martedì 26 febbraio 2008

John Baez ...Una miniera di informazioni...

John Baez è uno dei più apprezzati fisici matematici moderni dell'Università della California Riverside, (si è parente della più famosa Joan). I suoi poliedrici interessi vanno dalla matematica pura, alla topologia più avanzata , dalla Teoria Quantistica dei Campi, alla Gravità Quantistica e le Stringhe. Ha scritto uno dei più autorevoli testi sull'interconnessione tra queste discipline di ricerca ("Knots and Quantum Gravity").
Il suo BLOG personale dell'università è una miniera di informazioni presiose, per gli esperti e gli studenti. Vi consiglio di cominciare a conoscere John Baez da questa pagina del suo blog This Week's Finds in Mathematical Physics (Week 260). Non ve ne pentirete!
A presto.

lunedì 25 febbraio 2008

P.A.M. Dirac, Quantum Theory of Electron

P. A. M. Dirac

Dirac has been one of the master of Quantum Theory. The equation which bear his name is the starting point for every theory of quantum matter. In 1928, after the basis of Quantum Mechanics were well established, he wrote a fascinating paper
on the theory of electrons described by a relatively simple spinorial equation.
It explained much of the strange spectroscopic behavior of the matter then known.
It was a profound success in the physics of every time.
Here you can find the original scanned paper, and my personal italian translation.


Emmy Noether Theorem

I have made an italian translation of the famous paper by Emmy Noether on group transformations and conservation laws. Any student in physics knows how much important is for the modern physics the concept of symmetry of a physical systems. Here you can get a free copy of the english or italian version of this memorable article.

Number Theory and Physics

In the last years, a new interest in merging scientific knowledge from different disciplines, has come up. For examples a very interesting thing are the emerging connections between Quantum Mechanics and Consciousness, and biology in general.
More strange are the connections between two such fields as Number Theory and Physics. Loosely speaking, number theory (NT) can be viewed as a big game where the starting rule is: given two symbols 0 and 1 and some algebraic operations (+,*,...), we can build, for example, all the natural numbers n. The scope of the game is to find regular structures, connections, theorems,... arising in this game. Prime Numbers are the most fascinating of such structures, and some of the facts about such numbers are still a mystery (one for all, Riemann Hypothesis). However what have this numbers, and other facts about NT, have in common with Physics?
Well, if you are interested in such questions, the best place on the web to begin with is Matthew Watkin's web site, a very funny place.

Encryption Security

Lest We Remember: Cold Boot Attacks on Encryption Keys

J. Alex Halderman, Seth D. Schoen, Nadia Heninger, William Clarkson, William Paul, Joseph A. Calandrino, Ariel J. Feldman, Jacob Appelbaum, and Edward W. Felten

Abstract Contrary to popular assumption, DRAMs used in most modern computers retain their contents for seconds to minutes after power is lost, even at operating temperatures and even if removed from a motherboard. Although DRAMs become less reliable when they are not refreshed, they are not immediately erased, and their contents persist sufficiently for malicious (or forensic) acquisition of usable full-system memory images. We show that this phenomenon limits the ability of an operating system to protect cryptographic key material from an attacker with physical access. We use cold reboots to mount attacks on popular disk encryption systems — BitLocker, FileVault, dm-crypt, and TrueCrypt — using no special devices or materials. We experimentally characterize the extent and predictability of memory remanence and report that remanence times can be increased dramatically with simple techniques. We offer new algorithms for finding cryptographic keys in memory images and for correcting errors caused by bit decay. Though we discuss several strategies for partially mitigating these risks, we know of no simple remedy that would eliminate them.