Dr. Adrian Tanasa, DFT IFIN-HH
"Teoria de camp pe grup, candidat ca model de gravitatie cuantica"
Rezumat:
Teoria de camp pe grup a inceput sa se dezvolte in ultimii ani ca un nou candidat pentru un model de gravitatie cuantica. Aceasta teorie este o teorie tensoriala (de rang 3 pentru modele 3-dimensionale sau de rang 4 pentru modele 4-dimensionale) fiind in acelasi timp o generalizare naturala a modelelor matriciale 2-dimensionale. In acest seminar voi prezenta pe scurt ideile principale care stau in spatele acestei teorii precum si cateva dintre rezultatele existente deja in literatura.
Prof. Dr. D. Mihalache, DFT IFIN-HH
Proiect IDEI nr. 497/15.01.2009 "Fenomene si procese complexe in fizica informatiei cuantice", faza din Decembrie 2010:
Titlul fazei: "Stabilizarea vortexurilor optice localizate disipative spatiale (bidimensionale)".
Abstract: Am studiat atat prin metode analitice (variationale) cat si prin metode numerice, existenta si stabilitatea vartejurilor localizate bidimensionale de tip "crater vulcanic", precum si a cuadrupolilor care se formeaza intr-un mediu neliniar disipativ descris de ecuatia Ginzburg-Landau cu potential extern periodic bidimensional. In cazul in care potentialul extern este de tip oscilator armonic bidimensional, am aratat ca sunt stabile doar vartejurile cu sarcina topologica (vorticitate) S=1, precum si solitonii disipativi de tip dipol sau tripol.
Dr. Mihai Visinescu, DFT-IFIN,
Titlu: "Structuri spatio-temporale cu simetrii si abordari cuantice in gravitatie" (Programul IDEI, cod proiect 492, Contract
de finantare 571 / 2009)
Rezumat: " Au fost investigate simetriile de rang inalt intr-o formulare hamiltoniana. Abordarea covarianta a spatiului fazelor a fost extinsa pentru a include campuri de etalonare (gauge) externe si potentiale scalare. S-a dedus sistemul de ecuatii cuplate Killing generalizate si s-au dat constrangerile ce trebuie satisfacute pentru existenta integralelor prime de miscare. S-a pus in evidenta rolul tensorilor simetrici Stackel-Killing si antisimetrici Killing-Yano in generarea de marimi conservate, obtinandu-se conditiile necesare pentru ca simetriile originale ale sistemului fizic sa fie mentinute si in prezenta campurilor de etalonare (gauge). Simetriile si marimile conservate clasic au fost analizate la nivel cuantic. In general legile de conservare clasice nu se transfera la nivel cuantic, aparand asa numitele anomalii cuantice. Pe un spatiu-timp curbat datorita interactiilor gravitationale anomaliile cuantice reflecta tocmai violarea legilor de conservare clasice la nivel cuantic. S-a aratat ca simetriile de rang inalt nu conduc de regula la operatori cuantici conservati pentru ecuatiile Klein-Gordon sau Dirac. S-au identificat cateva circumstante favorabile notabile, in care existenta unor astfel de operatori de simetrie cuantici conservati sa fie posibila."
Dr. Irinel Caprini, DFT IFIN-HH
Titlu: Abordari moderne ale problemei divergentelor in teoria cuantica a campului (Program Idei, Cod CNCSIS 120; Contract IDEI-464/2009)
Rezumat: "Cercetarile din anul 2010 s-au axat pe doua directii: studii privind cresterea preciziei teoretice a predictiilor Modelului Standard al particulelor, si explorarea unor generalizari ale Modelului Standard, in special teoria corzilor. S-au obtinut constrangeri riguroase asupra factorilor de forma care parametrizeaza ratele dezintegrarilor semileptonice de interes pentru extragerea elementelor matricii de amestec Cabibbo-Kobayashi-Maskawa (CKM), s-a obtinut o determinare precisa a constantei de cuplaj $\alpha_s$ a cromodinamicii cuantice bazata pe o noua clasa de dezvoltari de perturbatie, si s-a demonstrat dualitatea dintre compactificarile corzilor heterotice si cele ale corzilor de tipul IIA."
