Table of contents

The Young Researcher Meeting (www.yrmr.it) has confirmed once again this year the enthusiasm and determination of Ph.D. students, postdoctoral fellows and young researchers to play a major role in the scientific progress. Since 2009, we regularly gather together to discuss the most recent developments and achievements in Physics, firmly convinced that sharing our expertise and experience is the foundation of research activity.

The format we chose is an informal meeting primarily aimed at graduate students and postdoctoral researchers, who are encouraged to present their work in brief presentations that provide genuine engagement of the audience and cross-pollination of ideas. One of the main purposes of the conference is to create an international network of young researchers, both experimentalists and theorists, and fruitful collaborations across the different branches of Physics.

After four editions that strengthened it, the Young Researcher Meeting 2014 was held at the International School for Advanced Studies - SISSA, Trieste, for the second time. The fifth appointment was a two-day conference on July 14th-15th 2014. It has been sponsored by a number of research groups of SISSA, the University of Udine and the Solar Physics group of the University of Rome "Tor Vergata", thus gathering even broader support than previous editions. The success of this year event is testified by an increased number of participants and institutions all around Europe. This resulted in an extremely rich and interactive poster session that covered several areas of pure and applied Physics.

With the intent of broadening the contents and stimuli adopting multidisciplinary tools, the YRM 2014 hosted the workshop "Communicating Science" held in collaboration with SISSA Medialab. This choice reflects the growing importance of the outreach activity performed by scientists, especially at the earliest stages of their career, as a way of increasing their expertise and developing soft skills. Engaging the public and finding unconventional ways to communicate results turn out to be real assets in improving the quality of presentation of current research to peers, as well as to the general public.

In this volume, we collect part of the contributions that have been presented at the conference. They cover topics in astrophysics and cosmology, particle and theoretical physics, soft and condensed matter, medical physics and applied physics. Given the recent experimental achievements in particle physics and cosmology, several contributions were focused on the latest results obtained in these fields, presenting the impact of experiments such as LHC and Planck to the community of young researchers and forecasting the future goals in these areas of research. Particular interest was aroused by the session fully dedicated to applied Physics and conservation of cultural assets. Besides the intrinsic scientific value of the discussed topics, the increasing relative weight of the applied Physics session is a demonstration of the benefits that fundamental science brings to the community.

YRM Organising and Editorial Committee

Fabio Agostini (fabio.agostini31@gmail.com) Telespazio A Finmeccanica Thales Company

Claudia Antolini (claudia.antolini@sissa.it) SISSA - Scuola Internazionale Superiore di Studi Avanzati and Fudan University

Rossella Aversa (raversa@sissa.it) SISSA - Scuola Internazionale Superiore di Studi Avanzati

Giordano Cattani (giordano.cattani@gmail.com)

Marco Di Stefano (distefan@sissa.it) SISSA - Scuola Internazionale Superiore di Studi Avanzati

Maria Longobardi (marialongobardi@gmail.com) Department of Condensed Matter Physics, University of Geneva

Matteo Martinelli (martinelli@thphys.uni-heidelberg.de) SISSA - Scuola Internazionale Superiore di Studi Avanzati and Institut fur Theoretische Physik

Alice Miceli (alice.miceli@uniroma2.it) Physics Department, University of Rome Tor Vergata

Marina Migliaccio (mm858@ast.cam.ac.uk) Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge

Francesco Paci (fpaci@sissa.it) SISSA - Scuola Internazionale Superiore di Studi Avanzati

Davide Pietrobon (davide.pietrobon@berkeley.edu) University of California at Berkeley

Emanuela Pusceddu (emanuela.pusceddu@gmail.com) Institute of Biometeorology CNR

Francesco Stellato (francesco.stellato@roma2.infn.it) INFN Roma Tor Vergata

ACKNOWLEDGEMENTS

The organisers of the 5th Young Researcher Meeting would like to thank all the scientists who participated to the meeting. We furthermore thank all our sponsors that are listed below for supporting the event. We are grateful to the International School for Advanced Studies (SISSA) for hosting the conference for the second time, and to its director, Prof. Guido Martinelli, for his support and advice. We owe gratitude to SISSA Medialab, for organising the public event on science communication and providing technical support throughout the entire meeting. The publication of the proceedings of the conference is partially supported by the Solar Physics group in Tor Vertaga; we also acknowledge support from the University of Udine.

