1-Geometrical aspects of jet quenching in small systems

• Francisco Barreiro (IST/LIP)

The Quark-Gluon plasma (QGP) is a state of hot and dense matter where quarks and gluons are deconfined and is produced in ultra-relativistic heavy-ion collisions, at both RHIC (BNL) and at the LHC (CERN). This state is believed to have existed in the first microseconds of our universe's lifetime. Heavy ion collisions can be classified as soft, responsible for the production of QGP, or hard, where partons with high momentum are produced and pass through the medium (vacuum or QGP), along which they fragment into sprays of particles, called jets. Jets interact strongly with QGP, which can lead to a modification of its properties (this phenomenon is known as Jet Quenching). Such modifications provide detailed information on QGP properties. In line with the approach of “run 3” at LHC, where small systems collisions will be performed, in my thesis I aim to study the geometrical aspects of jet quenching in small systems. More specifically, in systems of different geometry but same total size (eg, central OO collisions and peripheral PbPb collisions). However, current Monte Carlo event generators used to explore the phenomenology of jet quenching fail short of addressing the geometrical aspects of jet quenching in small systems. Therefore, initially it will be necessary to develop a small systems initial geometry model and implement it in JEWEL, a Monte Carlo event generator.

2-Proton irradiation effects on nanomembranes and FETs based on h-BN

• Tiago Fernandes (IST)

Hexagonal boron nitride (h-BN) is a semiconductor with a very large bandgap of almost 6 eV. It can not only be used as a deep UV light emitter/detector, but its high thermal stability, mechanical strength, resistance to oxidation and high thermal conductivity make it an excellent dielectric material. Like in graphite, thin membranes can be mechanically exfoliated and used in nanodevices. In this thesis, we will study the effects of proton irradiation on h-BN using techniques like Ion Induced Beam Luminescence, Thermoluminescence and X-ray Diffraction, analysing the creation of defects in the lattice and the appearance of intermediate levels in the bandgap, which are crucial for single photon emitters, used in quantum communications. We will also produce FETs using h-BN nanomembranes as the dielectric and evaluate the performance of the devices under proton irradiation.

3-Photon Pair Source

• Gonçalo Teixeira (IST - IT)

One of the essential ingredients for photonic quantum technologies, namely secure quantum communications, are entangled photon pair sources. Entanglement is a quantum property of particles that allows secure communications, in particular in the context of device-independent (DI) cryptography. The entangled photon pair source may additionally be used as a heralded single photon source for semi-device independent (SDI) quantum key distribution (QKD). The objective of this project is to develop an entangled photon pair source for DI and SDI QKD. To generate quantum entanglement, we will use non-linear optical processes, such as spontaneous parametric down-conversion, linear optics elements, and photon detectors which are sensitive enough to detect the arrival of a single photon. The work will be developed at the Quantum Technologies Laboratory of the Physics of Information and Quantum Technologies Group (IT and IST), and will involve the collaboration of Dr. Emmanuel Zambrini Cruzeiro.

4-Two-fluid models in solid-state plasmas

• Vasco Pinhão (IPFN)

The possibility of producing graphene samples of extreme purity has revealed an electronic regime that was realized theoretically in the 1960s, but that always lacked experimental confirmation - the hydrodynamic regime. In this regime, electron-electron collisions dominate over scattering with disorder - phonons and impurities, and electronic dynamics can be described with classical fluid equations. By applying a hydrodynamical model to graphene-based bilayer systems, we will search for physical mechanisms that can sustain plasmonic instabilities, i.e collective charge oscillations whose amplitude grows exponentially in time until a saturation regime is reached. Maintaining these plasma oscillations after they've reached saturation is a challenge with great technological interest, since it offers a promising path for the development of tunable sources of TeraHertz radiation.

5-Linearized General Relativity in Hyperboloidal Slices

• Inês Andrade Rainho (CENTRA — Instituto Superior Técnico)

A problem that remains unsolved in Numerical Relativity is the calculation of the waves all the way out to infinity from first principles. It may seem impossible to do this using a computer since they have only finite memory. But it turns out that by choosing an appropriate set of coordinates adapted to outgoing waves and considering the fall-off of the gravitational field as we approach infinity it is possible to do so. In this project, the aim will be first to understand gauge fixing for the linearized Einstein Equations from the free-evolution point of view employed in mathematical and numerical relativity. The second goal will be to understand the use of compactified hyperboloidal slices to reach null infinity in the computational setting.

