The Graduate Program in Physics at Pavia includes three main programs (curricula):
PHYSICS OF FUNDAMENTAL INTERACTIONS
CONDENSED MATTER PHYSICS
INTERDISCIPLINARY AND APPLIED PHYSICS
Formative research activities in these programs occurs in an unusually broad range of experimental and theoretical areas covering
Interdisciplinary research is fostered and encouraged, and students have the chance to work on a wide range of forefront research, both on pure and applied fields.
Student research is supervised by faculty in the Department of Physics, by affiliated faculty, and by members of the local section of the Italian Institute of Nuclear Physics (INFN). Refer to related departments and research centers in our links page : http://dottorato-fisica.pv.infn.it/ for information on faculty members pursuing research in the areas listed.
Here a detailed overview of Graduate Research carried out at Pavia
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NUCLEAR AND SUBNUCLEAR PHYSICS:
ATLAS is one of two general-purpose detectors at the LHC. It investigates a wide range of physics, including the search for the Higgs boson, the scenarios beyond the Standard Model, and particles that could be candidates for dark matter. ATLAS has recorded and will record sets of measurements on the particles created in the LHC collisions - their paths, energies, and their identities.
DREAM During the past seven years, the DREAM Collaboration has systematically investigated all factors that determine and limit the precision with which the properties of hadrons and jets can be measured in calorimeters. Using simultaneous detection of the deposited energy and the Cherenkov light produced in hadronic shower development (dual readout), the fluctuations in the electromagnetic shower fraction could be measured event by event and their effects on signal linearity, response function and energy resolution eliminated. The Italian-US Collaboration has recently started the construction of a full containment calorimeter which incorporates all these elements and shouls make possible to measure the four-momenta of both electrons, hadrons and jets with high precision, in an instrument that can be simply calibrated with electrons. (Daniela Rebuzzi)
AEGIS . Does antihydrogen fall with the same acceleration as hydrogen? The principle of universality of free fall (or weak equivalence principle, WEP) states that all bodies fall with the same acceleration, independent of mass and composition. The WEP has been tested with very high precision for matter but never for antimatter. AEgIS is an experiment by a collaboration of physicists from all around the world to test the WEP with antiprotons at the European laboratory CERN, using the antiproton decelerator (AD).
The goal of the AEgIS experiment is a first direct measurement of the earth's gravitational acceleration with the simplest form of electrically neutral antimatter, namely antihydrogen. In the first phase a measurement of the gravity force with 1% precision will be carried out by sending an antihydrogen beam lauched horizontally in a vacuum tube and by measuring the gravitational sag with a Moiré deflectometer and a position sensitive detector.
The essential steps leading to the production of antihydrogen and the measurement of g with AEgIS are the following (for details see the experimental proposal at http://aegis.web.cern.ch):
The activities of the Aegis group of the INFN unit and of the University of Pavia are connected with the data acquisition of the apparatus, with the montecarlo simulation of the detectors used to detect antihydrogen and with the data analysis of the experiment. For further information please visit the experiment website: http://aegis.web.cern.ch/aegis/ . (Andrea Fontana, Cristina Riccardi, Alberto Rotondi)
PANDA . PANDA is the acronym for antiProton ANnihilation at DArmstadt. The experiment, in preparation at the GSI laboratories in Darmstadt (Germany), will exploit the annihilation of antiprotons (on protons and nuclei) to perform high precision charmonium spectroscopy. Moreover, a wide range of topics in the nuclear physics field will be addressed, such as the study of gluonic excitations and non standard bound states, meson properties in medium modification, nuclear structure and hypernuclear physics. For further information please visit the experiment website: http://www-panda.gsi.de/. Since the detector is a high precision spectrometer, a key factor is the track reconstruction capability. The Pavia group, whose participation to the project dates back to PANDA early stages, is actively involved in the realization of the Central Tracker (Straw Tube Tracker), in collaboration with Frascati, Ferrara, Jülich, Cracow and other groups. In this project, its main role is the implementation of the software related to the tracking system. Specifically, it has the responsibility of the simulation and reconstruction code for the Straw Tube Tracker. It is also involved in the implementation of the algorithms for the track reconstruction (pattern recognition, track fitting, Kalman filter). Finally, it has the responsibility of the maintenance of the track following package (GEANE), used in the Kalman filter procedure. (G. Boca, A. Braghieri, S. Costanza, P. Genova, L. Lavezzi, P. Montagna, A. Rotondi)
