1,573 research outputs found
Arguments for a "U.S. Kamioka": SNOLab and its Implications for North American Underground Science Planning
We argue for a cost-effective, long-term North American underground science
strategy based on partnership with Canada and initial construction of a modest
U.S. Stage I laboratory designed to complement SNOLab. We show, by reviewing
the requirements of detectors now in the R&D phase, that SNOLab and a properly
designed U.S. Stage I facility would be capable of meeting the needs of North
America's next wave of underground experiments. We discuss one opportunity for
creating a Stage I laboratory, the Pioneer tunnel in Washington State, a site
that could be developed to provide dedicated, clean, horizontal access. This
unused tunnel, part of the deepest (1040 m) tunnel system in the U.S., would
allow the U.S. to establish, at low risk and low cost, a laboratory at a depth
(2.12 km.w.e., or kilometers of water equivalent) quite similar to that of the
Japanese laboratory Kamioka (2.04 km.w.e.). We describe studies of cosmic ray
attenuation important to properly locating such a laboratory, and the tunnel
improvements that would be required to produce an optimal Stage I facility. We
also discuss possibilities for far-future Stage II (3.62 km.w.e.) and Stage III
(5.00 km.w.e.) developments at the Pioneer tunnel, should future North American
needs for deep space exceed that available at SNOLab.Comment: 23 pages, 10 figures; revised version includes discusion about
neutrino-factory magic baseline
Stability of the Scalar Potential and Symmetry Breaking in the Economical 3-3-1 Model
A detailed study of the criteria for stability of the scalar potential and
the proper electroweak symmetry breaking pattern in the economical 3-3-1 model,
is presented. For the analysis we use, and improve, a method previously
developed to study the scalar potential in the two-Higgs-doublet extension of
the standard model. A new theorem related to the stability of the potential is
stated. As a consequence of this study, the consistency of the economical 3-3-1
model emerges.Comment: to be published in EPJ C, 13 page
Transport properties of ybco thin films near the critical state with no applied field
Transport measurements carried out on twinned ybco films are compared to the
predictions of a previously proposed model suggesting that the vortices move
along the films twin boundaries that behave as rows of Josephson weak links
[P.Bernstein and J.F.Hamet, J.Appl.Phys.95 (2004) 2569]. The obtained results
suggest that, except if the films are very thin, the twin boundaries consist of
superimposed rows of weak links with mean height,ds, whose mean length along
the TBs is an universal function of T/Tc, the reduced temperature. This
conclusion yields a general expression for the critical surface current density
of the films as a function of T/Tc and of the number of superimposed weak links
rows, while the critical current density depends on ds. A comparison of the
measurements reported by various authors shows that the nature of the substrate
and the growth technique have both a strong effect on ds . The existence of
superimposed weak links rows is attributed to extended defects generated by
y2o3 inclusions.Comment: 33 pages, 13 figures; accepted for publication in Physica
Facility for studying the effects of elevated carbon dioxide concentration and increased temperature on crops
The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO2 and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime CO2 concentrations of 363 and 692 cm3 m-3 for targets of 350 and 700 cm3 m-3 respectively. Temperatures were set to follow outside ambient or outside ambient +4-degrees-C, and hourly means were within 0.5-degrees-C of the target for 92% of the time for target temperatures greater than 6-degrees-C. Total photosynthetically active radiation incident on the crop (solar radiation supplemented by artifical light with natural photoperiod) was 2% greater than the total measured outside over the same period
Fluctuations and Instabilities of Ferromagnetic Domain Wall pairs in an External Magnetic Field
Soliton excitations and their stability in anisotropic quasi-1D ferromagnets
are analyzed analytically. In the presence of an external magnetic field, the
lowest lying topological excitations are shown to be either soliton-soliton or
soliton-antisoliton pairs. In ferromagnetic samples of macro- or mesoscopic
size, these configurations correspond to twisted or untwisted pairs of Bloch
walls. It is shown that the fluctuations around these configurations are
governed by the same set of operators. The soliton-antisoliton pair has exactly
one unstable mode and thus represents a critical nucleus for thermally
activated magnetization reversal in effectively one-dimensional systems. The
soliton-soliton pair is stable for small external fields but becomes unstable
for large magnetic fields. From the detailed expression of this instability
threshold and an analysis of nonlocal demagnetizing effects it is shown that
the relative chirality of domain walls can be detected experimentally in thin