6-Dark Mater Searches at the LHC

• Daniel Neacsu (IST and CFTC)

The Standard Model (SM) of particle physics has provided countless highly accurate predictions over the years, making it one of the most successful theories in physics. However, once under the scrutiny of increasingly precise experiments some discrepancies have emerged. The long standing discrepancy in the anomalous magnetic moment of the muon was one of the first indication of the need for new physics involving lepton flavour universality violation. Even more recently, the decays of B-mesons have also been found to indicate lepton violation. In addition, the already well established fact of the existence of Dark Matter poses yet another problem that needs to be solved. By extending the SM with a set of new fields with the freedom to couple to the SM fermions a class of models that can solve all of these problems is created. As such, these models have gained a lot of traction and are currently being extensively studied. This project will examine the searches that can be realized at the Large Hadron Collider (LHC) involving the production of Dark Matter. A careful characterization of the missing energy distributions that can arise from these models will potentially provide an invaluable channel of further constricting their properties and parameters.

7-New coupling mechanisms and exchange bias in ferrimagnetic spin valves

• Mariana Caseiro (IST/INESC-MN/HZB)

The exchange bias (EB) effect has become a vital topic of research on the field of spintronics. Numerous device applications like random access magnetic storage units and spin valves rely on it for improved stability in temperature and field. In particular, it has been observed that perpendicular exchange bias (PEB) demonstrates a larger thermal stability for stored information and is consequently more desirable to have in applications. The challenge arises in creating PEB efficiently. In the majority of cases, the PEB is set through field-cooling or by in situ field growth procedures, which are time consuming or not as accessible. A novel method would be to make use of ferrimagnetic spinvalves, with materials such as CoDy or GdFeCo, which have been proven to exhibit perpendicular anisotropy. At the interface between ferrimagnets, all spin pairs will contribute to the appearance of an EB. If the coupling between ferrimagnetic layers is too strong however, EB cannot occur. To circumvent this, a thin interlayer spacer is introduced in order to partially decouple the two layers. Thus, the exchange coupling can be tuned through the variation of the thickness of the spacer layer, and a perpendicular exchange bias can be induced and reversed at room temperature. This method requires further study, namely on the magnetic interactions occurring at the interface and on the choice of spacer. It would be of interest to understand the coupling mechanisms for exchange bias and their dependence on the magnetic properties of the system.

8-Automated ECG classification using Deep Neural Networks to predict arrhythmia recurrence in patients with atrial fibrillation

• João Galvão (IST)

It is currently not possible to predict the evolution of patients with arrhythmia after clinical intervention. For that reason, we intend to pursue this goal using a computational approach, consisting in neural networks that take electrocardiograms as inputs. It is believed that the P-wave in the surface electrocardiogram is related to the arrhythmia condition, and holds predictive features concerning the patient's evolution. The first step of our project is to filter the noise of the electrocardiogram, and then we apply machine learning techniques to all the data we have. By doing so, we anticipate an algorithm for automated ECG beat classification that predicts arrhythmia evolution in patients. This will be very important for clinical purposes and medical decision.

9-Probing the Standard Model in EFT Global Fits at the LHC

• Pedro Lagarelhos (LIP)

The Standard Model of Particle Physics (SM) describes remarkably well all the known fundamental particles and their interactions. In spite of its large success, it is by now clear that it cannot be the ultimate theory since it fails to explain some observed physical phenomena. For many years, the Large Hadron Collider (LHC) experiments have tried to identify signs of New Physics but, up to now, no Physics Beyond the Standard Model (BSM) have been discovered, so far. In many BSM models, new Physics is characterised by a mass scale expected to be higher than the current centre-of-mass energies available at colliders, which may well be the reason why BSM has not been discovered yet. Nevertheless, even in the case that new particles are too heavy for direct detection at the LHC, a model-independent Effective Field Theory (EFT) approach is a powerful tool to probe the effects of these new particles and/or interactions at low-energy, in the absence of any clue on the full theory underlying the SM. This project focuses on the search of signs of Physics BSM by studying the $Wtb$ vertex structure in top quark production and decay at the High Luminosity phase of the LHC (HL-LHC). SM Monte Carlo events, generated at a centre-of-mass energy of $14$ TeV and corresponding to the full expected integrated luminosity at the HL-LHC ($3000$ fb$^{−1}$), were used in the analysis, after passing the simulation of the ATLAS detector. Several signal regions, corresponding to $t\bar{t}$, single top $t$-channel and associated production $Wt$ semileptonic events, were considered simultaneously in a new approach using a global analysis of several physics channels. Ultimately, a global fit to specific angular distributions, in all signal regions, will be performed in order to extract the precision with which the EFT Wilson coefficients can be probed up to the HL-LHC.

