231 research outputs found
Nuclearity and Thermal States in Conformal Field Theory
We introduce a new type of spectral density condition, that we call
L^2-nuclearity. One formulation concerns lowest weight unitary representations
of SL(2,R) and turns out to be equivalent to the existence of characters. A
second formulation concerns inclusions of local observable von Neumann algebras
in Quantum Field Theory. We show the two formulations to agree in chiral
Conformal QFT and, starting from the trace class condition for the semigroup
generated by the conformal Hamiltonian L_0, we infer and naturally estimate the
Buchholz-Wichmann nuclearity condition and the (distal) split property. As a
corollary, if L_0 is log-elliptic, the Buchholz-Junglas set up is realized and
so there exists a beta-KMS state for the translation dynamics on the net of
C*-algebras for every inverse temperature beta>0. We include further
discussions on higher dimensional spacetimes. In particular, we verify that
L^2-nuclearity is satisfied for the scalar, massless Klein-Gordon field.Comment: 37 pages, minor correction
Ubic: Bridging the gap between digital cryptography and the physical world
Advances in computing technology increasingly blur the boundary between the
digital domain and the physical world. Although the research community has
developed a large number of cryptographic primitives and has demonstrated their
usability in all-digital communication, many of them have not yet made their
way into the real world due to usability aspects. We aim to make another step
towards a tighter integration of digital cryptography into real world
interactions. We describe Ubic, a framework that allows users to bridge the gap
between digital cryptography and the physical world. Ubic relies on
head-mounted displays, like Google Glass, resource-friendly computer vision
techniques as well as mathematically sound cryptographic primitives to provide
users with better security and privacy guarantees. The framework covers key
cryptographic primitives, such as secure identification, document verification
using a novel secure physical document format, as well as content hiding. To
make a contribution of practical value, we focused on making Ubic as simple,
easily deployable, and user friendly as possible.Comment: In ESORICS 2014, volume 8712 of Lecture Notes in Computer Science,
pp. 56-75, Wroclaw, Poland, September 7-11, 2014. Springer, Berlin, German
Energy Reduction in Public Building Stock: Assessing the Impact of Control Strategy over Expected Energy Savings and Indoor Comfort Level
peer reviewedIn the framework of EU FP7 BRICKER project, the renovation of public owned nonresidential buildings is addressed through the installation of innovative passive and active technologies. The expected impact is a primary energy reduction of about 50% with respect to the existing scenario with a large replication potential under different European countries.
In order to achieve such ambitious goal one issue that cannot be ignored is the effect of control
strategy, not only over the resulting energy performance but also over the resulting indoor comfort conditions.
In this paper, the actual control strategy implemented in the Belgian demo of Bricker project is introduced, compared against an ideal approach and accordingly optimized. The resulting proposed approach is then tested by means of numerical simulations over a base case scenario
before renovation.
The main conclusion of this work is the demonstration that control strategy of energy generation and distribution systems has to be revised whenever deep renovation of passive or active building technologies is undertaken. Contrarily to which, project renovation goals cannot be met.BRICKER - Total Renovation Strategies for Energy Reduction in Public Building Stock (BRICKER
Scaling algebras and pointlike fields: A nonperturbative approach to renormalization
We present a method of short-distance analysis in quantum field theory that
does not require choosing a renormalization prescription a priori. We set out
from a local net of algebras with associated pointlike quantum fields. The net
has a naturally defined scaling limit in the sense of Buchholz and Verch; we
investigate the effect of this limit on the pointlike fields. Both for the
fields and their operator product expansions, a well-defined limit procedure
can be established. This can always be interpreted in the usual sense of
multiplicative renormalization, where the renormalization factors are
determined by our analysis. We also consider the limits of symmetry actions. In
particular, for suitable limit states, the group of scaling transformations
induces a dilation symmetry in the limit theory.Comment: minor changes and clarifications; as to appear in Commun. Math.
