49,681 research outputs found
't Hooft loop and the phases of SU(2) LGT
We analyze the vacuum structure of SU(2) lattice gauge theories in D=2,3,4,
concentrating on the stability of 't Hooft loops. High precision calculations
have been performed in D=3; similar results hold also for D=4 and D=2. We
discuss the impact of our findings on the continuum limit of Yang-Mills
theories.Comment: 7 pages, 3 figures. Presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Twistors and Spin 3/2 Potentials in Quantum Gravity
Local boundary conditions involving field strengths and the normal to the
boundary, originally studied in anti-de Sitter space-time, have been recently
considered in one-loop quantum cosmology. This paper derives the conditions
under which spin-lowering and spin-raising operators preserve these local
boundary conditions on a 3-sphere for fields of spin 0,1/2,1,3/2 and 2.
Moreover, the two-component spinor analysis of the four potentials of the
totally symmetric and independent field strengths for spin 3/2 is applied to
the case of a 3-sphere boundary. It is shown that such boundary conditions can
only be imposed in a flat Euclidean background, for which the gauge freedom in
the choice of the potentials remains. Alternative boundary conditions for
supergravity involving the spinor-valued 1-forms for gravitinos and the normal
to the boundary are also studied.Comment: 20 pages, plain-tex, recently appearing in: Twistor Theory, edited by
Stephen Huggett (Marcel Dekker, New York, 1994). The authors apologize for
the delay in circulating the paper, which was due to technical problems now
fixe
5-Hydroxy-3-(4-hydroxyphenyl)-8,8-dimethyl-6- (3-methylbut-2-enyl)pyrano[2,3-h]chromen-4-one
Natural and semi-synthetic compounds are being studied as novel phosphodiesterase 5 (PDE5) inhibitors for the treatment of erectile dysfunction, pulmonary hypertension, and lower urinary symptoms. Maclura pomifera is a source of flavonoids, one of the main classes of molecules investigated for these purposes. The extraction of the natural isoflavone osajin and its modification to obtain a semi-synthetic derivative are described in this short note. 1H and 13C-nuclear magnetic resonance spectroscopy (NMR), mass spectrometry, high-performance liquid chromatography (HPLC) and spectroscopic characterization of the title compound are also hereby provided. Two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY) NMR, supported by in silico conformational studies, was used to achieve a complete assignment of the proton signals, assessing the correct chemical structure of the compound. Heteronuclear single quantum coherence spectroscopy (HSQC) and heteronuclear multiple bond correlation (HMBC) NMR experiments were performed to assign 13C chemical shifts. Calculated chemical properties and preliminary in silico docking suggest that this molecule might be a promising candidate as PDE5 inhibitor
Improved-Accuracy Source Reconstructionon Arbitrary 3-D Surfaces
This paper presents a novel formulation of the source reconstruction problem on arbitrary three-dimensional (3-D) surfaces based on integral equations. Rigorous boundary integral field identities are employed to enforce that the two unknown currents are Maxwellian on the reconstruction surface; this leads to a dual integral-equation formulation, in contrast to the single-equation formulation found in literature. Numerical tests against reference currents allow a quantitative assessment of the improvements in accuracy afforded by the novel formulation, with important benefits in diagnostic application
From physics to biology by extending criticality and symmetry breakings
Symmetries play a major role in physics, in particular since the work by E. Noether and H. Weyl in the first half of last century. Herein, we briefly review their role by recalling how symmetry changes allow to conceptually move from classical to relativistic and quantum physics. We then introduce our ongoing theoretical analysis in biology and show that symmetries play a radically different role in this discipline, when compared to those in current physics. By this comparison, we stress that symmetries must be understood in relation to conservation and stability properties, as represented in the theories. We posit that the dynamics of biological organisms, in their various levels of organization, are not just processes, but permanent (extended, in our terminology) critical transitions and, thus, symmetry changes. Within the limits of a relative structural stability (or interval of viability), variability is at the core of these transitions
Direction dependent free energy singularity of the asymmetric six-vertex model
The transition from the ordered commensurate phase to the incommensurate
gaussian phase of the antiferroelectric asymmetric six-vertex model is
investigated by keeping the temperature constant below the roughening point and
varying the external fields . In the plane, the phase boundary
is approached along straight lines , where measures the displacement from the phase boundary. It is found
that the free energy singularity displays the exponent 3/2 typical of the
Pokrovski-Talapov transition for any
direction other than the tangential one. In the latter case shows a
discontinuity in the third derivative.Comment: 18 pages, Latex, 1 figure, minor corrections and two references
change
Selected Items in Jet Algorithms
I provide a very brief overview of recent developments in jet algorithms,
mostly focusing on the issue of infrared-safety.Comment: 3 pages. Talk given at IFAE 2008, Bologna, Italy, 26-28 March 200
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