10-Solid-state High Harmonic Generation

• André Antunes (GoLP/IPFN - Instituto Superior Técnico)

The nonlinear interaction of ultrashort laser pulses with solids, namely the process of solid-state High Harmonic Generation (HHG), has brought about a surge of scientific interest due to the prospect of creating novel compact Extreme Ultraviolet (XUV) sources and harnessing ultrafast dynamics of electrons in solids. Possibilities of engineered materials with tailored optical responses, or methods for all-optical band structure mapping through HHG keep driving this area of research forward. Our main goal is to study the strong-field interactions that characterise HHG in solid-state materials through state-of-the-art modelling. Such models will be used to understand the results of previous experimental campaigns from the VOXEL and L2I labs at IST. Furthermore, the modelling can guide future experimental projects at the IST labs.

11-Continuous Measurements in Quantum Transport Setups

• João Costa (CeFEMA-Instituto Superior Técnico)

We can only obtain information from a system by means of measurements. However, they always leave a fingerprint behind as the system is left in a state that depends on the measurement outcome. Continuously monitored systems, such as quantum circuits and the closed fermionic chain, are known to exhibit very interesting critical phenomena in their entanglement content when we vary the measurements' strength. The latter is a good toy model for a quantum transport setup if we consider it coupled to two reservoirs. A generalization of the known results to the open case will be pursued in this thesis. As electronic systems are usually probed by transport measurements, it is natural to wonder which features of the entanglement phase transition can be detected from the outcome of such measurements. Thus, the answer to this question stands as the ultimate objective of my thesis.

12-Sensitivity of jet sub-structure observables to jet quenching in collisions of light nuclei

• Manuel Mariano (IST/LIP)

The Quark-Gluon plasma (QGP) is a state of hot and dense matter where quarks and gluons are deconfined and is produced in ultra-relativistic heavy-ion collisions, at both RHIC (BNL) and at the LHC (CERN). Jets (resulting from hard partonic collisions) that develop within the QGP are modified with respect to their vacuum counterparts (eg, jets produced in proton-proton collisions that develop in empty space) due to its interaction with the medium. Such interaction is referred to as jet quenching, and it provides detailed information on QGP properties. Current Monte Carlo event generators used to explore the phenomenology of jet quenching fail short of addressing the light nuclei collisions. One of the reasons for that, is the Glauber model used by such event generators. However, the future availability of collisions of light nuclei (OO during LHC Run3) calls for an update to these Monte Carlo generators. Therefore, the plan is to first develop a small systems initial geometry model and its event-by-event implementation in the JEWEL Monte Carlo event generators, and then make a comparative study of jet substructure, and their eventual geometrical biases, in collisions of light and heavy nuclei.

13-Signatures of Ultralight Bosonic Fields in Black Hole Binaries

• Ricardo Arana (Instituto Superior Técnico)

The recent detection of gravitational waves by the LIGO/Virgo collaboration has shown we have a new tool to study the physics of binary systems and compact objects, like Black Holes and Neutron Stars. One of the problems we are interested in studying is the existence of new types of particles beyond the Standard Model. Due to the instability of a process called superradiance, it is theoretically possible that ultralight bosons, which only interact through gravity and are weakly coupled to ordinary matter, condensate in the ergoregion of a black hole and, if they are in the presence of another compact object, such as in binary systems, the gravitational waves emitted by the binary will allow us to probe particles with mass between $10^{-20}$ eV (such as dark matter candidates) and $10^{-10}$ eV (like QCD axions) with future gravitational wave detectors like LISA. In this work, I will focus on the signatures of self-interacting scalar (spin-0) and vector (spin-1) fields due to different physical processes like tidal deformations and accretion effects.

