RACAH Institute of Physics

Seminars

Joint High Energy Physics Seminar
Lecturer:	Prof. Joerg Teschner, University of Berlin
Subject:	On open-closed duality in \hat{c}=1 string theory
Date:	Tuesday, April 5
Time:	11:00
Place:	Neve Shalom

Astrophysics Lunch Seminar
Lecturer:	Ms. Joanna Woo, Racah Institute of Physics, Hebrew University
Subject:	Near-Field Cosmology with Dwarf Elliptical Galaxies (Summary of a recent IAU colloquium) IAUC #198
Date:	Tuesday, April 5
Time:	12:30
Place:	Kaplun 200

Physics Colloquium
Lecturer:	Prof. Nathan Paldor, Dept. of Atmospheric Sciences, Institute of Earth Sciences, Hebrew University of Jerusalem
Subject:	A Schrödinger equation formulation of waves at the ocean's surface and recent Topex/Poseidon observations
Date:	Tuesday, April 5
Time:	16:00
Place:	Levin 8

Nonlinear Physics Seminar
Lecturer:	Prof. Ehud Meron, Ben Gurion University
Subject:	Ecosystem Engineers: From Pattern Formation to Habitat Creation
Date:	Wednesday, April 6
Time:	14:00
Place:	Danciger 10

Abstract
Habitat and species richness in drylands are affected by the dynamics of a few key species, termed ecosystem engineers. These species modulate the landscape and redistribute the water resources so as to allow the introduction of other species. A mathematical model is developed for a pair of ecosystem engineers commonly found in drylands: plants forming vegetation patterns and cyanobacteria forming soil crusts. The model highlights conditions for habitat creation and for habitat richness, and suggests a novel mechanism for species richness change in response to climatic fluctuations or human disturbances.

Solid State Seminar
Lecturer:	Dr. Aviad Frydman, Bar Ilan University
Subject:	Voltage-dependent magneto-transport through magnetic nanoparticles
Date:	Thursday, April 7
Time:	12:00
Place:	Danciger 10

Abstract
The electric transport through systems of ferromagnetic grains is found to depend non-trivially on the applied voltage. In this talk, two examples for unique voltage-dependent magneto-transport phenomena will be presented. The first is an asymmetric magnetoresistance [R(H) \neq R(-H)] observed in small ferromagnetic dots weakly connected to leads. The effect, (of up to ~12%) is maximal for samples having resistance of a few kOhms and it disappears for samples well into the metallic or insulating phases. Varying the bias voltage, V, affects the asymmetry considerably, and, in many cases leads to a change of sign. The second effect is a voltage-dependent magnetic coercivity observed in granular ferromagnets. The coercive field, Hc, varies non-monotonically with voltage, exhibiting a peak for intermediate V. We discuss these observations and contemplate on the effect of non-equilibrium transport on the magnetic properties of nano-magnets.