Spinning Loop Black Holes

In this paper we construct four Kerr-like spacetimes starting from the loop black hole Schwarzschild solutions (LBH) and applying the Newman-Janis transformation. In previous papers the Schwarzschild LBH was obtained replacing the Ashtekar connection with holonomies on a particular graph in a minisuperspace approximation which describes the black hole interior. Starting from this solution, we use a Newman-Janis transformation and we specialize to two different and natural complexifications inspired from the complexifications of the Schwarzschild and Reissner-Nordstrom metrics. We show explicitly that the space-times obtained in this way are singularity free and thus there are no naked singularities. We show that the transformation move, if any, the causality violating regions of the Kerr metric far from r=0. We study the space-time structure with particular attention to the horizons shape. We conclude the paper with a discussion on a regular Reissner-Nordstrom black hole derived from the Schwarzschild LBH and then applying again the Newmann-Janis transformation.Comment: 18 pages, 18 figure

Hawking emission from quantum gravity black holes

We address the issue of modelling quantum gravity effects in the evaporation of higher dimensional black holes in order to go beyond the usual semi-classical approximation. After reviewing the existing six families of quantum gravity corrected black hole geometries, we focus our work on non-commutative geometry inspired black holes, which encode model independent characteristics, are unaffected by the quantum back reaction and have an analytical form compact enough for numerical simulations. We consider the higher dimensional, spherically symmetric case and we proceed with a complete analysis of the brane/bulk emission for scalar fields. The key feature which makes the evaporation of non-commutative black holes so peculiar is the possibility of having a maximum temperature. Contrary to what happens with classical Schwarzschild black holes, the emission is dominated by low frequency field modes on the brane. This is a distinctive and potentially testable signature which might disclose further features about the nature of quantum gravity.Comment: 36 pages, 18 figures, v2: updated reference list, minor corrections, version matching that published on JHE

A non commutative model for a mini black hole

We analyze the static and spherically symmetric perfect fluid solutions of Einstein field equations inspired by the non commutative geometry. In the framework of the non commutative geometry this solution is interpreted as a mini black hole which has the Schwarzschild geometry outside the event horizon, but whose standard central singularity is replaced by a self-gravitating droplet. The energy-momentum tensor of the droplet is of the anisotropic fluid obeying a nonlocal equation of state. The radius of the droplet is finite and the pressure, which gives rise to the hydrostatic equilibrium, is positive definite in the interior.Comment: 10 pages, 2 figures, bibliography enlarged, reference in the conclusion fixed, some typos correcte