MAMBO The goal of the MAMBO experiment is the study of the nucleon and nuclear structure in the non-perturbative QCD regime. This goal is achieved, at the Mainz and Bonn tagged photon facilities, with the accurate measurement of the single and multi pion photo-production processes, both on the free and bound nucleons, in the energy region from threshold to 3.5 GeV with the use of a polarized gamma-ray beam and/or polarized targets. The broad physics program that is thus accessible includes the:
The Pavia group has been actively involved in these research activities for many years, and offers a wide range of opportunities for both diploma and PhD thesis. (A. Braghieri, P. Pedroni)
Physics applied to Medicine. the INFN-CNAO challenge for treatment of eye tumors The new hadron accelerator at the CNAO (Centro Nazionale di Adroterapia Oncologica) Laboratories in Pavia allows to investigate the feasibility of a new dedicated line for the treatment of intraocular uveal melanomas by using an active proton beam scan. The active group in Pavia studies the simulation with the Geant4 tool of the CNAO setup with the passive/active components on the expected beam-line as well as the detector, a human eye with a tumour inside. The simulation tool developed can be used to study a new design of treatment elements and to evaluate validity and performance of the treatment planning systems. The idea behind is to show the possibility to adapt the CNAO standard beam line, with some optimization, for dose delivery to the human eye without any dramatic change of the present machine experimental setup. This study is also important as a prediction tool to implement new detectors (body organs, experimental water detectors), active/passive beam setup components and to evaluate the dose received on the target and its three dimensional geometrical distribution. Patient treatment plans are also studied and analyzed (Adele Rimoldi).
THEORETICAL AND MATHEMATICAL PHYSICS:
Quantum Gravity and Quantum Field Theory
Among the many significant ideas and developments that connect Mathematics with contemporary Physics one of the most intriguing is the role that Quantum Field Theory (QFT) plays in Geometry and Topology. We can argue back and forth on the relevance of such a role, but the perspective QFT offers is often surprising and far reaching. Examples abound, and a fine selection is provided by the revealing insights offered by Yang--Mills theory into the topology of 4-manifolds, by the relation between Knot Theory and topological QFT, and most recently by the interaction between Strings, Riemann moduli space, and enumerative geometry. These techniques afford a geometrical perspective which is always quite non--trivial and extremely rich. It is within such a Quantum Geometry framework that our group (M. Carfora, A. Marzuoli, C. Dappiaggi) investigates aspects of the relation between an important class of QFTs, General Relativity, Cosmology, and Quantum Gravity. Specific research themes that we address and which offer a wide range of possibilities for PhD thesis are: Quantum Field Theory on curved spacetimes; Ricci flow and Quantum Field Theory Landscaping; Two-dimensional Quantum Gravity, String Dualities, and the geometry of Riemann Moduli Space theory; Topology of manifolds and Topological Quantum Field Theory; Combinatorial Framework for Topological Quantum Computing. (Mauro Carfora)
Hadronic structure and QCD: theory and phenomenology
Our goal is to explore and understand the internal structure of nucleons in terms of their elementary constituents, i.e., quarks and gluons. Our research activity aims at answering fundamental questions such as: Can we define a "shape" of the nucleon and how does it look like? What generates the spin of the nucleon? In principle, the structure of the nucleon should be computed starting from the theory of Quantum Chromodynamics (QCD). In practice, the confinement of quarks and gluons within nucleons is a nonperturbative phenomenon, and QCD is extremely hard to solve in nonperturbative regimes. For this reason, despite the enormous progress of the last decades, we still have a limited knowledge of the internal structure of nucleons, which constitute more than 99% of ordinary matter. We turn to experimental measurements to gather the largest amount of information concerning nucleon structure. We make use of the tools of perturbative QCD to study hard scattering processes such as Deep Inelastic Scattering. We try to interpret the experimental measurements in terms of quark and gluon distribution functions. We compute the relevant quantities using models that effectively replace nonperturbative QCD. We make predictions for unmeasured observables. We actively participate in suggesting and planning future experimental measurements. Specific research themes that our group (A. Bacchetta, M. Guagnelli, B. Pasquini, M. Radici) addresses and that offer a wide range of possibilities for PhD thesis are: phenomenological and formal studies of transverse-momentum dependent parton distributions and generalized parton distributions; modeling parton distributions; study of the spin structure of the proton. (A. Bacchetta, M. Guagnelli, B. Pasquini, M. Radici)
Nuclear theory: electroweak reactions and stable and exotic nuclei.
