Economics of grain-fallow rotations in Saskatchewan

Non-Peer Reviewe

A Minimal Inflation Scenario

We elaborate on a minimal inflation scenario based entirely on the general properties of supersymmetry breaking in supergravity models. We identify the inflaton as the scalar component of the Goldstino superfield. We write plausible candidates for the effective action describing this chiral superfield. In particular the theory depends (apart from parameters of O(1)) on a single free parameter: the scale of supersymmetry breaking. This can be fixed using the amplitude of CMB cosmological perturbations and we therefore obtain the scale of supersymmetry breaking to be 10^{12-14} GeV. The model also incorporates explicit R-symmetry breaking in order to satisfy the slow roll conditions. In our model the eta-problem is solved without extra fine-tuning. We try to obtain as much information as possible in a model independent way using general symmetry properties of the theory's effective action, this leads to a new proposal on how to exit the inflationary phase and reheat the Universe.Comment: matches published version (typo corrected

Current Distribution in the Three-Dimensional Random Resistor Network at the Percolation Threshold

We study the multifractal properties of the current distribution of the three-dimensional random resistor network at the percolation threshold. For lattices ranging in size from $8^3$ to $80^3$ we measure the second, fourth and sixth moments of the current distribution, finding {\it e.g.\/} that $t/\nu=2.282(5)$ where $t$ is the conductivity exponent and $\nu$ is the correlation length exponent.Comment: 10 pages, latex, 8 figures in separate uuencoded fil

Electronic transport through domain walls in ferromagnetic nanowires: Co-existence of adiabatic and non-adiabatic spin dynamics

We study the effect of a domain wall on the electronic transport in ferromagnetic quantum wires. Due to the transverse confinement, conduction channels arise. In the presence of a domain wall, spin up and spin down electrons in these channels become coupled. For very short domain walls or at high longitudinal kinetic energy, this coupling is weak, leads to very few spin flips, and a perturbative treatment is possible. For very long domain wall structures, the spin follows adiabatically the local magnetization orientation, suppressing the effect of the domain wall on the total transmission, but reversing the spin of the electrons. In the intermediate regime, we numerically investigate the spin-dependent transport behavior for different shapes of the domain wall. We find that the knowledge of the precise shape of the domain wall is not crucial for determining the qualitative behavior. For parameters appropriate for experiments, electrons with low longitudinal energy are transmitted adiabatically while the electrons at high longitudinal energy are essentially unaffected by the domain wall. Taking this co-existence of different regimes into account is important for the understanding of recent experiments.Comment: 10 pages, 6 figure

Destruction of diagonal and off-diagonal long range order by disorder in two-dimensional hard core boson systems

We use quantum Monte Carlo simulations to study the effect of disorder, in the form of a disordered chemical potential, on the phase diagram of the hard core bosonic Hubbard model in two dimensions. We find numerical evidence that in two dimensions, no matter how weak the disorder, it will always destroy the long range density wave order (checkerboard solid) present at half filling and strong nearest neighbor repulsion and replace it with a bose glass phase. We study the properties of this glassy phase including the superfluid density, energy gaps and the full Green's function. We also study the possibility of other localized phases at weak nearest neighbor repulsion, i.e. Anderson localization. We find that such a phase does not truly exist: The disorder must exceed a threshold before the bosons (at weak nn repulsion) are localized. The phase diagram for hard core bosons with disorder cannot be obtained easily from the soft core phase diagram discussed in the literature.Comment: 7 pages, 10 eps figures include

Disordered Bosons: Condensate and Excitations

The disordered Bose Hubbard model is studied numerically within the Bogoliubov approximation. First, the spatially varying condensate wavefunction in the presence of disorder is found by solving a nonlinear Schrodinger equation. Using the Bogoliubov approximation to find the excitations above this condensate, we calculate the condensate fraction, superfluid density, and density of states for a two-dimensional disordered system. These results are compared with experiments done with ${}^4{\rm He}$ adsorbed in porous media.Comment: RevTeX, 26 pages and 10 postscript figures appended (Figure 9 has three separate plots, so 12 postcript files altogether

