Small clusters Renormalization Group in 2D and 3D Ising and BEG models with ferro, antiferro and quenched disordered magnetic interactions

The Ising and BEG models critical behavior is analyzed in 2D and 3D by means of a renormalization group scheme on small clusters made of a few lattice cells. Different kinds of cells are proposed for both ordered and disordered model cases. In particular, cells preserving a possible antiferromagnetic ordering under decimation allow for the determination of the N\'eel critical point and its scaling indices. These also provide more reliable estimates of the Curie fixed point than those obtained using cells preserving only the ferromagnetic ordering. In all studied dimensions, the present procedure does not yield the strong disorder critical point corresponding to the transition to the spin-glass phase. This limitation is thoroughly analyzed and motivated.Comment: 14 pages, 12 figure

The Complex Spherical 2+4 Spin Glass: a Model for Nonlinear Optics in Random Media

A disordered mean field model for multimode laser in open and irregular cavities is proposed and discussed within the replica analysis. The model includes the dynamics of the mode intensity and accounts also for the possible presence of a linear coupling between the modes, due, e.g., to the leakages from an open cavity. The complete phase diagram, in terms of disorder strength, source pumping and non-linearity, consists of four different optical regimes: incoherent fluorescence, standard mode locking, random lasing and the novel spontaneous phase locking. A replica symmetry breaking phase transition is predicted at the random lasing threshold. For a high enough strength of non-linearity, a whole region with nonvanishing complexity anticipates the transition, and the light modes in the disordered medium display typical discontinuous glassy behavior, i.e., the photonic glass has a multitude of metastable states that corresponds to different mode-locking processes in random lasers. The lasing regime is still present for very open cavities, though the transition becomes continuous at the lasing threshold.Comment: 26 pages, 13 figure

Development of new green strategies based on Brønsted and Lewis acid catalysis in organic synthesis

Environmental protection is one of the greatest themes of the XXI century. For what concerns chemistry, in the early 1990’s, even before its current formal and exhaustive definition, given by Paul T. Anastas and John C. Warner in 1998, the term "green chemistry" starts to appear in the literature. Anastas and Warner formulated a list of 12 principles, that constitute the most complete definition of green chemistry. Herein, an effort towards the fulfillment of these principles is presented with respect to: 1) the development of a catalytic system based on hydrate ferric sulfate for the hydration of internal alkynes; 2) an approach to the synthesis of a new family of chiral phosphates for organocatalysis

General phase-diagram of multimodal ordered and disordered lasers in closed and open cavities

We present a unified approach to the theory of multimodal laser cavities including a variable amount of structural disorder. A general mean-field theory is studied for waves in media with variable non-linearity and randomness. Phase diagrams are reported in terms of optical power, degree of disorder and degree of non-linearity, tuning between closed and open cavity scenario's. In the thermodynamic limit of infinitely many modes the theory predicts four distinct regimes: a continuous wave behavior for low power, a standard mode-locking laser regime for high power and weak disorder, a random laser for high pumped power and large disorder and an intermediate regime of phase locking occurring in presence of disorder below the lasing threshold.Comment: 9 pages, 3 figure

The making of smart cities : borders, security and value in New Town Kolkata and Cape Town

The making of smart cities transforms not only infrastructures and practices but also the techniques of urban government and security, and economic processes. This thesis draws on analysis conducted in two research sites: Cape Town, in South Africa and New Town Rajarhat, a satellite township on the outskirts of Kolkata, to present three key arguments. Firstly, and as opposed to mainstream narratives that describe smart cities as seamlessly connected environments, this thesis suggests that urban digitalisation is linked to bordering processes. Whereas critical literature has comprehensively discussed the political implications and risks associated with smart city projects, such as corporatisation and technocratic governance, the specific relations between digital infrastructures and borders, within the urban space, have not yet been discussed. Secondly, this thesis argues that smart cities are inherently security projects, insofar as the deployment of a computing infrastructure of sensing initiates a preemptive apparatus. In security systems, such as the Emergency Policing and Incident Command (EPIC) program in Cape Town, or the Xpresso software for social media monitoring in New Town, algorithms are continuously modelling and acting upon future scenarios; from traffic jams to wildfires, from crime hotspots to citizens’ moods. My third argument is that the computing apparatus of security also serves as an infrastructure of value extraction. Recently, there has been much theorising and debate about security platforms’ economic operations, but the situated modalities in which they extract value from the urban environment remain to be examined. Overall, this thesis points to the socio-spatial, governmental and economic relations that computing infrastructures are generating, or reconfiguring, in the urban environment. These relations articulate distinct processes, including the hierarchisation and control of the urban space, preemptive policies and extractive strategies. Critically analysing these processes allows the registration of the political implications of smart city projects

The King and The Chariot

The King and The Chariot is at its heart, a compilation of all that inspires me in music. From hymn tunes, declamatory fanfares, gentle chorales, and somber laments. For this reason, I chose to write this piece for wind ensemble, since much of the music I’m inspired by is written for that idiom. Most of the piece is based around the hymn, A Mighty Fortress is our God. The hymn itself is primarily presented in a minor mode and in fragments, somewhat reflecting my own personal struggles with Christian spirituality and faith. While most arrangements of A Mighty Fortress are written in a way to be uplifting, I did not aim to do that with this composition. I wanted to write something that sounded darker and deeper, with an ancient feel. I drew heavy inspiration from the music of the medieval and renaissance periods in order to achieve that sound. While there are sections that are more positive in nature, the overall mood is supposed to be dark. The form of the piece was initially meant to be variations on a theme, but during the compositional process it started to become something else. It grew into something similar to an organ improvisation that would function as a postlude or prelude for a Christian mass. Up until recently, this piece was titled Fanfare for Band. At the suggestion of Dr.Silverman, I decided to find a title that better suited the piece. I asked some of my friends for their suggestions, and one of them remarked that the music reminded them of a tarot card that depicted an emperor riding inside a chariot. Due to the processional and regal nature of the music, I thought “The King and The Chariot” would be a fitting title

Regularization and decimation pseudolikelihood approaches to statistical inference in XYXY-spin models

We implement a pseudolikelyhood approach with l2-regularization as well as the recently introduced pseudolikelihood with decimation procedure to the inverse problem in continuous spin models on arbitrary networks, with arbitrarily disordered couplings. Performances of the approaches are tested against data produced by Monte Carlo numerical simulations and compared also from previously studied fully-connected mean-field-based inference techniques. The results clearly show that the best network reconstruction is obtained through the decimation scheme, that also allows to dwell the inference down to lower temperature regimes. Possible applications to phasor models for light propagation in random media are proposed and discussed.Comment: 10 pages, 12 figure