In spite of many decades of successful studies, the structure of nuclei is not yet completely understood. Sophisticated mean field theories have produced a wealth of data, but have also shown up their limits. The role of correlations in nuclei is larger than expected. The short range correlations, which are due to the short-range repulsion of the nucleon-nucleon interaction, have been deeply investigated, thanks to the use of realistic forces including many-body contributions, but it was found that large effects are also given by tensor correlations, which are due to the tensor component of the nuclear interaction, and to long-range correlations, which are due to the coupling between the single-particle dynamics and the collective excitation modes of the nucleus. Electron scattering reactions appear a preferential tool to investigate nuclear properties, in particular, but not only, single-particle ones. Inclusive and exclusive quasi-elastic electron scattering and electron-induced reactions with direct one- and two-nucleon emission have been widely investigated in Pavia. Neutrino interactions can be used in a similar way and, notwithstanding their very small cross sections, have the advantage of being sensitive to parity non conserving components of the nuclear current. Moreover, neutrinos are important for astrophysical studies, as their small interaction makes it possible to investigate the inner properties of stars. As their detection implies finite nuclei, it is essential to know with high precision the mechanism of their interaction with nuclei and the related cross sections. Exotic nuclei, which are nuclei with neutron or proton excess, are also important in astrophysics, as they can have a sensible effect in the process of nucleosynthesis. Moreover, they can give insight into the evolution of nuclear properties when the neutron-proton asymmetry increases. New phenomena are expected, in particular with respect to the shell model.
Our group (C. Giusti, F.D. Pacati, A. Meucci) has been involved for many years in collaborations with international laboratories to explain the experimental data and to predict the order of magnitude of the quantities to be measured in new experiments. We are also actively involved in national and international collaborations with theoretical groups for the comparison of different models and the development of new and more refined models for the analysis of data from electron and neutrino scattering experiments.
Specific research themes that our group addresses and that offer a wide range of possibilities for PhD theses: nuclear reactions with electroweak probes, relativistic models for quasi-elastic electron and neutrino-nucleus scattering, electron-induced reactions on exotic nuclei, relativistic mean field models. (C. Giusti)
Theoretical physics of elementary particles
With the announcement of the observation of a Higgs-like particle at the CERN LHC, particle physics entered a new era. The next endeavour demands to probe the fundamental properties of the newly discovered boson, such as its spin and parity, its couplings to the different fermions and gauge bosons and its self-coupling. It will be also important to establish whether the newly found boson is a fundamental or a composite particle, and whether this discovery is just the coronation of the Standard Model or a milestone along a path yet largely unexplored. To this end, it will be crucial to pursue the search for new particles beyond the spectrum of the Standard Model in the next years to come, as well as to perform precision measurements of the production processes and decays of the Higgs-like particle. This research is expected to take place at the energy and intensity frontiers and is strictly tight to the cosmic frontier, since from collider experiments it will be possible to infer the existence - and possibly to discover – candidate particles able to solve the problem of the origin of the dark matter in the universe. The activity of the high energy theory group falls in the above general framework.