Experimental probes of emergent symmetries in the quantum Hall system

Experiments studying renormalization group flows in the quantum Hall system provide significant evidence for the existence of an emergent holomorphic modular symmetry $\Gamma_0(2)$. We briefly review this evidence and show that, for the lowest temperatures, the experimental determination of the position of the quantum critical points agrees to the parts \emph{per mille} level with the prediction from $\Gamma_0(2)$. We present evidence that experiments giving results that deviate substantially from the symmetry predictions are not cold enough to be in the quantum critical domain. We show how the modular symmetry extended by a non-holomorphic particle-hole duality leads to an extensive web of dualities related to those in plateau-insulator transitions, and we derive a formula relating dual pairs $(B,B_d)$ of magnetic field strengths across any transition. The experimental data obtained for the transition studied so far is in excellent agreement with the duality relations following from this emergent symmetry, and rule out the duality rule derived from the ``law of corresponding states". Comparing these generalized duality predictions with future experiments on other transitions should provide stringent tests of modular duality deep in the non-linear domain far from the quantum critical points.Comment: 12 pages, 9 figure

WISP genes are members of the connective tissue growth factor family that are up-regulated in Wnt-1-transformed cells and aberrantly expressed in human colon tumors

Wnt family members are critical to many developmental processes, and components of the Wnt signaling pathway have been linked to tumorigenesis in familial and sporadic colon carcinomas. Here we report the identification of two genes, WISP-1 and WISP-2, that are up-regulated in the mouse mammary epithelial cell line C57MG transformed by Wnt-1, but not by Wnt-4. Together with a third related gene, WISP-3, these proteins define a subfamily of the connective tissue growth factor family. Two distinct systems demonstrated WISP induction to be associated with the expression of Wnt-1. These included (i) C57MG cells infected with a Wnt-1 retroviral vector or expressing Wnt-1 under the control of a tetracyline repressible promoter, and (ii) Wnt-1 transgenic mice. The WISP-1 gene was localized to human chromosome 8q24.1-8q24.3. WISP-1 genomic DNA was amplified in colon cancer cell lines and in human colon tumors and its RNA overexpressed (2- to >30-fold) in 84% of the tumors examined compared with patient-matched normal mucosa. WISP-3 mapped to chromosome 6q22-6q23 and also was overexpressed (4- to >40-fold) in 63% of the colon tumors analyzed. In contrast, WISP-2 mapped to human chromosome 20q12-20q13 and its DNA was amplified, but RNA expression was reduced (2- to >30-fold) in 79% of the tumors. These results suggest that the WISP genes may be downstream of Wnt-1 signaling and that aberrant levels of WISP expression in colon cancer may play a role in colon tumorigenesis

A Survey of Containner Breeding Mosquito Species in Kuching Area

A visual larval inspection was done from October 2010 to January 2011 to identify the common species of container-breeding mosquitoes in Kuching, Sarawak. A total of 14 areas in Kuching were surveyed. All the 1216 larvae collected were identified. The dominant species was Ae. albopictus (79.03%), followed by Culex sp. (20.97%). The most common breeding sources were plastic containers. The container index was the highest for Taman Budaya, Kuching (83.33%). Larval breeding habitats were found within the temperature range of 25.1⁰C to 33.0⁰C and pH of 3.0 to 9.9. There is no significant difference of water temperature between Ae. albopictus (30.2⁰C ± 1.0) and Culex sp. (30.2⁰C ± 0.6). However, the pH of water for Culex sp. (7.6 ± 0.1) was found significantly lower than that of Ae. albopictus (7.8 ± 0.9). Mean pH of natural containers (6.7 ±1.3) was significantly lower than mean pH for artificial containers (7.8 ± 1.1). Mix breeding of Ae. albopictus and Culex sp. was found in coconut and plant saucers collected from Kampung Kudei and Waterfront, respectively. Based on its dominance and versatility, we suggest that Ae. albopictus may present as a sole vector for dengue virus in Kuching

Four-point Functions of Lowest Weight CPOs in N=4 SYM_4 in Supergravity Approximation

We show that the recently found quartic action for the scalars from the massless graviton multiplet of type IIB supergravity compactified on AdS_5\times S^5 background coincides with the relevant part of the action of the gauged N=8 5d supergravity on AdS_5. We then use this action to compute the 4-point function of the lowest weight chiral primary operators \tr(\phi^{(i}\phi^{j)}) in N=4 SYM_4 at large $N$ and at strong `t Hooft coupling.Comment: Latex, 21p, misprints are correcte