Dinamica pulsurilor laser accelerate in plasma
Raport de faza pentru proiectul Nucleu
Prof. Marian Apostol
IFIN-HH/DFT
The propagation of electromagnetic pulses in plasma is analyzed, especially in connection with electrons accelerated by laser beams in rarefied gaseous plasmas. The interaction of the electromagnetic field with matter is introduced by using the polarization (displacement) field and supplementing Maxwell's equations with the equation of motion of this displacement field. This treatment amounts to using the Lorentz-Drude (plasma) model of polarizable (non-magnetic) matter and provides a solution of the electromagnetic field equations in matter. The plasmon and polariton eigenmodes of electromagnetic field-matter interaction are obtained. The extinction theorem is discussed and its implications in this context are presented, especially in connection with propagation, diffraction and refraction of electromagnetic waves in matter. The construction of a wavepacket and a pulse of electromagnetic field is described and the propagation of the polaritonic pulse in plasma is derived. The typical characteristics of a pulsed polariton, like velocity, transported charge, intensity, electromagnetic and mechanical energy are estimated for the favourable conditions of a rarefied plasma.
Descrierea sistemelor de particule in interactie ca gaze ideale si
modele de defecte dinamice in solide
Dragos Anghel
IFIN-HH - DFT
Voi prezenta o metoda de descriere a sistemelor de particule in interactie ca gaze ideale de statistica fractionara.
Voi prezenta un model pentru descrierea defectelor dinamice in solide vitroase si voi propune o metoda microscopica pentru verificarea validitatii acestui model, precum si a altor modele din literatura (lucru in desfasurare).
Energia Fragmentelor de Fisiune
Raport de faza contract PN-II-ID-PCE-2011-3-0068
Dr. Mihai Mirea
IFIN-HH/DFT
Se determina partitia energiei de excitare a fragmentelor pentru fisiunea rece. Se realizeaza calcule microscopice si dinamice bazate pe ecutiile de imperechere dependente de timp.
On the geometry of Q4 mapping
Stefan Carstea
IFIN-HH, DFT
We discuss singularity structure and deautonomisation of the (p,q) reduction of Q4 lattice equation (discrete Krichever-Novikov). It is shown that its action can be lifted to an automorphism of a rational elliptic surface of A_1^{(1)} type which change the singular fibers. As a result conservation laws are also obtained.
Do we need Feynman diagrams for higher order perturbation theory?
Renata Jora
DFT/IFIN-HH
We compute the three loop beta function for Yang-Mills theories in a novel functional approach which uses the background gauge field as the only source present in the theory. No two or three loop Feynman diagrams are considered in the process.
Quantitative Conditioning Criteria in Bayesian Automatic Adaptive Quadrature
Gheorghe Adam
DFT IFIN-HH
Quantitative criteria enabling Bayesian inferences on the integrand conditioning over monotonicity intervals defined on integrand profiles obtained within the process of building the subrange binary tree associated to the numerical solution of a Riemann integral by automatic adaptive quadrature are derived. The theoretically obtained admissible relative variation bounds of the first order divided differences of the integrand around an abscissa belonging to the monotonicity interval put on firm ground previously reported empirical results.
Perturbative expansion improved by renormalization-group and Borel summation for the QCD Adler function
Irinel Caprini
IFIN-HH, DFT
The QCD Adler function plays a crucial role in the extraction of the strong coupling $\alpha_s$ from the hadronic decay width of the $\tau$ lepton. I discuss the ambiguities of the perturbation expansion of the Adler function and define an improved class of expansions, based on the simultaneous renormalization-group summation and the analytic continuation in the Borel plane. The results are of interest for a precise determination of αs at the scale of Mτ.