The team (G. Montagna, O. Nicrosini and F. Piccinini) has been actively involved for many years in the development of precision calculations and Monte Carlo generators for physics studies at the colliders at energy and intensity frontiers.
Theoretical research is carried out in view of the analysis of real collider data, both at the hadron colliders Tevatron and LHC and at electron-positron colliders at the GeV scale (flavor factories). Specific research themes that are currently addressed and offer a wide range of possibilities for a PhD thesis are: electroweak and QCD physics at the LHC, study of the properties of the Higgs boson and nature of the mechanism of electroweak symmetry breaking, higher-order calculations for tests of the Standard Model and searches for new physics at hadron colliders and flavor factories (G. Montagna, O. Nicrosini and F. Piccinini).
CONDENSED MATTER, OPTICAL PHYSICS, QUANTUM INFORMATION:
PHOTONICS AND NANOSTRUCTURES
The Photonics and Nanostructures research group evolves from solid state physics and optical properties of materials, to recent advances in optical investigations of materials with micrometric and sub-micrometric structures – the area that is broadly called nanophotonics and plasmonics. The Optical Spectroscopy Laboratory is equipped with a number of different techniques on a broad spectral range (from far infrared to vacuum ultraviolet): beyond the most common experiments based on reflectance, absorbance, photoluminescence, ellipsometry, dedicated set-ups have been implemented, both spatially and temporally resolved, to perform linear and nonlinear photonics and plasmonics studies (G. Guizzetti, F. Marabelli, M. Patrini, M. Galli, D. Bajoni). Theoretical research is developed both in support to experimental activities, and for basic investigations of radiation-matter interaction and nanophotonic systems (L.C. Andreani, D. Gerace, M. Liscidini, see also Quantum Photonics section). The group activities are presently focussed on three main research topics:
a. The electronic structure and the optical response of semiconductors, especially III-V compounds, Silicon, and metals, in bulk materials and heterostructures, as thin films, wires, dots. More recently, an activity on polymeric and conjugate polymeric semiconductors has started, with emphasis on optical response and photophysics of excited states. Applications of these materials (both semiconductors and polymers) are especially in the fields of microelectronics, optoelectronics, and photovoltaics beyond other material-science issues.
b. The experimental investigation of photonic crystals, i.e. systems with a periodic dielectric function in one, two, or three dimensions. Such systems are particularly interesting for a great variety of physical phenomena and they are promising for applications to optoelectronics and optical communication, lasers, integrated photonics and photovoltaic energy conversion. The investigated structures include photonic crystal waveguides and nanocavities in Silicon, SOI and III-V semiconductors for the control of light propagation, enhanced light emission, and quantum photonics experiments, but also 3D structures like direct and inverse opals.
c. Plasmonic or hybrid photonic systems, with applications in the development of photonic biosensors, and plasmonic surfaces for chemical and biochemical interactions. Two different systems have been proposed: i) dielectric multilayers supporting Bloch surface waves; ii) metallic nanostructures supporting surface plasmons polaritons, both propagating and localized. In both cases the e.m. field confinement and amplification allow the detection at high sensitivity in the far-field of biomolecular species chemically bound or adsorbed on the active area of the biosensor. Optical detection is feasible via surface Plasmon resonances (SPR), fluorescence, surface Raman scattering, or light diffraction signals. (M. Patrini)
From the theoretical side, the group of Photonics and Nanostructures has been dealing with a number of problems related to the optical properties, and radiation-matter interaction effects in complex photonic and plasmonic nanostructures, such as photonic crystals, waveguides, nanocavities (L.C. Andreani, D. Gerace, M. Liscidini).