Dr. Stefan Berceanu, DFT IFIN-HH
Titlu: "Limita comutativa a modelelor invariante la translatie pe spatiul Moyal" (Program IDEI, Contract 454/2008, cod CNCSIS 44)
Rezumat: "Renormarea teoriilor cuantice de camp pe spatiul necomutativ Moyal este ingreunata considerabil de aparitia unei probleme majore: amestecul ultraviole-infrarosu. Astfel, datorita anumitor faze oscilatorii ce (in spatiul impulsurilor) cupleaza impulsurile adiacente unui vertex, in amplitudinile Feynman ale grafurilor neplanare apar anumite faze ce cupleaza impulsurile externe si cele externe. Aceste faze imbunatesc comportamentul ultraviolet al amplitudinilor Feynman respective. Atunci cand aceste grafuri neplanare sunt la randul lor introduse in alte grafuri mai «mari», impulsurile externe (de care depinde amplitudinea Feynman respectiva) devin interne si ele trebuiesc bineinteles integrate. Totul se traduce prin aparitia unor noi divergente in regimul infrarosu al acestor impulsuri. Numele de amestec ultraviolet/infrarosu provine din faptul subgraful pentru care impulsurile respective sunt impulsuri externe se afla in regimul ultraviolet al impulsurilor sale interne, dar divergenta apare cand impulsurile respective (impulusuri externe pentru subgraf) sunt in regimul infrarosu"
Dr. George Nemes
Titlu: "Metamateriale - materiale cu indice de refractie negativ"Rezumat: "Denumirea de “metamaterial” a fost introdusa in 2001 dupa ce in anul 2000 s-a obtinut prima structura cu aceste proprietati noi (indice de refractie negativ), in domeniul microundelor, dupa o idee teoretica lansata in 1967 de Prof. rus Victor Veselago. In acest seminar se prezinta conceptele de baza ale noului domeniu, o scurta istorie a lui, bazele fizice ale existentei unui indice de refractie negativ pentru anumite materiale, consecintele fizice specifice, si evolutia spectaculoasa a domeniului in decada 2000-2010. De asemenea, se prezinta pe scurt aplicatiile potentiale care se prevad si care justifica interesul major in acest domeniu, manifestat prin injectarea unor sume de miliarde de dolari in cercetarea si dezvoltarea domeniului."
Dr. Madalina Boca, Asist. Univ. Bucuresti,
Titlu: "Radiation scattering in the high intensity regime"
Rezumat: "The subject of this work (authors: M. Boca, V. Florescu, V. Dinu) is the scattering of a very intense plane wave laser pulse (intensity I>10^4 au) on relativistic electrons with Lorentz factor between 10 and 45. We start by discussing the relation between the classical and quantum treatment of the process. For a pulse with the central wavelength 1060 nm and circular polarization, we study systematically the angular distribution of the emitted radiation, in its dependence on the electron energy, for two collision geometries: the head-on collision (counterpropagating electron and laser pulse), and the 90 degrees collision (the initial electron momentum orthogonal to the laser propagation direction). We investigate the relation between the emitted radiation and the trajectory followed by the electron velocity during the laser pulse and, for the case of a short laser pulse, we discuss the carrier-envelope phase effects. We also present, for the two mentioned geometries, an analysis of the polarization of the emitted radiation and a comparison of the results predicted by the exact classical formula with a high-energy approximation of it."
Ionel Stetcu, University of Washington
Titlu: "Nuclear structure and dynamics in a time-dependent SLDA framework"
Rezumat:
The Time-Dependent Superfluid Local Density Approximation (TD-SLDA) is a local extension of the Time-Dependent Density Functional Theory
(TD-DFT) to superfluid fermion systems, and as such it can be viewed in general as a reformulation of the exact quantum mechanical time evolution of a many-body system, when only single-particle properties are considered. TD-DFT has been applied for quite some time to a large number of normal condensed matter and nuclear systems, and to complex molecules, typically in order to evaluate their linear response (RPA) to a variety of external probes. The full implementation of the 3D TD-SLDA, without any symmetry constrains, requires the use of the largest parallel computers, and it was only recently achieved. I present results regarding the collective excitation spectra for fermionic systems, and in particular I will show examples of the dynamics of the pairing correlations, which could not be encapsulated within more traditional approaches, such as the quantum hydrodynamics of superfluid systems or the Landau-Ginzburg approach. Finally, I will show the first applications of the large scale TD-SLDA calculations to low-energy neutron-induced reactions.