Nuclear first order phase transition in heavy-ion reactions at
intermediate energies
Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear
Research, 141980 Dubna, Russian Federation
The nuclear first order phase transition of the liquid-gas type associated with the Gibbs free energy and one associated with the Helmholtz free energy were studied. The main thermodynamical properties of the first order phase transition associated with the Gibbs free energy were explored in the framework of the relativistic mean-field hadronic model. However, the first order phase transition associated with the Helmholtz free energy was investigated in the model of the decay of nuclei into nucleons. The inequivalence of the Laplace and Legendre transforms for the nuclear first order phase transition was revealed. Some results of the quantum statistical multifragmentation model are presented.
Fenomene cooperative noi dintre:
- radiatori cu tranzitii ne-echidistante in interactii neliniare;
- fotonii a doua si mai multe moduri de cavitate optica.
Prof. Nicolae Enache
Institutul de Fizica Aplicata al Academiei de Stiinte a Moldovei
Se propune o noua modalitate de cooperare a trei si mai multi radiatori (nuclee, atomi, molecule) la rezonanta bi-cuantica. De asemenea se propun noi modalitati de cooperare dintre bi-bosonii a doua moduri de cavitate la imprastierea Raman si hiper-Raman.
TeV range black holes formation and decay in different extra-dimenssional scenarios will be discussed. Depending on the scenario it is possible for the micro black holes to be created and decay instantaneously, but also to have very long life times. An overview of the state of the art for ongoing micro black holes searches followed by several proposals for future searches will constitute the second half of the talk.
Institute for Quantum Computing, University of Waterloo
Ontario, Canada
Gedankenexperiments au jucat un rol crucial in fundatiile mecanicii cuantice -- un exemplu celebru este disputa intre Einstein si Bohr. Voi discuta un rezultat recent legat de experimentul delayed-choice (propus de Wheeler) si extensia lui intr-un cadru cuantic. Mai precis, folosirea unui element de control cuantic are mai multe consecinte. In primul rand, ne permite sa masuram fenomene complementare cu un singur setup experimental, conducandu-ne la o reformulare/reinterpretare a principiului complementaritatii al lui Bohr. In al doilea rand, ne permite sa eliminam teorii cu variabile ascunse in care conceptele de "particula" si "unda" sunt proprietati realistice. In sfarsit, ne arata ca o particula cuantica (de ex, un foton) poate avea o comportare de tip morphing intre particula si unda si in anumite conditii poate fi intr-o superpozitie a celor doua stari.
Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH) 30 Reactorului,
Magurele-Bucharest 077125, Romania
Goryachev-Chaplygin, Kovalevskaya, and Brdicka-Eardley-Nappi-Witten pp-waves spacetimes with higher rank Stackel-Killing tensors
Cristina Rugina, IFIN-HH
Thermally generated long-lived correlations in cavity QED
Dr. Vitalie Eremeev, Pontificia Universidad Catolica de Chile, Chile
Rezumat:
A theoretical model for driving a two-qubit system to a stable long-lived entanglement is discussed. The system consists in two atoms, each one coupled to a separate cavity, with the cavities connected by a fiber. The cavity and fiber exchange energy with their individual thermal environment. We found that stable long-lived quantum correlations are generated in the presence of thermal excitations of the environments [V. Eremeev, V. Montenegro, and M. Orszag, Phys. Rev. A 85, 032315 (2012)].
Are we seeing the beginnings of Inflation?
Phantom Cosmology provides an unique opportunity to ``connect'' the phantom driven (low energy meV scale) dark energy phase to the (high energy GUT scale) inflationary era. This is possible because the energy density increases in phantom cosmology. I will present a concrete model where the energy density, but not the scale factor, cycles through phases of standard radiation/matter domination followed by dark energy/inflationary phases, with the pattern repeating itself. An interesting feature of the model is that once we include interactions between the ``phantom fluid'' and ordinary matter, the Big rip singularity is avoided with the phantom phase naturally giving way to a near exponential inflationary expansion ( C. Ilie, T. Biswas, K. Freese, Phys. Rev. D80, 103521).