Semiclassical and quantum descriptions of radiation-matter interaction are also a subject of considerable interest within the group. Here the concept of photon confinement in low-dimensional dielectric lattices is linked to the analogous concept of electron confinement in semiconductor nanostructures. Our current activities are still focused on theoretical descriptions photonic and electronic nanostructures, with the aid of models as well as various numerical approaches. For more information, please visit the link to the webpage nanophotonics.
Quantum photonics is an emerging field of nanoscale nonlinear optics, with the aim of studying and exploiting nonlinear optical properties in the extreme quantum limit, ultimately down to the single-photon level. We are interested in single-photon nonlinear optics in photonic nanostructures. Our interest is currently twofold: on one hand we are investigating the fundamental aspects of strongly correlated photonic systems, where the similarities of strongly coupled nonlinear cavities with strongly correlated electronic systems is a constant source of inspiration for the emergence of new physical phenomena; on the other, controlling single photons with single photons might provide prospective nanoscale devices, such as single-photon transistors or switches (D. Gerace)
Quantum Information and QFT
The Group QUIT (Quantum Information Theory Group) has worked in the field of Quantum information since the very beginning of the discipline, with main focus on designing new quantum measurements and transformations. QUIT pioneered the technique of quantum tomography of states and transformations, introduced the new notion of "quantum comb" for optimizing quantum algorithms and quantum protocols, studied security of quantum cryptographic protocols, found numerous new types of optimal measurements and transformations. In the last ten years QUIT members used their experience in addressing foundations of quantum theory (QT), and, more recently, of quantum field theory (QFT). In 2011 A long PRA has been published where three authors of QUIT derived QT from six information theoretical axioms, work that got a viewpoint on Physics, and has been the object of sessions of international conferences. The new axiomatization lead to a new powerful diagrammatic framework for deriving general theorems, without using the mathematical representation of QT. Other groups internationally are currently involved in the new axiomatization program pioneered by QUIT, and the program has lead to new possibilities of proving statements about causality, nonlocality, hidden-variable representations, completeness, complementarity and similar issues for general probabilistic theories. This new angle for looking at QT "from outside" is leading to new powerful insights about the structure and the epistemological motivation of QT.
In the last two years the information-theoretic program entered the real of QFT, leading to a quantum cellular automata (QCA) extension of QFT. The quantum automaton is the minimal-assumption extension to the Planck and ultra-relativistic scales of QFT. The QCA can describe localized states and measurements that are unmanageable by QFT. Without requirement of relativistic covariance and on the basis of simple general information theoretic postulates, (as the homogeneity of interactions and the quantum Church-Turing postulate), a unique minimal automaton is derivable in d=3 space-dimensions that recovers exactly the Dirac dynamics for low momenta and small mass, but provides also a unified description for the Planck scale. It leads to powerful predictions, e.g. a bound on the inertial mass, without using GR (e.g. based on arguments as mini-black holes). The automaton theory looks as a very promising framework for quantum gravity, since it is quantum ab-initio, with relativistic covariance as emergent and not assumed a priori, it is free from all the problems arising from continuum, it doesnâ€™t suffer violations of causality, and has no divergences. It is the natural scenario to accommodate the quantum holographic principle. Lorentz covariance and all other symmetries are violated in the ultrarelativistic Planckian regime, and are perfectly recovered at the Fermi-scale, making the QCA the perfect testing scenario for symmetry and Lorentz violations. (Giacomo Mauro D'Ariano)
Quantum Mechanics: quantum technologies and foundational problems
Quantum mechanics can be seen as a useful tool to achieve practical goals such as computation, communication, and precise measurements. These are all aspects of the fledgling field of quantum technology. In stark contrast, from the foundational point of view, quantum mechanics has some obvious gaps that mostly stem from its counter-intuitive nature.
