306 research outputs found
Measuring the proton spectrum in neutron decay - latest results with aSPECT
The retardation spectrometer aSPECT was built to measure the shape of the
proton spectrum in free neutron decay with high precision. This allows us to
determine the antineutrino electron angular correlation coefficient a. We aim
for a precision more than one order of magnitude better than the present best
value, which is Delta_a /a = 5%.
In a recent beam time performed at the Institut Laue-Langevin during April /
May 2008 we reached a statistical accuracy of about 2% per 24 hours measurement
time. Several systematic effects were investigated experimentally. We expect
the total relative uncertainty to be well below 5%.Comment: Accepted for publication in the Conference Proceedings of the
International Workshop on Particle Physics with Slow Neutrons 2008 held at
the ILL, France. To be published in Nuclear Instruments and Methods in
Physics Research, Section
Descriptions of membrane mechanics from microscopic and effective two-dimensional perspectives
Mechanics of fluid membranes may be described in terms of the concepts of
mechanical deformations and stresses, or in terms of mechanical free-energy
functions. In this paper, each of the two descriptions is developed by viewing
a membrane from two perspectives: a microscopic perspective, in which the
membrane appears as a thin layer of finite thickness and with highly
inhomogeneous material and force distributions in its transverse direction, and
an effective, two-dimensional perspective, in which the membrane is treated as
an infinitely thin surface, with effective material and mechanical properties.
A connection between these two perspectives is then established. Moreover, the
functional dependence of the variation in the mechanical free energy of the
membrane on its mechanical deformations is first studied in the microscopic
perspective. The result is then used to examine to what extent different,
effective mechanical stresses and forces can be derived from a given, effective
functional of the mechanical free energy.Comment: 37 pages, 3 figures, minor change
Categorical Tinkertoys for N=2 Gauge Theories
In view of classification of the quiver 4d N=2 supersymmetric gauge theories,
we discuss the characterization of the quivers with superpotential (Q,W)
associated to a N=2 QFT which, in some corner of its parameter space, looks
like a gauge theory with gauge group G. The basic idea is that the Abelian
category rep(Q,W) of (finite-dimensional) representations of the Jacobian
algebra should enjoy what we call the Ringel
property of type G; in particular, rep(Q,W) should contain a universal
`generic' subcategory, which depends only on the gauge group G, capturing the
universality of the gauge sector. There is a family of 'light' subcategories
, indexed by points , where
is a projective variety whose irreducible components are copies of
in one--to--one correspondence with the simple factors of G.
In particular, for a Gaiotto theory there is one such family of
subcategories, , for each maximal degeneration of
the corresponding surface , and the index variety may be identified
with the degenerate Gaiotto surface itself: generic light subcategories
correspond to cylinders, while closed-point subcategories to `fixtures'
(spheres with three punctures of various kinds) and higher-order
generalizations. The rules for `gluing' categories are more general that the
geometric gluing of surfaces, allowing for a few additional exceptional N=2
theories which are not of the Gaiotto class.Comment: 142 pages, 8 figures, 5 table
On Arnold's 14 `exceptional' N=2 superconformal gauge theories
We study the four-dimensional superconformal N=2 gauge theories engineered by
the Type IIB superstring on Arnold's 14 exceptional unimodal singularities
(a.k.a. Arnold's strange duality list), thus extending the methods of 1006.3435
to singularities which are not the direct sum of minimal ones. In particular,
we compute their BPS spectra in several `strongly coupled' chambers.
From the TBA side, we construct ten new periodic Y-systems, providing
additional evidence for the existence of a periodic Y-system for each isolated
quasi-homogeneous singularity with (more generally, for each N=2
superconformal theory with a finite BPS chamber whose chiral primaries have
dimensions of the form N/l).Comment: 73 pages, 7 figure
Elastic deformation of a fluid membrane upon colloid binding
When a colloidal particle adheres to a fluid membrane, it induces elastic
deformations in the membrane which oppose its own binding. The structural and
energetic aspects of this balance are theoretically studied within the
framework of a Helfrich Hamiltonian. Based on the full nonlinear shape
equations for the membrane profile, a line of continuous binding transitions
and a second line of discontinuous envelopment transitions are found, which
meet at an unusual triple point. The regime of low tension is studied
analytically using a small gradient expansion, while in the limit of large
tension scaling arguments are derived which quantify the asymptotic behavior of
phase boundary, degree of wrapping, and energy barrier. The maturation of
animal viruses by budding is discussed as a biological example of such
colloid-membrane interaction events.Comment: 14 pages, 9 figures, REVTeX style, follow-up on cond-mat/021242
Gorenstein homological algebra and universal coefficient theorems
We study criteria for a ring—or more generally, for a small category—to be Gorenstein and for a module over it to be of finite projective dimension. The goal is to unify the universal coefficient theorems found in the literature and to develop machinery for proving new ones. Among the universal coefficient theorems covered by our methods we find, besides all the classic examples, several exotic examples arising from the KK-theory of C*-algebras and also Neeman’s Brown–Adams representability theorem for compactly generated categories
Cycle-finite module categories
We describe the structure of module categories of finite dimensional algebras
over an algebraically closed field for which the cycles of nonzero
nonisomorphisms between indecomposable finite dimensional modules are finite
(do not belong to the infinite Jacobson radical of the module category).
Moreover, geometric and homological properties of these module categories are
exhibited
Family doctors' problems and motivating factors in management of depression
BACKGROUND: Depression is a frequent psychiatric disorder, and depressive patient may be more problematic for the family doctors (FD) than a patient suffering from a somatic disease. Treatment of patients with depressive disorders is a relatively new task for Estonian FDs. The aim of our study was to find out the family doctors' attitudes to depression related problems, their readiness, motivating factors and problems in the treatment of depressive patients as well as the existence of relevant knowledge. METHODS: In 2002, altogether 500 FDs in Estonia were invited to take part in a tailor-made questionnaire survey, of which 205 agreed to participate. RESULTS: Of the respondents 185(90%) considered management of depressive patients and their treatment to be the task of FDs. One hundred and eighty FDs (88%) were themselves ready to deal with depressed patients, and 200(98%) of them actually treated such patients. Commitment to the interests of the patients, better cooperation with successfully treated patients, the patients' higher confidence in FDs and disappearance of somatic complaints during the treatment of depression were the motivating factors for FDs. FDs listed several important problems interfering with their work with depressive patients: limited time for one patient, patients' attitudes towards the diagnosis of depression, doctors' difficulties to change the underlying causes of depression, discontinuation of the treatment due to high expenses and length. Although 115(56%) respondents maintained that they had sufficient knowledge for diagnostics and treatment of depression, 181(88%) were of the opinion that they needed additional training. CONCLUSION: FDs are ready to manage patients who might suffer from depression and are motivated by good doctor-patient relationship. However, majority of them feel that they need additional training
4d N=2 Gauge Theories and Quivers: the Non-Simply Laced Case
We construct the BPS quivers with superpotential for the 4d N=2 gauge
theories with non-simply laced Lie groups (B_n, C_n, F_4 and G_2). The
construction is inspired by the BIKMSV geometric engineering of these gauge
groups as non-split singular elliptic fibrations. From the categorical
viewpoint of arXiv:1203.6743, the fibration of the light category L(g) over the
(degenerate) Gaiotto curve has a monodromy given by the action of the outer
automorphism of the corresponding unfolded Lie algebra. In view of the
Katz--Vafa `matter from geometry' mechanism, the monodromic idea may be
extended to the construction of (Q, W) for SYM coupled to higher matter
representations. This is done through a construction we call specialization.Comment: 42 pages, 2 figure
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