14-Particle Physics Anomalies from Dark Matter

• Tomás Lopes (CFTC/CFTP)

In this project we propose an extension of the Standard Model which provides an origin for the evidence of lepton flavor universality violation in $b\rightarrow s l^+l^-$ decays and the long-standing muon $(g-2)$ anomaly. By considering a model which features a neutral scalar, we suggest a candidate for the role of dark matter particle. After studying the dark matter and flavour physics of the model, we perform a parameter scan and search for a parameter space of the model which explains all three new physics phenomena simultaneously.

15-Distributed Quantum Annealing

• Raúl Santos (IST)

Quantum algorithms have been shown to be faster, in theory, than the known classical approaches. This has been hard to demonstrate in reality, as it gets much harder to build large and reliable quantum computers. The idea of Distributed Quantum Computation then emerges from this, where multiple, smaller, quantum processors work in parallel to solve a problem that would otherwise only be possible in a single, much larger, quantum computer. By the implementation of tele-gates, which exploit quantum entanglement to achieve non-local quantum operations, it has been shown that distributed quantum computing is possible for the circuit model paradigm. Quantum annealers, devices that employ quantum annealing to make computations, have seemingly been forgotten from this idea. As far as we know, there there is no published research discussing the idea of Distributed Quantum Annealing. My thesis work will investigate possible protocols to distribute quantum annealing to various processors and will find out how well these found protocols work, both in the ideal case and in the presence of noise.

16-Life Prospection on Mars - Studying the Martian Subsurface Radiation Environment

• Igor Gago (IST/LIP)

This Thesis aims to study the martian subsurface radiation environment and to evaluate the survivability of extremophile organisms in the subsurface of Mars by analyzing the effects of this radiation environment on DNA molecules. The work is based on 2 main steps: First, modeling the Linear Energy Transfer spectrum in water of the ionizing field created by incident cosmic rays and solar event particles at different depths of the Mars subsoil up to 3m, using the detailed Martian Energetic Radiation Environment Model, and second, simulate the early radiation-induced damage on a simplified model of the DNA molecule, using the Geant4-DNA extension.

17-Optimization of the development of bacterial vaccines

• Sara Peça (Janssen Biologics BV)

In the world today it is more clear than ever the importance of accelerating the process of the production of vaccines as well as making it a commodity for the whole world. This project aims to validate a model that can be used to predict the performance of a novel vaccine candidate, more specifically a bacterial vaccine candidate by using molecular dynamics simulations, reducing costs and time. This type of vaccine is our best solution to solve the problem of antimicrobial resistance due to the widespread use of antibiotics over the last years. It will be performed in collaboration with the Bacterial Vaccines Department of Johnson & Johnson and connects the fields of physics and biology by applying known physical models and equations to biological compounds like proteins.

18-Optimisation studies for the pion-induced Drell-Yan measurement at the AMBER experiment

• Rita Silva (LIP Laboratorio de Instrumentacao e Fisica Experimental de Particulas (PT))

The AMBER experiment at CERN was recently approved to study the pion-induced Drell-Yan process. Drell-Yan is a hard process where a quark-antiquark annihilation originates a virtual photon that decays in the final state to a pair of oppositely charged muons. This process allows privileged access to the pion structure. The valence, sea and gluon contributions in the pion will be characterised with unprecedented accuracy, by using high intensity pion beams of both charges impinging in different nuclear targets.\\ The optimization of the experimental apparatus is a goal of the proposed work. By using Monte Carlo methods of physics simulation, and a Geant4-based software to simulate the detector effects, this project will study different possible configurations for target cells dimension and position, geometry and position of new vertex detectors, and optimal length and composition of a hadrons absorber to be included in the setup.

19-Integration Algorithms for Charged-Particle Dynamics in Magnetized Plasmas

• Manuel Assunção (Instituto Superior Técnico)

Plasma research has been conducted over a wide range of areas in physics. Due to the complexity of the physics that govern plasma behaviour, computer simulations have been used to bridge the gap between theoretical models and experimental results. Some plasma simulations involve computing the full orbit of charged particles under the influence of electric and magnetic fields. Such is the case for Particle-In-Cell (PIC) simulations of magnetized plasmas. The integration algorithm is a crucial component in those simulations, as it is responsible for updating the particle positions across phase-space. The purpose of my thesis is to develop, implement and test integration algorithms for non-trivial coordinate systems. In particular, integration algorithms with good conservation properties will be given a significant emphasis. The integration algorithms implemented in a particle-tracing code will be compared to those produced by standard approaches.