The event was broadcast live by OggiScienza (http://oggiscienza.wordpress.com). The complete videos of the meeting can be found at the YRM Youtube channel

https://www.youtube.com/channel/UCw3roeK9oC4NPc-sRQ2t0rg

	International School for Advanced Studies (SISSA), Trieste
	PRIN 2010-2011 (MIUR 2010YJ2NYW_001) - "Symmetries, Masses and Mysteries: Electroweak symmetry breaking, flavor mixing and CP violation, and Dark Matter in the LHC era" - SISSA, Trieste
	Molecular and Statistical Biophysics Group - SISSA, Trieste
	PRIN 2012 (2012CPPYP7_006) - "Theoretical Astroparticle Physics" - SISSA, Trieste
	PRIN 2010-2011 (MIUR 2010NHBSBE_008) - "L'Universo oscuro e l'evoluzione cosmica dei barioni: dalle survey attuali a Euclid" - SISSA, Trieste
	Department of Chemistry, Physics and Environment of the University of Udine
	Solar Physics Group - Department of Physics of the University of Rome "Tor Vergata"

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The ATLAS experiment at the LHC, in conjunction with the discovery of the Higgs boson is looking for signs of physics which go beyond the Standard Model of Electroweak interactions. Among possible theories for physics beyond Standard Model, Supersymmetry seems to be the most promising one. This theory indeed addresses the Standard Model naturalness problem and offers a perfect candidate for the dark matter. Within this scenario the search for a supersymmetric partner of the top quark, called stop, plays a key role. The ATLAS Experiment has developed a dedicated strategy for the discovery of this particle, focusing on achieving a complete coverage of the available parameter space for this particle, based on the combined search for all of its possible decay modes. The results obtained using the complete ATLAS 2012 statistics will be presented, targeting different decay modes and explaining the procedure to obtain the exclusion limits on the existence of a supersymmetric partner of the top quark at the electroweak scale.

The LAGUNA/LBNO collaboration proposes a new generation neutrino experiment to address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, Liquid Argon (LAr) double phase Time TPC (Time Projection Chamber), the fiducial mass of the detector is set to 20 kt in its first stage. The detector will be situated at 2300 km from CERN: this long baseline provides a unique opportunity to study the neutrino flavour oscillations over the first and second oscillation maxima and to explore the L/E (Length over energy) behaviour. The near detector is based on a high-pressure argon gas TPC situated at CERN. I will detail the physics potential of this experiment for determining without ambiguity the mass hierarchy (MH) in its first stage and discovering CP violation (CPV) using the CERN SPS beam with a power of 750 kw. The impact of the assumptions on the knowledge of the oscillation parameters and the systematic errors are very important and will be shown in detail to prove the force of the experiment assuming realistic and conservative parameter values.

In this work, we study how recent cosmological datasets in combination with particle physics results are able to constrain the neutrino mass scale. In particular, we present current bounds on the electron neutrino mass m_β, the effective Majorana mass m_ββ and the total neutrino mass Σm_v and we discuss the sensitivity required to future experiments in order to address the issue of neutrino hierarchy.

We review the state of the art of the study of the cosmic structure on ultra-large scales as is forecast to be achievable by the oncoming generation of intensity mapping experiments. We focus on intensity maps of the redshifted 21 cm line radiation of neutral hydrogen (Hi) in the post-reionisation Universe. Such measurements will be performed by future radio telescopes such as for instance the Square Kilometre Array and will allow for surveying the biggest volume ever of cosmic structure. After having shown why it is valuable to scrutinise such extremely large cosmic scales – they will supply crucial information about the physical processes at play at early times – we concentrate on primordial non- Gaussianity as a working example. We illustrate that Hi intensity mapping experiments can place tight bounds on different inflationary scenarios via constraining the non-Gaussianity parameter, f_NL, with an error close to 1.

Beyond the standard cosmological model where the late-time accelerated expansion of the universe is driven by a cosmological constant, the observed expansion can be reproduced as well by the introduction of an additional dynamical scalar field. In this case, the field is expected to be naturally coupled to the rest of the theory's fields, unless a (still unknown) symmetry suppresses this coupling. Therefore, this would possibly lead to some observational consequences, such as space-time variations of nature's fundamental constants. In this paper we investigate the coupling between a dynamical Dark Energy model and the electromagnetic field, and the corresponding evolution of the fine structure constant (α) with respect to the standard local value α₀.

