1,478 research outputs found
Notes of an IIASA Colloquium
Urban and regional planning are of such importance that they cannot be delegated to city planners or architects. They constitute tasks of sociological, psychological and environmental natures which do not lend themselves to the capabilities of "know-how, know-where, know-when specialists." They are, on the other hand, a promising field for the efforts of those who have gained experience in systems analysis -- of groups and teams similar to those that IIASA represents
Going to the Other Side via the Resurgent Bridge
Using resurgent analysis we offer a novel mathematical perspective on a
curious bijection (duality) that has many potential applications ranging from
the theory of vertex algebras to the physics of SCFTs in various dimensions, to
q-series invariants in low-dimensional topology that arise, e.g. in Vafa-Witten
theory and in non-perturbative completion of complex Chern-Simons theory. In
particular, we introduce explicit numerical algorithms that efficiently
implement this bijection. This bijection is founded on preservation of
relations, a fundamental property of resurgent functions. Using resurgent
analysis we find new structures and patterns in complex Chern-Simons theory on
closed hyperbolic 3-manifolds obtained by surgeries on hyperbolic twist knots.
The Borel plane exhibits several intriguing hints of a new form of
integrability. An important role in this analysis is played by the twisted
Alexander polynomials and the adjoint Reidemeister torsion, which help us
determine the Stokes data. The method of singularity elimination enables
extraction of geometric data even for very distant Borel singularities, leading
to detailed non-perturbative information from perturbative data. We also
introduce a new double-scaling limit to probe 0-surgeries from the limiting
behavior of 1/r surgeries, and apply it to the family of
hyperbolic twist knots.Comment: 115 pages; 32 figure
A stacking-fault based microscopic model for platelets in diamond
We propose a new microscopic model for the planar defects in
diamond commonly called platelets. This model is based on the formation of a
metastable stacking fault, which can occur because of the ability of carbon to
stabilize in different bonding configurations. In our model the core of the
planar defect is basically a double layer of three-fold coordinated
carbon atoms embedded in the common diamond structure. The properties of
the model were determined using {\it ab initio} total energy calculations. All
significant experimental signatures attributed to the platelets, namely, the
lattice displacement along the direction, the asymmetry between the
and the directions, the infrared absorption peak
, and broad luminescence lines that indicate the introduction of
levels in the band gap, are naturally accounted for in our model. The model is
also very appealing from the point of view of kinetics, since naturally
occurring shearing processes will lead to the formation of the metastable
fault.Comment: 5 pages, 4 figures. Submitted for publication on August 2nd, 200
Calculation of the Phase Behavior of Lipids
The self-assembly of monoacyl lipids in solution is studied employing a model
in which the lipid's hydrocarbon tail is described within the Rotational
Isomeric State framework and is attached to a simple hydrophilic head.
Mean-field theory is employed, and the necessary partition function of a single
lipid is obtained via a partial enumeration over a large sample of molecular
conformations. The influence of the lipid architecture on the transition
between the lamellar and inverted-hexagonal phases is calculated, and
qualitative agreement with experiment is found.Comment: to appear in Phys.Rev.
Cortical Bone Viscoelasticity has Diminishing Effects on Contact Pressure in Press-Fit Stems but Does Not Jeopardize Implant Stability
Weak lensing analysis of RXC J2248.7-4431
We present a weak lensing analysis of the cluster of galaxies RXC
J2248.7-4431, a massive system at z=0.3475 with prominent strong lensing
features covered by the HST/CLASH survey (Postman et al. 2012). Based on UBVRIZ
imaging from the WFI camera at the MPG/ESO-2.2m telescope, we measure
photometric redshifts and shapes of background galaxies. The cluster is
detected as a mass peak at 5sigma significance. Its density can be parametrised
as an NFW profile (Navarro et al. 1996) with two free parameters, the mass
M_200m=(33.1+9.6-6.8)x10^14Msol and concentration c_200m=2.6+1.5-1.0. We
discover a second cluster inside the field of view at a photometric redshift of
z~0.6, with an NFW mass of M_200m=(4.0+3.7-2.6)x10^14Msol.Comment: 15 pages, 17 figures; matching published versio
Resonance ionization of sputtered atoms-progress toward a quantitative technique
The combination of RIMS and ion sputtering has been heralded as the ideal means of quantitatively probing the surface of a solid. While several laboratories have demonstrated the extreme sensitivity of combining RIMS with sputtering, less effort has been devoted to the question of accuracy. Using the SARISA instrument developed at Argonne National Laboratory, a number of well-characterized metallic
samples have been analyzed. Results from these determinations have been compared with data obtained by several other analytical methods. One significant finding is that impurity measurements down to ppb levels in metal matrices can be made quantitative by employing polycrystalline metal foils as calibration standards. This discovery substantially reduces the effort required for quantitative analysis since a single standard can be used for determining concentrations spanning nine orders of magnitude
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