Prof. Dr. Ionel Stetcu (University of Washington, SUA)
Titlu: Ab initio methods in no-core shell model and cold atoms
Rezumat: In this talk, I will present current developments in ab initio calculations. After a short presentation of the ab initio methods, including current approaches to determining the inter-nucleon interactions, I will concentrate on the no-core shell model (NCSM). In the last part, I will present the latest applications of NCSM to the harmonically trapped few-body systems of cold atoms characterized by interactions with large scattering lengths, and will discuss their relevance for applications to nuclear physics.
Dr. Aurelian Isar, DFT IFIN-HH
Titlu: Studiul dinamicii entanglementului (corelatiilor cuantice) in sisteme cuantice deschise (Faza 2/2010 a Proiectului Nucleu PN 09 37 01 02).
Rezumat: "In cadrul teoriei sistemelor cuantice deschise bazate pe semigrupuri dinamice cuantice complet pozitive este studiata influenta difuziei si disiparii asupra evolutiei temporale a entanglementului (corelatiilor cuantice) in sisteme de variabile continue. Este descrisa relatia dintre decoerenta cuantica si entanglementul cuantic si este estimat gradul de intensitate a entanglementului in sisteme cuantice deschise bipartite."
Dr. Calin Lazaroiu, Trinity Colleage, Dublin, Irlanda
Titlu: "Corzi, topologie si n-categorii -- conexiuni si implicatii"
Rezumat: Conexiunea dintre teoria corzilor si anumite probleme in topologia simplectica si in geometria algebrica enumerativa este bine-cunoscuta. In acest talk, voi prezenta o schita a rezultatelor obtinute in acest domeniu si voi discuta anumite extensii ale acestei conexiuni care au implicatii pentru programul n-categoriilor initiat de catre A. Grothendieck, un program care atrage interes re-innoit in lumina rezultatelor obtinute recent de catre Lurie. Ca exemplu, voi schita anumite generalizari ale teoriei Chern-Simons care conduc la notiunea de torsiune analitica extinsa cat si conexiunea dintre acest punct de vedere si anumite rezultate obtinute recent de catre Igusa. "
Dr. M. Mirea, DFT IFIN-HH,
raport de faza: "Efect par-impar in fisiunea la energii joase" (proiectul IDEI, contract nr. 512)
Rezumat: Se analizeaza distributiile experimentale ale randamentelor de fragmentelor de fisiune pentru partitii pare si impare cu ajutorul unui model dinamic de spargere de perechi Coopper bazat pe efectul Landau-Zener generalizat pentru sisteme superfluide. Se explica efectul par-impar in fisiunea rece.
Dr. M. Mirea, DFT IFIN-HH,
Titlu: "Bariere de fisiune dinamice pentru actinide" (faza contract MODUL 3 CERN)
Rezumat: Bariere de fisiune pentru actinide sunt calculate cu ajutorul modelului macrosocopic-microscopic bazat pe modelul in paturi cu doua centre Woods-Saxon. Se calculeaza traiectorii de fisiune in spatiul configuratiilor cu cinci grade de libertate. Se obtine un acord bun cu valorile experimentale.
