Spring/Summer 2010 seminars
Department of Physics

17th June, 15:00 - Room 204

GIACOMO OLIVIERO DOVIER
SUSY neutral Higgs boson production in association with a bottom quark at the LHC

The production cross section of a neutral Higgs boson in association with a bottom quark in the MSSM is enhanced in a high tan beta scenario. This makes the process a possible candidate for the
identification of a supersymmetric Higgs particle at the LHC. The one loop electroweak corrections to the cross section can be relevant and must be taken into account.

10th June, 15:00 - Room 204

NAHID GHADERI
Adsorption of functional groups on perfect and defective graphene

Oxygen-containing functional groups can be present intentionally or unintentionally in considerable amount at graphene surface and edges. The physical properties and chemical reactivity of graphene can be affected by the presence of oxygen-containing functional groups and other molecules.
Controlling the environment could change intentionally the population of each functional group and open a way to engineer such properties. We focus here in particular on hydroxyl functional groups on perfect and defected graphene and we characterize the binding mechanism in different adsorption configurations, discussing also magnetic and electronic properties.
We found that the hydroxyl functional group weakly adsorbs individually on perfect graphene, whereas the interaction with the surface is stronger in case of adsorption of pairs or triplets or larger structures, or in case of defective graphene sheets. At high coverage hydroxyl functional groups react with each other and water formation, together with epoxy groups, can be achieved with a rather low barrier. We discuss also the case of dissociative adsorption on vacancies.

3rd June, 15:00 - Euler Room

MARIA PERESSI
Materials for spintronics

Spintronics (spin transport electronics or spin-based electronics) concerns the study of control and manipulation of spin degrees of freedom in solid-state systems. Combining standard microelectronics
with spin-dependent effects that arise from the interaction between spin of the carrier and the magnetic properties of the material offers new possibilities. After a review of basic concepts and possible applications, we will focus our attention on some examples of materials for spintronics, such as diluted magnetic semiconductors and half metals, which can be conveniently interfaced with the traditional well assessed semiconductor technology.

13th May, 15:00 - Room 204

ANTONELLO SCARDICCHIO
Typical case complexity in QSAT formulas and the most constraining classical SAT formulas

Quantum Satisfiability (QSAT) is a decision problem introduced by S. Bravyi in 2006 which is believed to be difficult for a quantum computer. I will present some results on the statistics of random quantum formulas, show the presence of two phase transitions (one SAT-UNSAT and one difficult-easy) and present an interesting connection between this problem and that of finding the most constraining classical satisfiability formulas on random graphs.

6th May, 15:00 - Room 204

CLAUDIO VERZEGNASSI
Standard and not Standard Matter searches at LHC: the role of the third quark family

The main virtues of various processes of top production at LHC as a source of fundamental tests of the Standard Model are quickly reviewed. Under the assumption of a Minimal Supersymmetric explanation of the Universe Dark Matter presence, associated top and associated bottom production would provide a clean test of the assumed properties of the extended Higgs sector of the theoretical supersymmetric description.

15nd April, 15:00 - Luigi Stasi Seminar Room

MATTEO MARSILI
Behavioral rule epidemics and financial crises

Large scale changes in the structure of the economy or financial markets, such as the current economic crisis, have their origin in the behavioral rules which agents follow. In some cases, rules have a self-reinforcing effect: the more agents adopt a rule, the more it becomes reasonable for others to accept it. This promotes such rules to social norms. Example include trusting counter-parties in financial transactions, not performing independent risk analysis and over-reliance on credit rating.
However, as rules develop and spread, becoming the norm, they may have consequences at the aggregate level which are not anticipated by the individuals. In particular, the conditions under which rules self-reinforce may gradually erode, thus provoking sharp transitions whereby most agents suddenly change their behavior. I will argue that the liquidity crisis in credit derivative markets and in the interbank market can indeed be traced back to these effects. This provides hints
on policy measures and on the regulation of financial markets.

1st April, 15:00 - Room 204

SANDRO DONADI
Spontaneous emission of radiation in dynamical reduction models

Dynamical reduction models were developed in the last decades in order to solve the measurement problem of quantum mechanics. According to these models, the temporal evolution of the state vector differs from that given by standard quantum mechanics. Hence these models give different predictions. The easiest way to test them seems to be the analysis of the spontaneous emission of electromagnetic radiation from a charged particle. In this seminar we discuss the emission rate, for the simple case of the free particle, correcting previous calculations. This analysis is the starting point for the study on more realistic systems, such as atoms.

25th March, 15:00 - Room 204

UGO MARZOLINO
Reconstruction of Master Equation Parameters trought symplectic tomography

In open quantum systems, phenomenological master equations with unknown parameters are often introduced. Here we propose procedures based on quantum tomography to reconstruct the potentially unknown parameters of a wide class of Markovian and non-Markovian master equations. According to our scheme, the system under investigation is initially prepared in a Gaussian state. At an arbitrary time t, in order to retrieve the unknown coefficients one needs to measure only a finite number of points along tomograms. Due to the limited amount of measurements required, we expect our proposal to be especially suitable for experimental implementations.

18th March, 14:30 - Luigi Stasi Seminar Room

GIANCARLO GHIRARDI
Can the reduction process peacefully coexist with special relativity?

ravis Norsen has recently reconsidered Bell’s position concerning the relativistic requirements to be imposed to the reduction process and has criticized Jarrett’s ideas concerning this matter, ideas which derive from his proof that Bell’s locality condition requires two logically independent assumptions. We will show that, in spite of the remarkable lucidity of Norsen’s arguments and of the fact that some of Jarrett’s claims are actually inappropriate, the whole problem deserves to be better focused and critically reconsidered in view of its relevance for the elaboration of a relativistic theory inducing reductions. In particular, contrary to Norsen's opinion, we will stres the conceptual relevance of distingushing the two locality request whose conjunction is equivalent to Bell’s locality.

In the second part of the talk, with reference to a specific entangled system, we will make fully evident the unavoidable contextual nature of claims concerning space-like separated events and we will take this opportunity to stress that the conclusion that quantum nonlocality implies a spooky action at a distance is not fully appropriate.

11th March, 15:00 - Room 204

MICHELE RIZZI
Adsorption and Hydrogen-Assisted Transformation of CO2 on Nickel

The nanoscale description of the reaction pathways and of the role of the intermediate species involved in a chemical process is a crucial milestone for tailoring more active, stable, and cheaper catalysts, thus providing “reaction engineering” capabilities. This level of insight has not been achieved yet for the catalytic hydrogenation of CO2 on Ni catalysts, a reaction of enormous environmental relevance. We present a thorough atomic-scale description of the mechanisms of this reaction, studied under controlled conditions on a model Ni catalyst. Results on experimental and simulated STM imaging of CO2 on Ni are also presented.

4th March, 15:00 - Room 204

GIORGIO PASTORE
Patchy colloids and Janus particles

Recent advances in synthesis of colloidal particles open the possibility of a fine control over the three-dimensional organization of materials by exploiting complex self-assembly properties in the liquid state. I'll start from such new exciting developments to review some recent results and open problems on the side of theory and simulation of simple anisotropic models. In particular, I will provide an introduction to recent work on patchy square-well models, including a patchy version of Janus particles and two patches sistems.