Transcript Bollettino Settimanale 26

Bollettino Settimanale 26-30 settembre 2016
Lun.
AULA MAJORANA ore 11.00 - SEMINARIO TEORICO
Effective quantum dynamics and the arrow of time - a
general survey
J. Frohlich (ETH Zurich)
Il ciclo di seminari e' pensato come un mini-corso introduttivo a una serie di
argomenti avanzati in meccanica quantistica e materia condensata, in
particolare all'effetto Hall quantistico frazionario.
AULA CONVERSI ore 14.30 - SEMINARIO TEORICO INFN
Quantum Theory and Quantum Field theory derived from
information-theoretic principles
Giacomo Mauro D'Adriano
I will review a recent derivation of free quantum field theory from axioms of
information theoretic nature, from countably many systems with interactions
satisfying the requirements of locality, homogeneity, and isotropy. It follows a
theory of quantum cellular automata encompassing a discrete Planck scale,
with maximum value for the Dirac mass (Planck mass) as a consequence of
the unitariety condition, and recovering the usual field theory in the relativistic
limit of small wave-vectors. The theory predicts measurable effects visible in
principle from deep-space high energy events. Special relativity is recovered
from pure quantum, without using space time. The Poincare group is
distorted at Planck scale, and is perfectly recovered for small wave-vectors.
The notion of particle as Poincaré invariant survives. For strong boosts or
large masses also the rest-mass is transformed, leading to a De Sitter
covariance.
We have thus two emerging features with GR flavor: maximum mass and De
Sitter covariance. Very recently the interacting theory has been addressed,
starting with the one-dimensional case which satisfies the locality axiom,
corresponding to an Hubbard Fermionic automaton which is analytically
solved by the Bethe ansatz. Numerical evaluations of the automata will be
shown, and a simple asymptotic analytical approach will be given that allows
to derive a general dispersive Schroedinger equation holding in all regimes
for narrow-band states describing quantum particles.
AULA CONVERSI ore 16.00 - SEMINARIO DI ASTROFISICA
The geometrical nature of the cosmological inflation in the
framework of the Weyl-Dirac conformal gravity theory
Francesco De Martini (Accademia dei Lincei)
The nature of the scalar field responsible for the cosmological inflation, the
inflaton, is found to be rooted in the most fundamental concept of the Weyls
differential geometry: the parallel displacement of vectors in curved spacetime. The Euler-Lagrange theory based on a scalar-tensor Weyl-Dirac
Lagrangian leads straightforwardly to the Einstein equation admitting as a
source the characteristic energy-momentum tensor of the inflaton field. Within
the dynamics of the inflation, e.g. in the slow roll transition from a false toward
a true vacuum, the inflatons geometry implies a temperature driven symmetry
change between a highly symmetrical Weylan to a low symmetry Riemannian
scenario. Since the dynamics of the Weyl curvature scalar, constructed over
differentials of the inflaton field, has been found to account for the quantum
phenomenology at the microscopic scale, the present work suggests
interesting connections between the micro and the macro aspects of our
Universe.
Mar.
Mer.
AULA MAJORANA
ore 11.00
SEMINARIO TEORICO
Effective
quantum
dynamics and the arrow
of time - a general survey
J. Frohlich
(ETH Zurich)
Il ciclo di seminari e' pensato
come un mini-corso introduttivo a
una serie di argomenti avanzati
in meccanica quantistica e
materia
condensata,
in
particolare
all'effetto
Hall
quantistico frazionario.
Gio.
Ven.
AULA MAJORANA ore 11.00
SEMINARIO TEORICO
Bose particles in a box: A convergent expansion of the ground in the mean field limiting regime
A. Dal Pizzo
I shall report on a novel multi-scale technique to study many-body quantum systems where the total number of particles is kept fixed. The
method is based on Feshbach-Schur map and the scales are represented by occupation numbers of particle states. First, I consider a
three-modes (including the zero mode) Bogoliubov Hamiltonian for a sufficiently small ratio between the kinetic energy and the Fourier
component of the (positive type) potential corresponding to the two nonzero modes. For any space dimension d d\geq 1 and in the mean
field limiting regime (i.e., at fixed box volume |\Lambda| and for a number of particles, N, sufficiently large) this method provides the
construction of the ground state and its expansion in terms of the bare operators that in the limit N \to \infty is up to any desired precision. In
space dimension d\geq 3 the method provides similar results for an arbitrarily large (finite) box and a large but fixed particle density \rho;,
i.e., \rho is independent of the size of the box. Then, I'll show how this method can be extended to finitely many modes (i.e., particles in a
finite box, and u.v. cut-off imposed on the two-body potential) interacting according to the complete Hamiltonian in the mean field limiting
regime.
AULA 8 ore 11.00
SEMINARIO DI STRUTTURA DELLA MATERIA
Depletion interaction in binary mixtures of thermoresponsive microgels
Maxime Bergman (Physical Chemistry, Lund University,Lund,Sweden)
Thermoresponsive microgels are intriguing colloids that exhibit a rich phase behavior due to their unique soft potential and swelling
behavior. The thermoresponsive swelling behavior of microgels allows us to use the temperature as an external control to vary the volume
fraction and softness of the particles in situ. Here we report on an investigation of the structural correlations of soft microgels with a radius
R(15°C) = 440 nm in the presence of a second population of small microgels (R(15°C) = 29 nm) through confocal laser scanning
microscopy. We combine this with computer simulations in order to probe the effective interaction potential and the resulting structural
correlations as a function of temperature and concentration. We observe the presence of an additional attraction between the big microgels
due to the depletion effect arising from the addition of small particles. Since the two types of microgels have similar swelling behavior, we
can use temperature to change the effective volume fraction and the softness of the particles, while keeping the size ratio constant. When
compared to the depletion effect caused by small microgels in hard sphere suspensions, the presence of the small particles influences the
radial distribution function (g(r)) of the large microgels very differently: instead of a pronounced peak increase (indicative of attraction, seen
for hard spheres), the microgels show smaller center-to-center distances but no significant peak increase. We discuss our findings in view
of the particular internal core shell architecture of the microgels, and their ability to de-swell, deform and/or interpenetrate.
AULA MAJORANA ore 14.30
SEMINARIO TEORICO INFN
KL → π0νν Beyond Grossman-Nir Bound
George Wei-Shu Hou (Taiwan University)
Due to different predicaments for K+ → π+νν vs KL → π0νν detection, a fallacy has persisted in the perceived Grossman-Nir bound on KL
→ π0νν search, which only the 2015 data of KOTO experiment can reach and hopefully breach. We point out this loophole, that KL →
π0X0, where X0 is some missing energy object with missing mass similar to the pion, can be above the GN bound. An existence proof is
given for a model with a gauged Lµ – Lτ symmetry, with vector-like quarks that link with SM quarks which induce KL → π0Z′ decay. The
model illustrates the potential impact of the discovery of KL → π0X0, which could happen in the next few years.
AULA CONVERSI ore 15.00
SEMINARIO DI ASTROFISICA
Observing the polarized sky with Advanced ACTPol
Maria Salatino (Princeton University, NJ, US)
Imagine of building a bolometric camera, sensitive to polarization, housing 2000 Transition Edge Sensors, sensitive to two frequency bands
centered at 150 and 220 GHz, cooled down to 0.1K. How it would look like? What do you think would be the challenging aspects? Now.
Imagine this camera at the focus of a 6 meter telescope in the Atacama desert, in Northern Chile. What do you think would be the science
targets of this camera? I will walk with the audience through these, and many more, questions, presenting Advanced ACTPol, the new
bolometric camera of the Atacama Cosmology Telescope.