Prezinta: Prof. Dr. K. Pomorski, Theoretical Physics Department Maria Curie Sk lodowska University, PL-20-031 Lublin, Polonia
Titlu: Masses and fission barriers of nuclei in the LSD model
Rezumat:
The recently developed Lublin-Strasbourg Drop (LSD) [K. Pomorski, J. Dudek, Phys. Rev. C67, 044316 (2003)] model together with the microscopic corrections taken from Ref. [P. Moeller et al., At. Data Nucl. Data Tab. 59, 185 (1995)] is very successful in describing many features of nuclei. In addition to the classical liquid drop model the LSD contains the curvature term proportional to the A1/3. The r.m.s. deviation of the experimental binding energies of 2766 isotopes with Z,N ≥ 8 versus those predicted by the LSD model, equal to 0.698 MeV, is smaller than the ones given by other more elaborated theories. It turns out that the LSD model gives also a rather satisfactory prediction of the fission barrier heights. It is worth emphasising that all the parameters of the LSD model were fitted to the nuclear masses only and thus the correct reproduction of the barrier heights can be seen as an additional sign of the intrinsic consistency of the model. The mean square deviation of the barrier heights from experiment is 3.56 MeV, but it decreases to only 0.88 MeV when only the nuclei with Z ≥ 70 are considered. In addition, it was found in Ref. [K. Pomorski, J. Dudek, Int. Journ. Mod. Phys. E13, 107 (2004)] that taking into account the deformation dependence of the congruence energy proposed by ´ Swi¸atecki significantly approaches the theoretical LSD- model barrier-heights to the experimental data in the case of the light isotopes while the fission barriers for heavy nuclei remain nearly unchanged and agree well with experiment. It was also shown in Ref. [A. Dobrowolski, K. Pomorski, and J. Bartel, Int. Journ. Mod. Phys. E16, No. 2, (2007)] that the saddle point masses of transactinides from 232Th to 250Cf evaluated using the LSD differ by less than 0.67 MeV from the experimental data. In addition, the topographical theorem of ´ Swi¸atecki was successfully applied to estimate the fission barrier heights within the pure LSD model i.e. without the shell correction in the saddle point. According to this theorem the barrier height should be equal to the difference of the macroscopic mass at the saddle and the measured mass in the ground state [F. Ivanyuk and K. Pomorski IJMPE 19 (2010) 514]. Different shape parametrisations were also compared with the optimal in energy LD shapes of fissioning nuclei obtained by solving an appropriate Langevin-Eular differential equation [F. Ivanyuk and K. Pomorski, Phys. Rev. C79 (2009) 054327.]
Titlu: Studiul calitatii solutiei numerice a ecuatiei Schrodinger de canale cuplate (proiect IDEI-119)
Rezumat: Testarea calitatii rezultatelor produse de o metoda numerica se face de obicei prin alegerea unui set de ecuatii a caror solutii,
cunoscute sub forma analitica, sunt folosite pentru comparare. Testarea nu ridica probleme speciale pentru cazul ecuatiei Schrodinger cu un singur canal deoarece exista mai multe ecuatii cu solutie analitica cunoscuta (potential coulombian, de oscilator armonic, Morse, Hulthen, Poeschl-Teller etc.). Mai mult, faptul ca fiecare dintre aceste potentiale contine parametri liberi (sarcina electrica in potentialul coulombian sau
frecventa in oscilatorul armonic) fac ca rezervorul de probleme de test sa fie destul de generos. Situatia este diferita pentru ecuatia de canale cuplate. Aici numarul de probleme cu solutie analitica cunoscuta este nesemnificativ si prin urmare problema constructiei unor astfel de probleme devine stringenta. O problema de acest tip a fost construita in cadrul fazei si ea va fi prezentata in cadrul seminarului. Problema are solutii analitice pentru toate cazurile in care elementele matricii potentialului sunt de forme pentru care ecuatia de un singur canal este rezolvabila exact si prin urmare ea se bucura de proprietatea de a avea mai multi parametri liberi. Ca aplicatie vom arata cum aceasta problema poate fi folosita pentru testarea codurilor bazate pe metoda Numerov.
Title: Drag Force and Hess-Fairbank Effect in the One-Dimensional Bose Gas
Abstract: Different aspects of superfluidity in one dimension (1D) are discussed. It is shown that the Hess-Fairbank effect takes place in 1D at zero temperature. In particular, the rotational inertia of an interacting 1D Bose gas in a finite ring is zero. Nevertheless, our results indicate that the frictionless motion of impurities depends sensitively on the strength of interactions in the gas. In general, this is possible only in a limit of weak interactions. We obtain the phase diagram of frictionless motion for the gas immersed into a moving shallow optical lattice. In this case the drag force, a quantitative measure of superfluidity, can be zero at specific values of lattice velocity and the gas density even for strong interactions.