20-Modeling the COVID-19 pandemic: a multifaceted approach

• João Loureiro (SPAC/LIP - IST)

The COVID-19 pandemic struck the world with a force not seen since the Spanish flu. Our adaptation to it involved highly restrictive measures that constantly and drastically change the disease’s rate of transmission, which in turn makes predictions on COVID-19 numbers a difficult task. I will try to overcome this challenge using two distinct methods, one will be a mechanistic epidemiological model that embraces these measures, and the other a machine learning model that tries to bypass them completely.

21-Multi-Higgs Models

• Sérgio Carrôlo (CFTP)

The Higgs particle was predicted in 1964 and discovered at CERN on July 2012, earning Higgs and Englert the 2013 Physics Nobel Prize. This is a spin zero particle (scalar), necessary to give masses to the all other massive particles in the Standard Model of Electroweak interactions. But, there is no fundamental reason why there should be only one such scalar. Thus, as one achieves a more precise determination of the properties of the new particle, one should look for which signals there would be of extra particles; the so-called multi-Higgs theories. The aim of my thesis is to study a particular two higgs model and test its compatibility with experimental results in the quark sector.

22-Ga2O3 field effect transistors for sensor applications

• Miguel Martins (IST/INESC MN)

$\beta$-Ga$_2$O$_3$ has a very wide bandgap and can be exfoliated into membranes of nanometric thicknesses. For these reasons, a doped $\beta$-Ga$_2$O$_3$ nanomembrane can potentially be used to fabricate highly sensitive field effect transistors or charged molecule sensors. First, the fabrication of membranes through ion implantation will be studied. The next step is the optimization of a back-gate transistor based on this material, before switching to a top-gate geometry, which can more easily be adapted into a sensor.

23-Neural systems that process visual self-motion cues in larval fish

• Inês Vieira (IST)

We will use larvae that express a genetically encoded calcium indicator in all neurons to image whole-brain responses to translational and rotational optic flow patterns using a custom-built laser-scanning two-photon microscope. Having identified the brain regions responsive to visual motion, we will investigate how and where information from the two visual hemifields is integrated. Given the distinct locomotor patterns of the three species, we aim to test the proposal, derived from computational modeling of zebrafish data, that the observed functional organization reflects the constraints of the visual-locomotor mapping.

24-Looking for Decoherence effects in the Quark-Gluon plasma

• João Mesquita (LIP/IST)

Jets are colourless objects. Nevertheless, they keep information on their colour connections between one another. The pull vector observable supplies additional information regarding such connections in addition to the conventional properties, such as momentum and size. At ultra relativistic heavy ion collisions, one observes the presence of the Quark-gluon Plasma (QGP). Jet interaction with QGP leads to the surfacing of jet quenching effects. Previous work was performed to study colour correlation between colour singlet and colour octet dijet systems. We aim at assessing the extent of influence that the QGP medium has in inner jet structure, by extending this study to heavy ion collisions. To do that, we use the pull vector/ pull angle observable as measures of colour correlation inside jets. This work is meaningful because colour flow information is due to complement the kinematic properties of the jet allowing to identify irreducible backgrounds or even to match jets with the correct physical process. The results will have immediate impact and application at the current and future heavy-ion experimental data.

25-Extinction curves of type Ia supernovae from the Dark Energy Survey

• João Gonçalves (CENTRA — Instituto Superior Técnico)

Type Ia supernovae are a particular type of supernova that occur in binary star systems where one of the stars is a white dwarf. They are very important objects in cosmology as they can be used as distance indicators with up to 5% precision. The Dark Energy Survey is an astronomical survey that studies dark energy by analysing images in the near-ultraviolet, visible, and near-infrared to measure the expansion of the Universe using type Ia supernovae, among other objects. Its data, however, is affected by astrophysical and cosmological effects such as reddening and redshift. In this project I will study dust parameters in type Ia supernovae and estimate the dust contribution to the apparent magnitude of these objects in order to infer their intrinsic magnitude, which can be used to calculate their distance.