We study the detailed time-evolution of the fine-structure constant α in the string- inspired runaway dilaton class of models of Damour, Piazza and Veneziano [1, 2]. We provide constraints on this scenario via the time-variations of the fine-structure constant α as measured by spectroscopic experiments and we explore ways to distinguish the dilaton runaway models from other alternative.

We extended recent semi-analitycal galaxy formation models, that fitted the far- infrared (FIR) to millimeter wave luminosity functions and ultraviolet (UV) luminosity functions up to high redshifts, in order to take into account additional UV data and Hα luminosity functions. The latters are tracers of star formation in evolved galaxies at low redshifts. Using the relations between star formation rate (SFR) and radio (synchrotron and free-free) emission, we obtained predictions for the counts of star-forming galaxies down to sub-nJy fluxes. These will be very useful for the new generation of radio telescopes, thanks to which it will be possible to investigate smaller and smaller radio fluxes (down to nJy), making the detection of little SFR possible.

We study the HI Rotation Curve of the spiral galaxy NGC 3198 in terms of mass decomposition. We model the Rotation Curve in the framework of different models for the Dark Matter distribution: the Burkert profile and NFW profile. We show that Universal Rotation Curve (Burkert halo+stellar disk+gas disk) fits data accurately. Instead, the NFW (NFW halo+stellar disk+gas disk) model gives non-physical values of NFW halo parameters.

Several scenarios have been proposed to account for the formation and evolution of galactic bulges and to explain the variety of their observed properties. Both the intrinsic shape and dynamical structure of bulges depend on the mechanisms and timescales of their formation. We are deriving the intrinsic axial ratios of the bulges of a sample of unbarred lenticular galaxies to look for a possible relationship with their known orbital structure. Preliminary results show that the orbits of stars of the triaxial bulge of NGC 4476 are more anisotropic than those in the axisymmetric bulge of NGC 4249 hinting at a different formation process.

We investigate the metallicity distribution function (MDF) of the Galactic halo and the relative fraction of Carbon-normal and Carbon-rich stars using the semi-analytical code GAMETE. The code reconstructs the hierarchical merger tree of the Milky Way (MW) and follows the star formation history and the metal evolution in individual progenitors, including for the first time the formation and evolution of dust. We predict scaling relations between the dust, metal and gas masses for MW progenitors and compare them with observational data of galaxies at 0 ≤ z < 6.3. We find that the relative contribution of C-normal and C-enhanced stars to the MDF and its dependence on [Fe/H] allow to discriminate among different Pop III/II transition criteria as well as between different Initial Mass Functions (IMFs) and supernova (SN) yields for Population III stars.

The soLar group University of Tor vergata fabry-perot INterferometer (LUTIN) is a narrow band filter based on an optical cavity resonator with Capacitance-Stabilised Etalon (CSE) control. The prototype, developed at the University of Rome Tor Vergata, is part of the study for the narrow band channel of the ADvanced Astronomy for HELIophysics (ADAHELI) mission designed to investigate the dynamics of solar atmosphere as part of the Italian Space Agency (ASI) Small Missions program. We developed the electro-mechanical control for the optical cavity, necessary for the tuning and the gap control of the instrument. We present the measures of the microroughness of the optical plates, performed with a Zygo interferometer, and the instrument spectral stability behaviour in on-optical-bench open-air mode. The measures refer to the upgraded version of the LUTIN prototype, which mounts the new λ/60 optical plates.

Searching for a 3D multiferroic material with a strong magnetoelectric coupling and high critical temperature is a major challenge in modern condensed matter research. CuO is the building block of high-temperature superconductors and triggered a new interest when it was established as potential high temperature multiferroic. We have succeeded in growing high quality single crystals of CuO with two different methods, namely the floating zone under high oxygen pressure and the chemical vapor transport growth. The fact that we are able to grow crystals of the same compound by different techniques makes it possible to study the effect of slightly different chemical compositions, various kinds of defects and variable strain on the final properties of the compound. Optical spectroscopy has been deployed to study the optical response of cupric oxide. Thereby we achieved a deeper insight of the optical, electronic and structural properties by measuring the infrared reflectivity under a magnetic field and the Raman shift under hydrostatic high pressure.

Density-matrix renormalization group results are reported for the excitonic transitions in zigzag graphene nanoribbons within the framework of the simple Hubbard model. This work shows that a one-dimensional quantum lattice model with open boundary conditions is able to capture the many-body features in the low-energy electronic spectra of these systems alongside the size dependence on the ribbon width. The obtained results agree with the trends of charge and spin excitation gaps available from quantum chemistry predictions.