Prof. Dr. Anca Tureanu, Universitatea din Helsinki si Institutul de Fizica din Helsinki
Titlu: Relativitatea Foarte Speciala si Spatiul-Timp Necomutativ
Rezumat: Relativitatea Foarte Speciala (Very Special Relativity - VSR) introdusa de Cohen si Glashow are o realizare matematica robusta pe spatii necomutative, in special in planul Moyal cu necomutativitate de tip light-like. Realizarea este legata in mod esential de algebra twisted Poincare si rolul ei ca simetrie a spatiu-timpului necomutativ si a teoriilor cuantice de cimp pe astfel de spatii. In realizarea noastra, teoriile cu invarianta VSR contin un singur parametru de deformare, si anume scala necomutativitatii $\Lambda_{NC}$. Analizele preliminare cu datele existente indica $\Lambda_{NC}\geq 1-10\ {\rm TeV}$.
Fine tuning and new physics beyond the MSSM Higgs sector
Dr. Dumitru Ghilencea, DFT, IFIN-HH
The MSSM spectrum that corresponds to minimal fine tuning is computed and provides a benchmark for future searches. It is characterised by heavy squarks and sleptons and light neutralinos, charginos and gluinos. Without imposing the LEP Higgs mass bound it is shown that the smallest fine tuning (1:13) consistent with a relic density within the WMAP bound corresponds to a preferred Higgs mass mh of 114 ± 2 GeV. Fine tuning rises exponentially for a Higgs mass above this value. Failing to detect a Higgs near this value, a larger fine tuning corresponding to a heavier Higgs may indicate the existence of additional, "new physics" in the MSSM Higgs sector. To explore this possibility, we consider all effective operators of dimensions d=5 and d=6 that can parametrize this "new physics", evaluate their corrections to mh and identify the operators with the largest individual corrections. It is shown that one can have an increase of mh above the LEP bound due to d=6 operators, even for a scale of new physics above the LHC reach, while still reducing the MSSM fine-tuning for mh>120 GeV.
Dl Paul Stoica, doctorand
Titlu: "Efecte de structură în dezintegrări nucleare"
Rezumat: Gasirea de noi elemente de sinteza si incercarea explicarii proprietatilor fizice ale acestora, a impins adaptarea vechilor modele nucleare la noile conditii. Pentru explicarea unor fenomene ce apar in dezintegrari nucleare cum ar fi: rezonanţe în a doua groapă de potenţial pentru secţiunea eficace de fisiune indusă de neutroni sau fuziunea la rece pentru sinteza elementelor supragrele, s-a dezvoltat un model microscopic-macroscopic avand la baza oscilatorul cu doua centre. Rezultatele teoretice obtinute cu acest model sunt comparate, acolo unde este cazul, cu valori experimentale.
and
Dr. Mihai Visinescu, Depart. Theor. Phys. Inst. Physics Nucl. Eng., IFIN-HH Magurele, Bucharest, Romania
Title: Spinor Description of Perfect Fluid and Dark Energy; spinor description of a Bianchi type-I model with cosmic string
Abstract: Recently, in a number of papers it was shown that depending on the choice of parameters such as coupling constant, order of nonlinearity etc. a spinor field can (i) eliminate space-time singularity; (ii) accelerate isotropization process of the initially anisotropic space-time and (iii) explain the accelerated expansion of the Universe. So it was natural to ask if the nonlinear spinor field can model a perfect fluid or dark energy. In this report we give the spinor description of perfect fluid and dark energy and show advantage of spinor description in solving many cosmological problems. The nonlinear spinor field approach is used to investigate a Bianchi type-I model with cosmic string in the presence of a magnetic field.