Paesaggi di rovine. Paesaggi rovinati. Landscape of Ruins. Ruined Landscapes

Il libro ha come oggetto lo studio dei paesaggi storici e la loro integrazione in aree o regioni metropolitane. Il tema di riflessione è oggetto di un recente documento dell’UNESCO che ha definito il concetto di “Paesaggio storico urbano”, uno strumento che pone al centro il paesaggio al fine di proteggere il vulnerabile patrimonio storico e naturale dei nostri territori, integrando strategie di tutela, di pianificazione e interventi contemporanei. In questo quadro, il ruolo delle comunità accademiche è considerato centrale e vengono incoraggiate ricerche che adottino il concetto di “Paesaggio Storico Urbano” per studiare, secondo una metodologia integrata i territori metropolitani. Questi argomenti non sono nati adesso. Gli studi della struttura e della storia delle città sono un primario esito della cultura urbana italiana, sia per le discipline architettoniche sia per le scienze archeologiche basti pensare ai contributi di Rodolfo Lanciani, Saverio Muratori, Aldo Rossi. Tuttavia, lavorare nei processi di trasformazione in modo sinergico, non è a tutt’oggi una pratica consolidata in Italia. S’incontrano molti irrigidimenti su posizioni disciplinari. Nonostante la contemporaneità abbia affermato il passaggio da una cultura che si occupava di “oggetti” a una scienza delle relazioni, gli specialismi e il frazionamento dei saperi finiscono per prevalere, causando gravi e dannosi ritardi. Nella maggior parte dei casi, le aree archeologiche, indicate nella cartografia come zone urbane vincolate, finiscono per essere definitivamente separate dal contesto e dal patrimonio urbano, cui pur sempre appartengono. Sono ormai alcuni decenni che la cultura architettonica ha denunciato l'inadeguatezza dello zoning come strumento per la pianificazione delle città, riconoscendo che la suddivisione del suolo in aree omogenee e monofunzionali è espressione di una concezione sommatoria e analitica, incapace di raffigurare le molteplici relazioni necessarie a “fare città”. L’Italia è disseminata di paesaggi in cui il rapporto tra archeologia, spazio urbano, aree agricole, rappresenta terreno materiale e concettuale per possibili sinergie. Se non dobbiamo guardare al classico come morta eredità, ma come qualcosa da riconquistare ogni giorno, le rovine possono rappresentare un punto di partenza per definire nuovi valori relazionali, fondati sul riconoscimento di appartenenze e avvalorati dalla condizione di potere fare parte simultaneamente dei processi culturali ed economici del passato e della contemporaneità. Il volume raccoglie testi che trattano del rapporto tra aree archeologiche e contesti urbani. I contributi rilevano le numerose aporie e rigidità ancora presenti in Italia, che ostacolano uno sguardo trasversale e integrato e forniscono un quadro teorico di riferimento, che è stato utile per esplorare quattro casi-studio (che sono oggetto di specifiche pubblicazioni work in progress) su i quali operare proposte di ri-significazioni dei luoghi: il Parco dell’Appia Antica, il Parco dei Campi Flegrei, la Magna Grecia e il Parco della villa del Casale e del fiume Gela. Cinque diverse sezioni del volume - Tutela e Re-invenzione, Margini e Marginalità, Territorializzazioni, Ri-significare i luoghi e Architettura per i paesaggi archeologici rispondono secondo diversi punti di vista al tema di come restituire alle tracce del passato un ruolo nell’immaginario culturale urbano della città contemporanea. L’Atlante dei paesaggi archeologici fornisce, attraverso una selezione di progetti significativi, ulteriori possibili risposte al tema.The book has as its object the study of historic landscapes and their integration in metropolitan areas or regions. The theme is the subject of a recent UNESCO document that has defined the concept of "Historic Urban Landscape", a notion that focuses on the landscape in order to protect the vulnerable natural and historical heritage of our territories, integrating strategies of protection, planning and design interventions. In this context, the role of the academic community is considered crucial and are encouraged researches that adopt the UNESCO concept of "Historic Urban Landscape" to study, according to an integrated methodology, the metropolitan territories. Studies of the structure and the history of the city are a primary outcome of the Italian urban culture, both for the architectural disciplines and for the archaeological sciences: enough to think of the contributions of Rodolfo Lanciani, Saverio Muratori, Aldo Rossi. However, working in the transformation processes in a synergistic way, it is not at all, today, an established practice in Italy. We meet a stiffening attitude on disciplinary positions. Although the contemporary era set the transition from a culture that dealt with “objects” to a culture of relationships, specializations and the fragmentation of knowledge prevail, ending up causing serious and harmful cultural delays. In most cases, the archaeological areas, as indicated in urban plans are protected areas that end up being permanently separated from the environment to which they belong. Several decades ago the architectural culture has denounced the inadequacy of zoning as a tool for city planning, recognizing that the division of the land into homogeneous and single-purpose areas is the expression of an analytical concept, unable to portray the many relationships necessary to "make the city". Italy is a landscape in which the relationship between archaeology, urban space and agricultural areas is a material and conceptual