl butyral (PVB) into the suspension leads to a decrease in the mass and thickness of the green bodies deposited, but does not significantly affect their density. The possibility of making two-layer (YLa/HoLa) compacts with a thickness of up to 2.6 mm and a density of up to 46% was demonstrated. Sintering such compacts in a vacuum at a temperature of 1750 °C for 10 h leads to the formation of ceramics with a homogeneous boundary between the YLa/HoLa layers and a thickness of the interdiffused ion layer of about 30 ÎŒm
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