References:
B. Saha, Cent. Eur. J. Phys., in press (2010); arXiv:0901.1387
B. Saha, M. Visinescu, Int.J.Theor.Phys,, in press (2010); arXiv:0906.0156
Rezumat:
Este folosit un principiu variational dependent de timp pentru decuantizarea unui Hamiltonian bozonic cvadrupolar de ordinul doi. Ecuatiile clasice pentru coordonatele generalizate precum si constrangerea pentru momentul cinetic sunt cuantificate si rezolvate analitic. Pentru energii este obtinuta o formula Holmberg-Lipas generalizata. O dependenta J(J+1) similara este oferita de modelul starilor coerente (CSM) in regimul deformarilor mari, prin folosirea unei dezvoltari a energiei in serie de puteri ale lui 1/x, x fiind patratul parametrului de deformare. O expresie compacta simpla este de asemenea posibila si pentru regimul aproape vibrational. Aceste trei expresii au fost folosite pentru 44 nuclee acoperind regiuni ale tabelului nuclizilor caracterizate de diferite simetrii dinamice sau in alte cuvinte apartinand diferitor faze nucleare. Au fost de asemenea considerate nucleele ce satisfac simetriile specifice punctelor critice in tranzitiile de faza O(6) -> SU(3), SU(5) -> SU(3). Acordul dintre rezultatele numerice si datele experimentale corespunzatoare este foarte bun. Acest lucru este reflectat in valorile foarte mici ale abaterilor standard.
Drd. Asistent de cercetare Petrica Buganu
Titlu: "O descriere fenomenologica a multipletilor 4+ si 6+"
Rezumat:
"Formalismul folosit in descrierea multipletilor 0+ si 2+ dintr-o lucrare anterioara (A. A. Raduta et al., Jour. Phys. G: Nucl. Part. Phys. 36
(2009) 055101) este extins pentru a descrie urmatorii multipleti 4+ si 6+. Hamiltonianul model consta intr-un Hamiltonian bozonic cvadrupolar de ordin sase care este tratat atat semiclasic cat si exact. Energiile calculate prin aceste doua metode sunt comparate cu datele experimentale corespunzatoare multipletilor 4+, respectiv, 6+. S-au pastrat aceleasi nuclee ca cele din lucrarea anterioara, si s-au pastrat de asemenea parametrii fitati deja pentru multipletii 0+ si 2+ corespunzatori fiecarui nucleu considerat."
Classical optics-quantum physics analogies
Prof. Dr. Daniela Dragoman Univ. Bucharest, Physics Dept.
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Abstract:
We show that the behavior of several quantum physical systems, in particular ballistic electrons in common semiconductors and quantum optical fields, can be mimicked by classical optical systems in certain conditions. In the case of ballistic electrons the analogy with classical optics is based on the formal similarities between the evolution laws of electromagnetic fields and the Dirac or time-independent Schrödinger equations. While these analogies could have a practical importance, since they could be used to test the behavior of quantum systems with classical means, they are also important in revealing the differences between the classical and the quantum realms. On the other hand, the analogies between classical and quantum optics gravitate around the concepts of coherence and entanglement. Theories and experiments show the subtle differences between these concepts in quantum and classical theories.
Dr. Victor Barsan, DFT IFIN
Titlu: Metode operatoriale in studiul oscilatorului anarmonic cuartic cu aplicatii in fizica statistica a sistemelor cvasi-uni-dimensionale.
Rezumat:
Prin aplicarea rotatiilor Jacobi infinitezimale, Hamiltonianul anarmonic este succesiv transformat pana cand, asimptotic, devine diagonal. Neglijand ternenii nesemnificativi pentru calcularea primelor nivele energetice, se obtin ecuatii neliniare de curgere (flow equations), care se pot integra numeric, gasindu-se un Hamiltonian diagonal, ale carui stari proprii sunt starile oscilatorului armonic. Primele nivele energetice se obtin usor si pot fi folosite in evaluarea fizicii statistice a unui sistem cvasi-uni-dimensional, asociat oscilatorului cuartic prin metoda matricei de transfer.
Seminar DFT, 06/05/2010
Prezintă: Dr. Doru Delion, DFT, IFIN-HH
Titlu: Efecte anarmonice în tranziţiile nucleare de tip beta şi dublu beta
Dr. Dan Grigore, DFT IFIN-HH
Tema: "Anomalii cuantice si cimpuri off-shell"
Rezumat:
Consideram teoria cuantica a cimpurilor folosind formalismul teoriei axiomatice a cimpurilor in varianta on-shell (pe suprafata de masa) si off-shell (in afara suprafetei de masa). Teoria perturbativa a cimpurilor este definita in cadrul formalismului cauzal al lui Epstein-Glaser. Formalismul este ilustrat pina in ordinul al doilea al teoriei perturbatiilor. Apoi folosim formalismul on-shell si off-shell pentru un model cu invarianta la etalonare: QCD (cromodinamica cuantica). In sfirsit, aratam cum se pot calcula anomaliile cuantice din ordinul al doilea al teoriei perturbatiilor folosind formalismul off-shell.