ground for possible synergies. If we should not look to the our classic past as dead heritage, but as something to renew every day, ruins can be a starting point to define new relational values, founded on the recognition of identities and belonging simultaneously to the past and the present. The book contains texts dealing with the relationship between archaeological sites and urban contexts. The contributions reveal the many aporias and rigidities still present in Italy, which hinder an integrated look and provide a theoretical framework, which was useful to explore the four selected case studies (which are the subject of specific publications that are work in progress): the Appia Antica Park, the Park of the Campi Flegrei, the Greeks, and the Park of the Villa del Casale and the river Gela. Five different sections of the book - Preservation and Re-invention, Margins and Marginality, Territorializations, Re-defining places and Architecture for Archaeological landscapes – respond, according to different points of view, to the issue of how to return to the traces of the past a role in the imaginary of the contemporary city. The Atlas of archaeological landscapes provides, through a selection of significant projects, other possible responses to the issue. The book is the first outcome of a Research Programs of National Interest (Grant 2009) entitled "Archaeological Landscapes, regions and metropolitan cities. Strategies of the contemporary urban project for the preservation and transformation." The multidisciplinary research team, led by Alessandra Capuano and formed by architects and archaeologists of 4 universities and 5 departments, worked on sites in Rome, Naples, along the Ionian coast of Calabria and Piazza Armerina, strongly characterized historically and symbolically. These areas are mainly regional parks and protected natural areas that often suffer of being partially derelict and semi-abandoned, not well integrated in the urban environment of belonging, with security problems and difficulties to preserve and make accessible the myriad of archaeological fragments and cultural heritage. To ponder on these places was necessary to discuss the vision that we have today of these realities. Thus this first volume (of five) collects the theoretical phase of the investigation that was elaborated through 5 seminars, conducted by the research units (Principal Investigators: Barbanera, Capuano, Miano, Nigrelli, Sestito). Topics were jointly identified, and tried to respond to some different questions. The main thesis was that the archaeological project and urban project could draw support from each other, interacting in the heart of the transformational processes. Italy boasts a complex of laws for the preservation of cultural heritage and landscape that are among the most advanced in the world. However the complicate legislation and the segmentation of skills ends up creating paradoxes and negative effects on the landscape and the cities. Which corrective actions we need to introduce? The protection applies to tangible heritage itself, but what about its role in the urban context and its significance in the public space? It is enough to entrust the maintenance of cultural heritage only to the restoration processes and to the management of the Landmark institution in charge, excluding the “object” from its urban context and the chances of a collective life? Wouldn't be necessary to address an argument concerning the potentials for urban regeneration and for maintaining alive the heritage that social dynamics may introduce? The relationship between architecture and archaeology has been quite investigated in recent years, while less explored is the relationship between the urban context (or landscape) and archaeological areas. The research has focused on this specific issue and has collected best practices useful to ponder on the relationship between archaeological sites and cities. Specific diagrams and plans were drawn to comparably illustrate different international cases selected for the Atlas. Scholars and experts attended seminars not only from Italy, but also from Spain, the United Kingdom, Slovenia, Greece and Lebanon, countries in which the debate on the role of history and heritage has been addressed at the urban scale and the topic is of great interest in the cultural context of those countries. Alessandra Capuano has coordinated the research groups of the five departments and has conducted the research on the case study of the Appia Antica Park. In addition to having edited the whole publication of which has responsibility for the overall scientific direction (while the responsibility of each section was in charge of each research unit), she wrote the introductory essay (Introduction pp.10-21), she also edited the scientific selection of the essays regarding the section "Preservation and Re-invention", she wrote the text “Archaeology and New Imaginary” (pp. 37-49) and directed the construction of the Atlas. The book was launched at the National Museum of Rome in Palazzo Altemps by architect Franco Purini and by archaeologist Andreina Ricci and reviews are in program. The research discussed in this book is part of a series of studies on which Alessandra Capuano and the LaGraTe (the laboratory of the department which she directs) have been working for years to address issues that relate to the architecture and the city in its multiple manifestations (the relationship between heritage and new city, contemporary landscapes of the peri-urban, infrastructures and in-between spaces, rural landscapes) https://web.uniroma1.it/lagrate