Experimental Constraints on the Neutralino-Nucleon Cross Section

In the light of recent experimental results for the direct detection of dark matter, we analyze in the framework of SUGRA the value of the neutralino-nucleon cross section. We study how this value is modified when the usual assumptions of universal soft terms and GUT scale are relaxed. In particular we consider scenarios with non-universal scalar and gaugino masses and scenarios with intermediate unification scale. We also study superstring constructions with D-branes, where a combination of the above two scenarios arises naturally. In the analysis we take into account the most recent experimental constraints, such as the lower bound on the Higgs mass, the $b\to s\gamma$ branching ratio, and the muon $g-2$.Comment: References added, bsgamma upper bound improved, results unchanged, Talk given at Corfu Summer Institute on Elementary Particle Physics, August 31-September 20, 200

N=1 Supersymmetric Yang-Mills on the lattice at strong coupling

We study N=1 supersymmetric SU(N) Yang-Mills theory on the lattice at strong coupling. Our method is based on the hopping parameter expansion in terms of random walks, resummed for any value of the Wilson parameter r in the small hopping parameter region. Results are given for the mesonic (2-gluino) and fermionic (3-gluino) propagators and spectrum.Comment: Latex file. 43 pages. Minor additional comments, references added, typos corrected. Accepted for publication in Int. J. Mod. Phys.

Quasi-stationary states and the range of pair interactions

"Quasi-stationary" states are approximately time-independent out of equilibrium states which have been observed in a variety of systems of particles interacting by long-range interactions. We investigate here the conditions of their occurrence for a generic pair interaction V(r \rightarrow \infty) \sim 1/r^a with a > 0, in d>1 dimensions. We generalize analytic calculations known for gravity in d=3 to determine the scaling parametric dependences of their relaxation rates due to two body collisions, and report extensive numerical simulations testing their validity. Our results lead to the conclusion that, for a < d-1, the existence of quasi-stationary states is ensured by the large distance behavior of the interaction alone, while for a > d-1 it is conditioned on the short distance properties of the interaction, requiring the presence of a sufficiently large soft-core in the interaction potential.Comment: 5 pages, 3 figures; final version to appear in Phys. Rev. Let

Onsager reciprocity relations without microscopic reversibility

In this paper we show that Onsager--Machlup time reversal properties of thermodynamic fluctuations and Onsager reciprocity relations for transport coefficients can hold also if the microscopic dynamics is not reversible. This result is based on the explicit construction of a class of conservative models which can be analysed rigorously.Comment: revtex, no figure

Generalized model of blockage in particulate flow limited by channel carrying capacity

We investigate stochastic models of particles entering a channel with a random time distribution. When the number of particles present in the channel exceeds a critical value $N$, a blockage occurs and the particle flux is definitively interrupted. By introducing an integral representation of the $n$ particle survival probabilities, we obtain exact expressions for the survival probability, the distribution of the number of particles that pass before failure, the instantaneous flux of exiting particle and their time correlation. We generalize previous results for $N=2$ to an arbitrary distribution of entry times and obtain new, exact solutions for $N=3$ for a Poisson distribution and partial results for $N\ge 4$.Comment: 13 pages, 9 figure

Partitioning Evapotranspiration in Forested Peatlands within the Western Boreal Plain, Fort McMurray, Alberta, Canada