Titlu: "Single particle models for bound systems: I. Two-body systems in classical and quantum non-relativistic mechanics"
Rezumat:
We show that a classical two-body bound system in its rest frame is equivalent to a system made of two single-particle sub-systems, individually bound to a center of forces which coincides with the center of mass. Accordingly, the single-particle sub-systems are individually quantized and the wave function of the bound system, expressed as product of individual wave functions with correlated arguments, is really a single-particle wave function: it is invariant at translations, retains the intrinsic properties of the internal particles and is in perfect agreement with the image of a bound system in classical mechanics.
"How to approach cutting edge studies of strongly interacting matter ? ALICE - from R&D to First Physics"
Mihai Petrovici on behalf of NIHAM
Abstract: A short review of the main contributions of DFH during the R&D, construction, installation, computing infrastructure and first experiment using ALICE experimental device, will be presented in the beginning. The first ALICE physics results will be followed by detailed presentation of the analysis activities in our department and preliminary physics results from p + p collisions at 900 GeV in terms of as a function of hadron mass - do we have signature for collective expansion, at which stage of strongly interacting matter ? Medium and long term research perspectives using ALICE @ LHC will be underlined in last part of the presentation.
M. Rizea and N. Carjan
"Accurate numerical solution of time-dependent Schroedinger equation with time-dependent potentials"
Abstract:
We discuss some procedures to improve the accuracy of the numerical solution of the time-dependent Schr\"{o}dinger equation with a time-dependent potential. In particular, a modification of the standard finite difference method by an exponential fitting Numerov formula leading to a higher order ($6$ instead $4$) in the approximation of the second spatial derivative in the Hamiltonian along with a better description of oscillating or exponential behavior, a propagation scheme of order $5$ with respect to the time step, based on the Magnus expansion and artificial boundary conditions aimed to reduce the reflections of the wave packet at the numerical boundaries are presented. The procedures are illustrated on a test equation with analytic solution.
Author: Eugeniu E. Radescu
"Variational, systematically improvable schemes for calculation of nonperturbative quantities in Quantum Field Theories"
Abstract
New proposals for variational, nonperturbative methods are being investigated in the case of critical scalar O(2) three dimensional fi^4 field theory, which greatly improve the rate of convergence by incorporating the possibility of non-trivial critical exponents in the approach to critical limit. When the possibility of a new variable related to critical exponents is incorporated, the convergence is exponential to the correct, nonperturbative result. Moreover, these proposals are part of a systematically improvable scheme which can be useful in practical calculations of nonperturbative quantities in field-theoretical problems.
Dr. Gheorghe Stratan, DFT-IFIN.
Titlu: "Sidereus Nuncius", de Galileo Galilei. 400 de ani de la publicare: Imprejurari si semnificatii".
Rezumat:
Aparitia "Mesajului de la stele", la 13 martie 1610 (in 550 de exemplare, vandute in acceasi luna) marcheaza piatra de hotar dintre astronomia
practicata cu ochiul liber si astronomia optica, activa si astazi. Sunt prezentate descoperirile lui Galilei, semnificatia lor si reactiile contemporane.
Dr. Calin Alexa, DFPE-IFIN
Titlu: Large Hadron Collider @ CERN
Rezumat: Large Hadron Collider (LHC) de la CERN, este un instrument stiintific gigantic care are 26 km lungime fiind construit la o adincime
de aproximativ 100 m intinzindu-se pe teritoriul Frantei si Elvetiei. Proiectarea sa a inceput in 1980 iar aprobarea inceperii constructiei dateaza din 1994. LHC si-a reinceput functionarea in Noiembrie 2009 cind avut loc ciocniri proton-proton la 900 GeV; citeva zile mai tirziu s-a ajuns la energia de 1.18 TeV. Primele ciocniri la 7 TeV (3.5 TeV pe fascicul) vor avea loc in primul trimestru al anului 2010.