Nanomagnetism: aspecte actuale si o privire critica asupra adaptabilitatii modelelor teoretice la complexitatea experimentala
Dr. Victor Kuncser, INFM
Se vor prezenta cateva aspecte actuale legate de magnetismul structurilor nanometrice si potentialul lor aplicativ. Se va pune accentual pe problematici legate de magnetismul sistemelor de nanoparticule si pe cele legate de interactiile interfaciale in structuri de multipaturi magnetice cu anizotropii diferite. Se vor discuta critic, din punctul de vedere al experimentatorului, probleme legate de posibilitatile de aplicare ale modelelor teoretice generale la cazurile reale, deosebit de complexe si se vor face observatiii asupra limitelor si contextului in care anumiti parametrii teoretici pot fi corect comparati cu parametrii obtinuti experimental. Se vor mentiona cateva cazuri legate de neconcordanta principiala intre marimea teoretica si marimea experimentala asociata acesteia, relativitatea marimii experimentale fata de metoda de masura utilizata si fata de fenomenul definit precum si a limitelor modelului teoretic in a tine cont de toti parametrii implicati in fenomenul studiat (distributii de defecte/dimensiune/compozitie/faza).
Molecular polarizability near metal surfaces
Cristian-Mihail Teodorescu, National Institute of Materials Physics
A basic electrostatic mechanism (image dipoles)will be proposed, yielding a consistent increase (by several orders of magnitude) of the molecular polarizability near metal surfaces. This mechanism is proposed as an alternative to assess the Surface Enhanced Raman Scattering (SERS) effect. I will discuss, in the framework of this model, some peculiarities of SERS: (i) the occurence of this effect especially when one uses noble metal surfaces (Au, Ag); (ii) the consistent increase of SERS when the metal surface is nanostructured; (iii) the observed dependencies of the SERS amplification factor on the distance between molecules and metal surfaces; (iv) the observed E4 dependence (E = electric field of the incoming electromagnetic radiation). In a second part of the seminar, I will analyze within the same framework the case of electrically polarizable media, with evidence of spontaneous polarization for some molecules, and for hysteretic behaviour of single molecules. I will also discuss some puzzling ferroelectric hysteresis curves observed experimentally. In a third part of the seminar, dynamic polarization effects, such as the effect of the Drude-Zener conductivity of the metal and the effect of retardation, will be taken into account,providing a connection between the dipole model and the plasmonic model,generally accepted to explain SERS.
Phase transitions in compressed baryonic matter with strangeness
Dr. Adriana Raduta, Dept. Fizica Nucleara, IFIN-HH
Present understanding of the high density phase of neutron stars and supernovae matter sustains the view that an important fraction of baryonic matter is made out of hyperons. In this context we investigate the possible phase transitions within a mean-field model. The thermodynamics of compressed strange baryonic matter is discussed with respect to the well known thermodynamics of diluted nuclear matter
from which it differs in many respects.
Hybrid functions and wavelets in control problems
Prof. Mohsen Razzaghi,
Head of Department of Mathematics and Statistics,
Mississippi State University MS 39762, USA,
Orthogonal functions have been applied to solve various problems of the dynamical systems. Much attention has been given to the solution of control problems. The approach is to convert the control problems to an algebraic equation. Signals frequently have mixed features of continuity and jumps. In such situations neither the continuous basis functions(such as Chebyshev, Laguerre, Legendre, etc) nor piecewise basis functions (such as block-pulse, Haar, Walsh, etc) taken alone would form an efficient basis in the representation of such signals. Recently, different types of hybrid functions (which are the combinations of block-pulse functions and continuous basis functions) and different types of wavelets (with continuous basis functions as mother wavelets) have been used for solving control problems and proved to be a mathematical power tool. In this talk we present the Legendre wavelets and hybrid functions of block-pulse with Legendre polynomials and block-pulse with Bernoulli polynomials. Numerical examples are included to demonstrate the applicability and the accuracy of the proposed method and a comparison is made with the existing results.
