13,716 research outputs found
Quark Mixing Matrix Studies and Lepton Flavor Violation Searches Using Rare Decays of Kaons
I review recent results from experiments on rare decays of kaons,
concentrating on searches for lepton flavor violation (LFV) and on measurements
of quark mixing (CKM) matrix elements. The LFV results are the culmination of
15 years of experimentation at Brookhaven National Laboratory and are unlikely
to be improved upon soon. The CKM studies derive from measurements of decay
rates of charged and neutral kaons into lepton anti-lepton pairs, both with and
without a charged or neutral pion. I discuss recent results and prospects for
improved measurements that could provide an unambiguous test of the Standard
Model explanation for CP violation. This paper is the written version of a talk
presented at the Lepton-Photon Conference in August 1999.Comment: Written version of a talk at the 1999 Lepton Photon Conferenc
Quantum anisotropic Heisenberg chains with superlattice structure: a DMRG study
Using the density matrix renormalization group technique, we study spin
superlattices composed of a repeated pattern of two spin-1/2 XXZ chains with
different anisotropy parameters. The magnetization curve can exhibit two
plateaus, a non trivial plateau with the magnetization value given by the
relative sizes of the sub-chains and another trivial plateau with zero
magnetization. We find good agreement of the value and the width of the
plateaus with the analytical results obtained previously. In the gapless
regions away from the plateaus, we compare the finite-size spin gap with the
predictions based on bosonization and find reasonable agreement. These results
confirm the validity of the Tomonaga-Luttinger liquid superlattice description
of these systems.Comment: 6 pages, 6 figure
A 3D Printed Toolbox for Opto-Mechanical Components
Nowadays is very common to find headlines in the media where it is stated
that 3D printing is a technology called to change our lives in the near future.
For many authors, we are living in times of a third industrial revolution.
Howerver, we are currently in a stage of development where the use of 3D
printing is advantageous over other manufacturing technologies only in rare
scenarios. Fortunately, scientific research is one of them. Here we present the
development of a set of opto-mechanical components that can be built easily
using a 3D printer based on Fused Filament Fabrication (FFF) and parts that can
be found on any hardware store. The components of the set presented here are
highly customizable, low-cost, require a short time to be fabricated and offer
a performance that compares favorably with respect to low-end commercial
alternatives.Comment: 9 pages, 9 figure
Inevitability of Plate Tectonics on Super-Earths
The recent discovery of super-Earths (masses less or equal to 10
earth-masses) has initiated a discussion about conditions for habitable worlds.
Among these is the mode of convection, which influences a planet's thermal
evolution and surface conditions. On Earth, plate tectonics has been proposed
as a necessary condition for life. Here we show, that super-Earths will also
have plate tectonics. We demonstrate that as planetary mass increases, the
shear stress available to overcome resistance to plate motion increases while
the plate thickness decreases, thereby enhancing plate weakness. These effects
contribute favorably to the subduction of the lithosphere, an essential
component of plate tectonics. Moreover, uncertainties in achieving plate
tectonics in the one earth-mass regime disappear as mass increases:
super-Earths, even if dry, will exhibit plate tectonic behaviour.Comment: 13 pages, 2 figures and 1 table; in press in ApJ
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