The electronic properties of graphyne and graphdiyne consisting of sp and sp² hybridized carbon atom have been investigated within the density functional theory (DFT) method. The corresponding changes in the electronic properties due to systematic functionalization by fluorine at different possible sites are reported. Our band structure calculations clearly infer that all fluorographyne are wide band gap semiconductor and the band gap can be tuned by fluorination and the possibility of modulating the band gap provides flexibility for its use in nanoelectronic devices. Projected density of state (PDOS) analysis provides the clear idea about the bonding nature of these novel materials in details and Crystal Orbital Hamilton Population (-COHP) analysis shed insight on the orbital participating in bonding and antibonding.

We report on the study of a plasmonic nanostructure that could be adopted as platform for emitting and sensing applications. Several devices have been prepared and characterized by atomic force microscopy (AFM) and Fourier transform micro-reflectance (FT- pR) techniques. In addition, a modelling via finite-difference time-domain (FDTD) simulations have been developed in order to interpret the morphological shape and the optical response of the considered structures. Until now, remarkable performances as surface plasmon resonance (SPR) based optical sensor have been founded. Moreover, we are performing preliminary trials in order to establish a coupling between photoluminescence (PL) features of suitable emitters with respect to the plasmonic resonances.

We study the electronic and local structural properties of pure and In-substituted β-Ga₂O₃ using density functional theory. Our main result is that the structural energetics of In in Ga₂O₃ causes most sites to be essentially inaccessible to In substitution, thus limiting the maximum In content to somewhere between 12 and 25 % in this phase. We also find that the band gap variation with doping is essentially due to "chemical pressure", i.e. volume variations with doping.

Bismuth sulfide is a promising n-type semiconductor for solar energy conversion. We have explored the colloidal synthesis of Bi₂S₃ nanocrystals, with the aim of employing them in the fabrication of solution-processable solar cells and to replace toxic heavy metals chalcogenides like PbS or CdS, that are currently employed in such devices. We compare different methods to obtain Bi₂S₃ colloidal quantum dots, including the use of environmentally benign reactants, through organometallic synthesis. Different sizes and shapes were obtained according to the synthesis parameters and the growth process has been rationalized by comparing the predicted morphology with systematic physical-chemistry characterization of nanocrystals by X-ray diffraction, FT-IR spectroscopy, Transmission Electron Microscopy (TEM).

(70-x)SiO₂-30HfO₂ -xP₂O₅ (x= 5, 10 mol %) glass planar waveguides activated by 0.5 mol% Er³+ ions were prepared by sol-gel route. Several phosphorous precursors have been investigated for the synthesis of a dielectric stable sol useful for the realization of planar waveguides. The waveguides were investigated by different diagnostic techniques. The optical properties such as refractive index, thickness, number of propagating modes and attenuation coefficient were measured at 632.8 and 543.5 nm by prism coupling technique. Transmission measurements were carried out in order to assess the transparency of the deposited films. Photoluminescence measurements and lifetime decay curves of the Er³+ transition ⁽⁴I_13/2 → ⁴I_15/2) were performed in order to investigate the role of P₂O₅.

We recently developed a computational model of tumour growth. It is a cell- based model that can simulate the growth of multicellular tumour spheroids up to more than one million cells. The simulation program is very demanding and simulation time severely limits the integration of additional biological details, and indeed, at the moment, a typical simulation run requires tens of days to be completed. A new version of the code that exploits Graphics Processing Units (GPUs) to boost performance is being developed. In this paper we describe the design and implementation of a nearest-neighbour search (NNS) algorithm suitable to run on GPU. The algorithm will be integrated in the original code to manage the geometrical calculation in the simulation of the spheroid. Initially the stand alone NNS algorithm was tested for spheroids of different size: better efficency was obtained for bigger spheroids. Eventually the code was integrated in the whole simulation code and preliminary runs gave a speed up of about 5 for spheroids of relatively small size (15000 cells).

Finding new ways to fight cancer is essential to increase the patients life expectancy. This paper reports the latest results of the project CHIRONE finalized to increase the potential of the Radio Guided Surgery through the use of β⁻ emitting radio-tracers and β⁻ probes. This innovation could overcome the present main limiting factor represented by a diffuse background due to the high penetration power of the gamma radiation used. We created a prototype of β⁻ probe and in this paper we report measures of photon efficiency, acquired with commercial photons sources. Then we estimated the signal and background rates in realistic cases of meningioma through a simulation. The device is able to detect residuals of 0.1 ml in 1 s with an administered activity less than 3 MBq/kg.