26-Semi-Device Independent protocols for QKD

• José Jesus (Instituto Superior Tecnico)

The development of Quantum Computers poses a serious risk towards modern day encryption. To solve this problem, Quantum Key Distribution (QKD), a collection of protocols that use quantum mechanics to achieve encryption, was proposed. In these types of protocols quantum correlations are exploited to achieve QKD even with untrusted devices, a remarkable achievement. Any potential faults introduced intentionally or unintentionally are detected automatically making these protocols inherently more robust. There are a few drawbacks to DI cryptography, namely it's extreme difficulty of implementation in the lab. Therefore, it is more important to take realistic approaches when creating cryptographic protocols whilst trying to preserve the interesting ideas of device independence. Such protocols are known as Semi-Device independent (SDI) protocols and require a well-founded assumption about the measuring devices. These protocols are the subject of study in my master thesis where I will be looking at quantum correlations established between Alice and Bob with an energy bound on some quantum resource shared between them.

27-Electron-Positron pair generation in spatiotemporaly shaped pulses

• Bernardo Barbosa (GoLP/IPFN - IST)

Positron sources are important both for fundamental science and industrial applications. Generating and accelerating positrons to relativistic energies in a controlled way is a challenge due to many factors (e.g. annihilation, radiation reaction, defocusing, etc.). We are proposing a project that takes advantage of the novel ways of shaping intense laser light to control the positron creation in the laser-electron beam or laser-photon beam scattering.

28-High Temperature Superconductors for Energy Generation

• Maria Mesquita (CeFEMA)

Superconductors' properties make them very attractive for technological applications. However, standard superconductors have critical temperatures much lower than room temperature, requiring the use of expensive cryostats. High temperature superconductors (HTS) are defined for having a critical temperature above 77K, that corresponds to the boiling temperature of liquid nitrogen at atmospheric pressure. Therefore, HTS can be cooled at a much lower cost than standard superconductors. However, simulations of HTS setups are usually performed using an empirical highly non-linear relation between the electric field and the current density, that has not been explained by a consistent theory of superconductivity. Moreover, it renders calculations numerically unstable and extremely time-consuming. The main goal of this thesis is to develop new modelling numerical tools for HTS setups. Besides being compatible with the Ginzburg-Landau theory of superconductivity, they must provide good numerical stability, be scalable and adequate to the current computational resources.

29-Gravitational Waves - A Probe to New Physics

• Ricardo Santos (CFTP and CIDMA)

Despite the tremendous success of the Standard Model (SM) to describe matter and its interactions, we know Beyond the SM (BSM) theories are necessary to solve some of the open problems in physics. The current generation of colliders is not effective in testing such theories. However, gravitational waves (GWs) emitted in the Electroweak Phase Transition may be detected as a stochastic background by upcoming experiments such as LISA. Their spectrum can provide hints of the underlying theory. We covered the relevant concepts of phase transitions and introduced state-of-the-art formulae for the stochastic GW background (SGWB) spectrum. We presented the complex singlet extension of the SM (cxSM). Using the numerical tool, CosmoTransitions, we computed the SGWB spectrum for the simplest case of the cxSM, where the complex singlet does not acquire a vacuum expectation value at $T=0$. We found only weak first-order phase transitions not detectable by LISA. We also addressed concerns regarding numerical instabilities on calculating the Euclidean action. No instabilities were found for the computed phase transition.

30-Effects of Disorder in Higher-order Topological Insulators

• Hugo Lóio (CeFEMA - Instituto Superior Técnico)

Topological insulators are a current hot topic of research due to their remarkable electric properties, such as the existence of quantized robust edge states, promising groundbreaking applications in quantum computing. Higher-order topological insulators (HOTIs) are a new (conceptualized in 2017) type of topological material featuring exciting properties. HOTIs extend the notion of a topological insulator, in the sense that their edge states have lowered dimensionality. Any practical implementation of such systems implies the existence of impurities and defects in the underlying material realization, constituting disorder. Disorder may break the topological properties of systems but may also cause topological transitions to non-trivial topological phases. Determining the effects of disorder in these systems is thus of paramount importance. Although some advancements have been made in this topic, a study of the disordered third-order topological insulator is still lacking, and will therefore be our subject in this master's thesis.

