6 research outputs found
Symmetries, Holography and Quantum Phase Transition in Two-dimensional Dilaton AdS Gravity
We present a revisitation of the Almheiri-Polchinski dilaton gravity model
from a two-dimensional (2D) bulk perspective. We describe a peculiar feature of
the model, namely the pattern of conformal symmetry breaking using bulk Killing
vectors, a covariant definition of mass and the flow between different vacua of
the theory. We show that the effect of the symmetry breaking is both the
generation of an infrared scale (a mass gap) and to make local the Goldstone
modes associated with the asymptotic symmetries of the 2D spacetime. In this
way a non vanishing central charge is generated in the dual conformal theory,
which accounts for the microscopic entropy of the 2D black hole. The use of
covariant mass allows to compare energetically the two different vacua of the
theory and to show that at zero temperature the vacuum with a constant dilaton
is energetically preferred. We also translate in the bulk language several
features of the dual CFT discussed by Maldacena et al. The uplifting of the 2D
model to dimensional theories exhibiting hyperscaling violation is
briefly discussed.Comment: 7 pages, no figure
Dark Energy from holographic theories with hyperscaling violation
We show that analytical continuation maps scalar solitonic solutions of
Einstein-scalar gravity, interpolating between an hyperscaling violating and an
Anti de Sitter (AdS) region, in flat FLRW cosmological solutions sourced by a
scalar field. We generate in this way exact FLRW solutions that can be used to
model cosmological evolution driven by dark energy (a quintessence field) and
usual matter. In absence of matter, the flow from the hyperscaling violating
regime to the conformal AdS fixed point in holographic models corresponds to
cosmological evolution from power-law expansion at early cosmic times to a de
Sitter (dS) stable fixed point at late times. In presence of matter, we have a
scaling regime at early times, followed by an intermediate regime in which dark
energy tracks matter. At late times the solution exits the scaling regime with
a sharp transition to a dS spacetime. The phase transition between hyperscaling
violation and conformal fixed point observed in holographic gravity has a
cosmological counterpart in the transition between a scaling era and a dS era
dominated by the energy of the vacuum.Comment: 18 pages, 4 figures. V2:Some typo errors and Eq. (3.12) corrected,
three references adde
Elemental fingerprinting combined with machine learning techniques as a powerful tool for geographical discrimination of honeys from nearby regions
Discrimination of honey based on geographical origin is a common fraudulent practice and is one of the most investigated topics in honey authentication. This research aims to discriminate honeys according to their geographical origin by combining elemental fingerprinting with machine-learning techniques. In particular, the main objective of this study is to distinguish the origin of unifloral and multifloral honeys produced in neighboring regions, such as Sardinia (Italy) and Spain. The elemental compositions of 247 honeys were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The origins of honey were differentiated using Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and Random Forest (RF). Compared to LDA, RF demonstrated greater stability and better classification performance. The best classification was based on geographical origin, achieving 90% accuracy using Na, Mg, Mn, Sr, Zn, Ce, Nd, Eu, and Tb as predictors
Elemental Fingerprinting Combined with Machine Learning Techniques as a Powerful Tool for Geographical Discrimination of Honeys from Nearby Regions
Discrimination of honey based on geographical origin is a common fraudulent practice and is one of the most investigated topics in honey authentication. This research aims to discriminate honeys according to their geographical origin by combining elemental fingerprinting with machinelearning techniques. In particular, the main objective of this study is to distinguish the origin of unifloral and multifloral honeys produced in neighboring regions, such as Sardinia (Italy) and Spain. The elemental compositions of 247 honeys were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The origins of honey were differentiated using Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and Random Forest (RF). Compared to LDA, RF demonstrated greater stability and better classification performance. The best classification was based on geographical origin, achieving 90% accuracy using Na, Mg, Mn, Sr, Zn, Ce, Nd, Eu, and Tb as predictor