The cadmium yellow paints (CdS) used in impressionist and modernist paintings in early 1900s are undergoing several deterioration processes, including whitening and discoloration. A relevant effect produced at the surface of the paintings is the growth of discolored crusts, formed mainly by white globular hydrated cadmium sulfate (CdSO₄*nH₂O) and cadmium carbonate (CdCO₃). Recent studies ascribe to an initial photo-oxidation process of CdS the input for the formation of such whitish compounds. In order to understand, at atomic level, the oxidation and hydration mechanisms of these whitish globules, we present the early stages of a theoretical study of the interaction between the hexagonal {10.0} surface of CdS and O₂ and H₂O molecules to simulate the combined effects of exposure to air and humidity. For this purpose, we adopted a first principles method within the framework of the Density Functional Theory (DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft pseudopotentials.

The diagnostic investigations are an important resource in the studies on Cultural Heritage to enhance the knowledge on execution techniques, materials and conservation status of a work of art. In this field, due to the great historical and artistic value of the objects, preservation is the main concern; for this reason, new technological equipment has been designed and developed in the Physics Departments of the Universities of Ferrara and Bologna to enhance the non-invasive approach to the study of pictorial artworks and other objects of cultural interest. Infrared (IR) reflectography, X-ray radiography and computed tomography (CT), applied to works of art, are joined by the same goal: to get hidden information on execution techniques and inner structure pursuing the non-invasiveness of the methods, although using different setup and physical principles. In this work transportable imaging systems to investigate large objects in museums and galleries are presented. In particular, 2D scanning devices for IR reflectography and X-ray radiography, CT systems and some applications to the Cultural Heritage are described.

We present the main line of the Dynamical Bridge method applied to electromagnetic (EM) fields. In this framework, we show the equivalence between the Born- Infeld theory written in a given curved space to the Maxwell's one written in the flat space. In the limit of weak EM fields, we obtain a geometrical contribution to the anomalous magnetic moment of the leptons and, finally, we compare it with experimental data.

Globular clusters are stellar systems in which thermodynamics plays a fundamental role. Classically these systems are described by non-relativistic single mass King distribution function, which derives from the Fokker-Planck equation by taking into account stellar collisions and host galaxy tidal confinement. In terms of statistical mechanics the available phase space is restricted and so thermodynamics variables assume different meaning respect to the Boltzmann distribution. Through the introduction of an effective potential, which stands for the galactic tidal forces, a new thermodynamic theory is developed and theoretical energy and specific heat profiles are given for globular clusters.

We investigate the presence of instabilities in the Cascading DGP model. We start by discussing the problem of the cosmological late time acceleration, and we introduce the modified gravity approach. We then focus on brane induced gravity models and in particular on the Cascading DGP model. We consider configurations of the latter model where the source term is given simply by vacuum energy (pure tension), and we study perturbations at first order around these configurations. We perform a four-dimensional scalar-vector-tensor decomposition of the perturbations, and show that, regarding the scalar sector, the dynamics in a suitable limit can be described by a master equation. This master equation contains an energy scale (critical tension) which is related in a lion-trivial way to the parameters of the model. We give a geometrical interpretation of why this scale emerges, and explain its relevance for the presence of ghost instabilities in the theory. We comment on the difference between our result, and the one present in the literature, and stress its importance regarding the phenomenological viability of the model. We finally provide a numerical check which confirms the validity of our analysis.

The time evolution and stationary behaviour of local observables is studied after a quantum quench of the magnetic field in the transverse field Ising chain, when the initial state is chosen as an excited state of the pre-quench Hamiltonian. Relaxation to the Generalized Gibbs Ensemble is proved. Equal-time longitudinal two point function and entanglement entropy are analytically derived for a class of excited states which confirm the light-cone spreading of correlations also starting from excited states.

A simple 1D toy model to study one-neutron transfer reactions is developed. It is based on the solution of the time dependent Schroedinger equation for a particle initially bound by a fixed potential well, perturbed by a second moving potential, which accounts for the second partner of the reaction. At the end of the time evolution it is possible to evaluate the probability of the transfer of the particle from a potential to the other, as well as the transfer to continuum states in the case of weakly-bound systems. Although rather simple, the model accounts for most of the physical characteristics of these kind of reactions: such as the existence of an optimum Q-value and the dependence on the parameters defining the relative motion of the two potentials.