Leonardo Colletti

Vacancies in quantal Wigner crystals near melting

We estimate the formation energy of lattice vacancies in quantal Wigner crystals of charged particles near their melting point at zero temperature, in terms of the crystalline Lindemann parameter and of the static dielectric function of the fluid phase near freezing. For both two-dimensional (2D) and three-dimensional (3D) crystals of electrons, our results suggest the presence of vacancies in the ground state at the melting density.

OVERTURNING DILTHEY'S VIEW ON NATURAL SCIENCES

Wilhelm Dilthey’s exploration of the scientific status of disciplines such as history, sociology, etc. (which he calls the spiritual sciences) is grounded on a detailed attempt of demarcation between these sciences and the natural sciences. Backbone elements of his categorization are contextualization vs. decontextualization, internal vs. external subject matter, singular vs. universal description, understanding vs. explanation, ethical relevance vs. irrelevance. As a consequence, a long-standing, popular separation between the so-called two cultures found an institutionalization at the academic level. By referring to each of these items, I propose here a collection of arguments towards a perspective in which this separation is not only reduced, but an unification is attempted in an unexpected direction: there are the natural sciences which should fundamentally be seen as spiritual sciences, rather than the opposite. In the long term, a reflection on this may lead to a cultural shift in how natural sciences are perceived, inside and outside academy, and in the methods in which both kind of sciences are explored. L’esplorazione di Wilhelm Dilthey dello statuto di discipline quali storia, sociologia, ecc. (chiamate scienze dello spirito) e fondata su un dettagliato tentativo di demarcazione tra queste scienze e le scienze della natura. Gli elementi portanti di tale categorizzazione sono contestualizzazione o decontestualizzazione, internalita o esternalita dell’oggetto di studio, singolarita o universalita, comprensione o spiegazione, rilevanza o irrilevanza etica. Come conseguenza, e stata istituzionalizzata sul piano accademico quella separazione da molto tempo percepita a livello popolare e detta delle due culture. Facendo riferimento a ciascun elemento, propongo qui una serie di argomenti in favore di una prospettiva non solo di unificazione, ma, se di unificazione si puo parlare, in una direzione inaspettata: sono le scienze naturali che possono essere viste essenzialmente come delle scienze dello spirito, e non viceversa. Sul lungo periodo, una riflessione in tal senso potrebbe portare a uno shift culturale nel modo in cui le scienze delle natura sono percepite, dentro e fuori l’accademia, e nei metodi in cui entrambe le categorie di scienze sono indagate.

Bridging the two cultures

Physics explains our universe with great success, providing us with a working knowledge of reality from atoms to large-scale structures such as stars and galaxies.

COLLECTIVE SPIN STATES IN THE ELECTRON GAS IN DIFFERENT DIMENSIONS AND GEOMETRIES

We study spin longitudinal and transverse linear response of the 3-dimensional electron gas, metal clusters and quantum dots. When the systems are spin unpolarized in the ground state, a low energy collective state emerges in finite size systems due to the discrete shell structure, whereas it is absent in the bulk due to the Landau damping. In the case of spin polarization of the ground state a collective state is present also in the bulk and a family of new collective states appears in finite size systems.