Research in this field deals with both these aspects. Regarding quantum technologies, the main emphasis and results stem from quantum metrology. It studies how quantum effects (e.g. entanglement and squeezing) can be useful to increase the precision of measurements and to achieve the ultimate bounds on precision that quantum mechanics imposes (e.g. from the Heisenberg uncertainty relations). In quantum metrology we study protocols for specific types of measurements (e.g. position measurements, imaging, interferometry, etc.), but also the general theory of quantum metrology. Another important quantum technology aspect refers to quantum communication: communication requires information carriers that are physical systems. Quantum mechanics imposes limits to the amount of information they can carry through a communication channel. A still outstanding problem is the extension of Shannon's information theory to the quantum domain. Important results have been found that refer to the communication of information through optical and radio communication channels. Finally, still in the context of quantum technologies, many different quantum devices and protocols have been developed. For example, we developed and analyzed the quantum random access memory (QRAM), a fundamental component of future quantum computers. Another useful tool in the quantum toolbox stems from the unconditionally secure cryptography that quantum mechanics allows: cryptographic communication schemes that cannot be intercepted (without violating the laws of physics). Different quantum cryptographic protocols have been developed, for example for the cryptographically secure query of a database or for cryptographically secure computation.
Regarding the foundational aspects, we investigate some of the most problematic aspects of quantum mechanics, such as the origin of quantum probabilities, the quantum origin of the arrow of time, and the emergence of a quantum spacetime. These are all explored in the context of the quantum theory of measurement, that is a unifying trait for all these researches.
In conclusion, our research spans from practical schemes that constitute an indispensable toolkit for the approaching quantum technology era up to the investigation of some of the deepest mysteries in the foundations of modern quantum mechanics. (L. Maccone)
Magnetic Resonances in Condensed Matter
The research activity of the NMR group is focused on the study of the microscopic physical properties of matter by combining local probes techniques, as nuclear magnetic resonance (NMR) and muon spin resonance (μSR), with techniques of macroscopic character as the SQUID magnetometry or the adiabatic calorimetry. The group is presently addressing three main research topics: a) superconducting materials; b) low-dimensional and molecular magnetism; c) biomedical applications.
a) The work in progress on the iron-based and high temperature superconductors aims at understanding the microscopic mechanisms involved in the Cooper pair formation. By means of NMR and μSR spectra and relaxation rates measurements, the symmetry and amplitude of the superconducting order parameter is investigated as a function of different external parameters as the temperature, the magnetic field intensity, the pressure and the charge doping. These measurements allow also to study the modifications in the low-energy excitations in the normal state and to investigate the nanoscopic coexistence of the magnetic and superconducting ground-states which characterizes these materials The group is also involved in the study of the flux lines lattice motions in the mixed-state, a problem which is of significant interest both for the future technological applications of the superconductors and for the fundamental aspects involved.
b) The NMR group has a well established activity on the molecular magnets, which have attracted remarkable attention in recent years owing to their possible application as logic units. The aim is to study by means of magnetic resonance techniques the changes in the local spin configuration and in the low-frequency dynamics upon varying the number of spins from even to odd, their magnitude or the local crystal field and to investigate the formation of entangled spin-states. Part of the research activity on low-dimensional magnets is centred on the study of novel exotic ground-states which arise in frustrated magnetic systems, as the spin nematic, spin-ice and spin-liquid ones, or in intermetallic compounds.
c) The research activity in the biomedical area involves, first of all, the development of novel techniques and of materials which allow to improve the performance of Magnetic Resonance Imaging (MRI) diagnosis. In the last years the group has been involved in the development of the dynamical nuclear polarization technique which allows to open a new route towards in vivo molecular imaging of the metabolic processes. Moreover the group is studying functionalized magnetic nanoparticles which can be used either as MRI contrast agents, or for the drug delivery or, eventually, for the therapy of certain pathologies through hyperthermia. The group collaborates also in the development of the Boron Neutron Capture Therapy (BNCT) technique by studying the possibility to map the boron distribution prior to neutron irradiation. (Pietro Carretta)
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