ferromagnetic films. The static properties of the present model are equivalent
to those of a nonlinear sigma-model with anisotropies. In the limit of large
hard-axis anisotropy the model reduces to a double sine-Gordon model.Comment: 15 pages RevTex 3.0 (twocolumn), 9 figures available on request, to
appear in Phys Rev B, Dec (1994
Modelling Urban Housing Stocks for Building Energy Simulation using CityGML EnergyADE
Understanding the energy demand of a city’s housing stock is an important focus for local and national administrations to identify strategies for reducing carbon emissions. Building energy simulation offers a promising approach to understand energy use and test plans to improve the efficiency of residential properties. As part of this, models of the urban stock must be created that accurately reflect its size, shape and composition. However, substantial effort is required in order to generate detailed urban scenes with the appropriate level of attribution suitable for spatially explicit simulation of large areas. Furthermore, the computational complexity of microsimulation of building energy necessitates consideration of approaches that reduce this processing overhead. We present a workflow to automatically generate 2.5D urban scenes for residential building energy simulation from UK mapping datasets. We describe modelling the geometry, the assignment of energy characteristics based upon a statistical model and adopt the CityGML EnergyADE schema which forms an important new and open standard for defining energy model information at the city-scale. We then demonstrate use of the resulting urban scenes for estimating heating demand using a spatially explicit building energy microsimulation tool, called CitySim+, and evaluate the effects of an off-the-shelf geometric simplification routine to reduce simulation computational complexity
Smoking-gun signatures of little Higgs models
Little Higgs models predict new gauge bosons, fermions and scalars at the TeV
scale that stabilize the Higgs mass against quadratically divergent one-loop
radiative corrections. We categorize the many little Higgs models into two
classes based on the structure of the extended electroweak gauge group and
examine the experimental signatures that identify the little Higgs mechanism in
addition to those that identify the particular little Higgs model. We find that
by examining the properties of the new heavy fermion(s) at the LHC, one can
distinguish the structure of the top quark mass generation mechanism and test
the little Higgs mechanism in the top sector. Similarly, by studying the
couplings of the new gauge bosons to the light Higgs boson and to the Standard
Model fermions, one can confirm the little Higgs mechanism and determine the
structure of the extended electroweak gauge group.Comment: 59 pages, 10 figures. v2: refs added, typos fixed, JHEP versio
Simulating (electro)hydrodynamic effects in colloidal dispersions: smoothed profile method
Previously, we have proposed a direct simulation scheme for colloidal
dispersions in a Newtonian solvent [Phys.Rev.E 71,036707 (2005)]. An improved
formulation called the ``Smoothed Profile (SP) method'' is presented here in
which simultaneous time-marching is used for the host fluid and colloids. The
SP method is a direct numerical simulation of particulate flows and provides a
coupling scheme between the continuum fluid dynamics and rigid-body dynamics
through utilization of a smoothed profile for the colloidal particles.
Moreover, the improved formulation includes an extension to incorporate
multi-component fluids, allowing systems such as charged colloids in
electrolyte solutions to be studied. The dynamics of the colloidal dispersions
are solved with the same computational cost as required for solving
non-particulate flows. Numerical results which assess the hydrodynamic
interactions of colloidal dispersions are presented to validate the SP method.
The SP method is not restricted to particular constitutive models of the host
fluids and can hence be applied to colloidal dispersions in complex fluids
Spontaneous CP Violating Phase as The CKM Matrix Phase
We propose that the CP violating phase in the CKM mixing matrix is identical
to the CP phases responsible for the spontaneous CP violation in the Higgs
potential. A specific multi-Higgs model with Peccei-Quinn (PQ) symmetry is
constructed to realize this idea. The CP violating phase does not vanish when
all Higgs masses become large. There are flavor changing neutral current (FCNC)
interactions mediated by neutral Higgs bosons at the tree level. However,
unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms
of the quark masses and CKM mixing angles. Implications for meson-anti-meson
mixing, including recent data on mixing, and neutron electric dipole
moment (EDM) are studied. We find that the neutral Higgs boson masses can be at
the order of one hundred GeV. The neutron EDM can be close to the present
experimental upper bound.Comment: 16 pages, RevTex. Several typos corrected, and one reference adde
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