Phys.; 37 page
El cambio global
En este artĂculo se analiza un subconjunto de los fenĂłmenos conocidos como Cambio Global y en los que el autor ha realizado algunas investigaciones. Desde que se originĂł, hace unos cuatro mil seiscientos millones de años (4,6 Ga) hasta el presente, la Tierra ha sido un planeta cambiante. El cambio es producido por enormes fuerzas naturales que elevan montañas, quiebran la corteza terrestre, hacen emerger volcanes que cambian el paisaje geolĂłgico, crean islas y archipiĂ©lagos y otros fenĂłmenos de similar magnitud que, a veces, cambian el clima. La acciĂłn humana es irrelevante ante los cambios producidos por estas fuerzas naturales. Sin embargo, en pequeña escala, acumulativa, la humanidad produce otros cambios que pueden controlarse, evitarse o modificarse. Estos cambios se operan principalmente en la atmĂłsfera y tienen efectos sobre uno o más subsistemas de la Tierra.Universidad Nacional de La Plat
From Operator Algebras to Superconformal Field Theory
We make a review on the recent progress in the operator algebraic approach to
(super)conformal field theory. We discuss representation theory, classification
results, full and boundary conformal field theories, relations to supervertex
operator algebras and Moonshine, connections to subfactor theory and
noncommutative geometry
El cambio global
En este artĂculo se analiza un subconjunto de los fenĂłmenos conocidos como Cambio Global y en los que el autor ha realizado algunas investigaciones. Desde que se originĂł, hace unos cuatro mil seiscientos millones de años (4,6 Ga) hasta el presente, la Tierra ha sido un planeta cambiante. El cambio es producido por enormes fuerzas naturales que elevan montañas, quiebran la corteza terrestre, hacen emerger volcanes que cambian el paisaje geolĂłgico, crean islas y archipiĂ©lagos y otros fenĂłmenos de similar magnitud que, a veces, cambian el clima. La acciĂłn humana es irrelevante ante los cambios producidos por estas fuerzas naturales. Sin embargo, en pequeña escala, acumulativa, la humanidad produce otros cambios que pueden controlarse, evitarse o modificarse. Estos cambios se operan principalmente en la atmĂłsfera y tienen efectos sobre uno o más subsistemas de la Tierra.Universidad Nacional de La Plat
El cambio global
En este artĂculo se analiza un subconjunto de los fenĂłmenos conocidos como Cambio Global y en los que el autor ha realizado algunas investigaciones. Desde que se originĂł, hace unos cuatro mil seiscientos millones de años (4,6 Ga) hasta el presente, la Tierra ha sido un planeta cambiante. El cambio es producido por enormes fuerzas naturales que elevan montañas, quiebran la corteza terrestre, hacen emerger volcanes que cambian el paisaje geolĂłgico, crean islas y archipiĂ©lagos y otros fenĂłmenos de similar magnitud que, a veces, cambian el clima. La acciĂłn humana es irrelevante ante los cambios producidos por estas fuerzas naturales. Sin embargo, en pequeña escala, acumulativa, la humanidad produce otros cambios que pueden controlarse, evitarse o modificarse. Estos cambios se operan principalmente en la atmĂłsfera y tienen efectos sobre uno o más subsistemas de la Tierra.Universidad Nacional de La Plat
GRANVILLE SHARP PATTISON (1791.–1851.): ŠKOTSKI ANATOM I KIRURG SKLON SUKOBIMA
Granville Sharp Pattison was a Scottish anatomist and surgeon who also taught in the United States. This character from the history of anatomy lived a very colourful life. As many are unaware of Pattison, the present review of his life, contributions, and controversies seemed appropriate. Although Pattison was known to be a good anatomist, he will be remembered for his association with a propensity for conflict both in Europe and the United States.Granville Sharp Pattison je škotski anatom i kirurg koji je također podučavao u Sjedinjenim Američkim Državama. Ovaj lik iz povijesti anatomije živio je vrlo šaroliki život. Budući da mnogi nisu upoznati s Pattisonom, ovaj pregled njegova života, doprinosa i kontroverzi čini se prikladnim. Iako je Pattison bio poznat kao dobar anatom, on će biti zapamćen po svojoj povezanosti sa sklonošću sukobima i u Europi i u SAD-u
On the uniqueness of diffeomorphism symmetry in Conformal Field Theory
A Moebius covariant net of von Neumann algebras on S^1 is diffeomorphism
covariant if its Moebius symmetry extends to diffeomorphism symmetry. We prove
that in case the net is either a Virasoro net or any at least 4-regular net
such an extension is unique: the local algebras together with the Moebius
symmetry (equivalently: the local algebras together with the vacuum vector)
completely determine it. We draw the two following conclusions for such
theories. (1) The value of the central charge c is an invariant and hence the
Virasoro nets for different values of c are not isomorphic as Moebius covariant
nets. (2) A vacuum preserving internal symmetry always commutes with the
diffeomorphism symmetries. We further use our result to give a large class of
new examples of nets (even strongly additive ones), which are not
diffeomorphism covariant; i.e. which do not admit an extension of the symmetry
to Diff^+(S^1).Comment: 25 pages, LaTe
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