Forested peatlands in the Western Boreal Plain (WBP) represent hydrologically sensitive ecosystems that often support an open-crown forest of Picea mariana and/or Larix laricina. These systems store globally significant soil carbon, containing one-fourth to one-third of the world’s soil organic carbon pool (Turunen et al., 2002),serving a critical role in regulating atmospheric CO2. Recent studies indicate that the hydrological conditions are the critical determinant of a peatland’s carbon budget (Price et al., 2005; Aurela et al., 2007).To understand current hydrological conditions, it is essential to accurately estimate the rate of ET, due to its dominance within a peatland’s water balance (Price and Maloney, 1994; Fraser et al., 2001; Lafleur, 2008). The mechanism by which peatlands retain and exchange water with the atmosphere is important to maintain the stability of these systems. However, this stability is threatened by the impacts of both warmer and drier conditions associated with climate change, and altered hydroclimatic cycles as a result of landscape disturbance. Increasing drought (frequency and severity) has the potential to increase tree growth, modifying density, size and spatial arrangement of the trees (Kettridge et al., 2013). This expansion impedes incoming solar radiation from reaching the peat surface, potentially limiting surface evapotranspiration (ET), which at present, represents the main flux water loss from these systems. A reduction in surface ET(ETsurf)could further produce a reduction in total fen ET, despite predicted increases in canopy transpiration (T) attributed to the higher stem density. This research partitions ET between the canopy and understory between two typical fens, under current climate conditions, within the oil sands region of Fort McMurray, Alberta. The effects of climate, tree canopy and surface vegetation on the energy balance and ET processes were analyzed using a micrometeorology (MET) and eddy-covariance (EC) data in two typical Western Boreal Plain (WBP) fens during the growing 2013 season. Flux data were partitioned through the application of the stem heat balance (SHB) method and dynamic closed chambers. The two fens are distinguished as a poor fen with an open canopy composed of Picea mariana, and a rich fen, with a dense Larix laricina canopy. Additionally, the two fens are distinguished by differences in localized climate, with the poor fen subjected to significantly cooler air (Ta) and soil (Tg) temperatures. The energy balance of both fens was regulated by the latent heat flux (QE). The seasonal pattern of ET was closely linked with growing season net radiation (Q*),vapour pressure deficit (VPD), Ta and precipitation (P) events, averaging 2.3 mm d-1 and 3.5 mm d-1 between the poor, open canopy fen and rich, dense canopy fen, respectively. A strong, positive linear correlation was exhibited between the control parameters Q*, Ta, and daily transpiration (T).Seasonal mean T rates varied over the four month growing season at the Picea mariana poor fen, averaging 0.3 mm d-1, while T rates at the Larix laricina rich fen supplied a higher contribution to the fen’s total ET flux, averaging 2.7 mm d-1. Both ET and T reached maxima in conditions of high Q*, Ta, and moderate to high VPD, that coincided with lower relative humidity (RH) and moderate windspeed (u). Neither ET nor T demonstrated a direct relationship with volumetric moisture content (VMC), due to the consistently high water table, generally at or above the peat surface, maintained at both sites. The poor fen’s discontinuous Picea mariana canopy permitted a larger degree of incoming radiation to reach the underlying peat surface, while the rich fen’s higher tree density composed of the Larix laricina, limited incoming radiation due to shading. Subsequently, surface vegetation of the former was dominated by Sphagnum moss, while the latter was composed of a variety of feather moss and the brown moss, Tomenthypnum nitens. The poor fen’s open canopy and dominant Sphagnum moss resulted in the dominance of the ETsurf, with a mean of 0.8 mm d-1, contributing approximately \u3e 80% to the daily ET budget. Conversely, the rich fen’s dense canopydiminished the impact of ETsurf to 0.5 mm d-1, contributing \u3c 20% to the total ET flux. Increased tree density from a Picea mariana open-canopy, to a Larix laricina dense canopy,reduced average PAR reaching the underlying surface to \u3c 500 μmolm-2 s-1 and \u3c 300 μmol m-2 s-1. Although the presence of an overstory did not produce a microclimate that was statistically different between open and covered plot conditions, it did generally support cooler, wet conditions that inhibited ETsurf

Neutral B Meson Mixing and Heavy-light Decay Constants from Quenched Lattice QCD

We present high-statistics results for neutral $B$-meson mixing and heavy-light-meson leptonic decays in the quenched approximation from tadpole-improved clover actions at $\beta = 6.0$ and $\beta = 6.2$. We consider quantities such as $B_{B_{d(s)}}$, $f_{D_{d(s)}}$, $f_{B_{d(s)}}$ and the full $\Delta B=2$ matrix elements as well as the corresponding SU(3)-breaking ratios. These quantities are important for determining the CKM matrix element $|V_{td}|$.Comment: LATTICE98(heavyqk). Revised version. Typos in the second and third equations corrected. Very small changes to text. Results unchange

Large deviation approach to non equilibrium processes in stochastic lattice gases

We present a review of recent work on the statistical mechanics of non equilibrium processes based on the analysis of large deviations properties of microscopic systems. Stochastic lattice gases are non trivial models of such phenomena and can be studied rigorously providing a source of challenging mathematical problems. In this way, some principles of wide validity have been obtained leading to interesting physical consequences.Comment: Extended version of the lectures given by G. Jona-Lasinio at the 9th Brazilian school of Probability, August 200

Quantitative analysis of Clausius inequality

In the context of driven diffusive systems, for thermodynamic transformations over a large but finite time window, we derive an expansion of the energy balance. In particular, we characterize the transformations which minimize the energy dissipation and describe the optimal correction to the quasi-static limit. Surprisingly, in the case of transformations between homogeneous equilibrium states of an ideal gas, the optimal transformation is a sequence of inhomogeneous equilibrium states.Comment: arXiv admin note: text overlap with arXiv:1404.646

Minimum dissipation principle in stationary non equilibrium states

We generalize to non equilibrium states Onsager's minimum dissipation principle. We also interpret this principle and some previous results in terms of optimal control theory. Entropy production plays the role of the cost necessary to drive the system to a prescribed macroscopic configuration