31-The diffusion of information in social media

• Pedro Duarte (LIP | Social Physics and Complexity (SPAC))

In social media platforms, such as Twitter, short messages (tweets) can be copied (re-tweeted) several times giving rise to long cascades. These cascades are not evenly distributed. In fact, they have been shown to have a power-law tail, whereby there are a few, very large cascades, while the majority of tweets are not retweeted at all. In my master thesis, I will study the underlying network structure that gives rise to these dynamics.

32-Can QGP be produced in the interaction of UHECRs with Earth's atmosphere?

• Beatriz Artur (IST)

*Ultra-High Energy Cosmic Rays* interact with the Earth’s atmosphere producing *Extensive Air Shower*s at very high energies, which are not accessible at the LHC. But the data that we have collected over the years from measurements of these air showers shows us an inconsistency in the number of muons, regarding the hadronic models we have been using so far. This is known as the *Muon Puzzle*. Recent experiments with heavy ions at the LHC have unravelled a new state of matter, called *Quark-Gluon Plasma*, which has been studied through models like the EPOS-LHC. However, this model was insufficient and so it was modified in order to phenomenological explain the muon excess that had been observed, originating the *EPOS-QGP*. The goal of this project is to use this new model to assess if quark-gluon plasma can be formed not only at LHC energies but also in the extensive air showers of cosmic rays.

33-Topological Waves in 2D Plasmas

• Alexandru Ciobanu (Instituto Superior Técnico)

We employ topological concepts to study chiral edge modes in two-dimensional plasmas. By approximating the plasma as a fluid we calculate the topological invariant of its Fourier-space bands, which are the dispersion relations of waves in the bulk of the system. Furthermore, calculation of possible wave-forms propagating in a single direction at the boundary of the system allows for a principle of bulk-edge correspondence, where their signed number is fixed by the topology of the bulk. Using various electric potential configurations, we aim to produce protected waves in the terahertz-frequency range.

34-Black Hole Fusion in Alternative Theories of Gravity

• João Dias (Instituto Superior Técnico)

Studying black hole fusion generally requires very powerful computational resources. Using a technique called the Extreme Mass Ratio approach (in which one of the black holes becomes infinite in size) it's possible to simulate black hole fusion in a straightforward manner, namely tracing the event horizon simply by looking at how geodesics (light rays) evolve around the black hole binary. This approach is pursued in the case of a small Schwarzschild black hole. A characterization of the merger is then put forward, in which the duration of the merging event, the evolution of the width of the throat, and the difference between the surface area of the Schwarzschild black hole and its resulting projection in the final horizon are easily computed. Finally, some considerations about the extension of this technique to black hole fusion in alternative theories of gravity (namely Scalar-Tensor-Vector Gravity) is undertaken.

35-Blockchain-based Smart Contracts Application for Energy Trading

• Joana Bugalho (IST/IN+)

The need to restructure the energy markets has become a pressing matter in recent years. As the energy market evolves to integrate more sustainable energy sources, new agents that consume but can also produce energy - the so called prosumers - start to participate in the market. Consequently, the traditional centralized structure solution can no longer support the challenges that the energy market brings today. It becomes crucial to create new business models, decentralized, efficient and running in secure platforms, to support energy interactions within a community such that the use of sustainable energy becomes more affordable and reliable. This project proposes the development of a platform, using a blockchain-based solution, that implements smart contracts that automatically validate and audit energy transitions, contributing in this way to a more sustainable society. Apart from contributing to emissions reduction and energy efficiency, it may also have significant financial impacts, by shielding the market from fossil fuels market instability. Therefore, compared to the systems in place today, we can increase the efficiency, speed, reliability, scalability, and security of the energy markets.

36-Jet substructure tools to identify hadronization timescales

• Nuno Olavo (LIP/IST)

Jets are algorithmic proxies of hard scattered partons, i.e. quarks/gluons, in high energy collisions. The clustering algorithms used in jet measurements contain additional information regarding the jet shower. This work focused on proton-proton collisions and uses the soft-drop algorithm procedure as an additional handle to exploit the jet shower splitting pattern. An analysis of the jet formation time at different splittings inside the jet shower shows promise in the search for the hadronization timescales.