Dl. Dorel Pietreanu (doctorand, conducator doctorat Dr. Mihai Visinescu)
Referate de doctorat:
- Studiul atomilor kaonici
- Experimentul SIDDHARTA: rezultate si performante (Abstract)
Atomii kaonici fac parte din categoria atomilor exotici. Acestia se formeaza atunci cand o particula incarcata negativ (pion, miuon, kaon ) Г inlocuieste unul din electronii de pe orbitele superioare ale atomului. Atomii exotici sunt folositi ca instrument de studiu in mai multe domenii ale fizicii, dintre care cele mai importante sunt studiul interactiilor fundamentale (interactia tare in cazul atomilor hadronici ) si a simetriilor fundamentale (testarea CPT folosind heliul antiprotonic si antihidrogenul). In particular studiul unui atom hadronic simplu (ex. hidrogenul kaonic), permite o investigare directa a interactiei tari antikaon-nucleon la energii joase. Desi in cazul acestui sistem interactia fundamentala este cea electromagnetica, experimental se poate observa o deplasare si o largire a nivelului energetic 1s datorate interactiei tari precum si a timpului redus de viata al acestui atom exotic. In experimentul SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) s-au studiat urmatoarele sistemele de atomi exotici: hidrogenul, heliu si deuteriu kaonic (prima masuratoare din lume). Vor fi prezentate rezultatele obtinute si implicatiile acestora. Bibliografie: - S. Okada, D. Pietreanu et al., "Precision measurement of the 3d---> 2p x-ray energy in kaonic He-4", Phys. Lett. B653 (2007) 387 - V. Lucherini, D. Pietreanu et al., "Hadronic atoms physics at DAFNE", Int. J. Mod. Phys. A22 (2007) 479 - T. Ishiwatari, D. Pietreanu et al., "Silicon Drift Detectors for the kaonic atoms X-ray measurements in the SIDDHARTA experiment", Nucl. Instrum. Meth., A581 (2007) 326 - M. Bazzi, D. Pietreanu et al., "Kaonic helium-4 X-ray measurement in SIDDHARTA", Phys. Lett. B681 (2009) 310 - J. Zmeskal, D. Pietreanu et al., "Kaonic atoms at DAFNE: The SIDDHARTA experiment", Int. J. Mod. Phys. A24 (2009) 190
Dr. Mirela Babalic, DFT-IFIN
"Interactii intre colectii de campuri tensoriale nemasive cu simetriile mixte (3,1) si (2,2)"
Lucrand in ipotezele generale standard asupra deformarilor (localitate spatio-temporala, analiticitate in constanta de cuplaj, covarianta Lorentz, invarianta PoincarГ© si conservarea ordinului derivativ maxim al ecuatiilor de camp pentru teoria cu interactie in raport cu cea libera) investigam self-interactiile si cross-interactiile consistente intre doua colectii de campuri tensoriale nemasive cu simetriile mixte (3,1) si respectiv (2,2) folosindu-ne de teoria deformarilor bazata pe formalismul BRST anticamp si de tehnici specifice de coomologie BRST locala. Am obtinut ca: a) nu apar self-interactii care sa deformeze transformarile gauge originale, b) apar cross-interactii consistente intre cele doua colectii de campuri in ordinele unu si doi in constanta de cuplaj astfel incat o parte din generatorii gauge si din functiile de reductibilitate sufera deformari, c) existenta sau inexistenta cross-interactiilor intre diferite campuri cu simetria mixta (2,2) depind de comportamentul indefinit, sau respectiv pozitiv-definit al matricii tensorului metric corespunzator.
Dr. Petre Dita, DFT-IFIN
"New Hadamard Matrices from Mutually Unbiased Bases"
An analytical method for getting new complex Hadamard matrices by using mutually unbiased bases and doubling formulas is provided. The method is illustrated with the n=4 case that lead to a rich family of eight-dimensional Hadamard matrices depending on five arbitrary phases.
"Stable configurations of deposited atomic clusters"
Deposited atomic cluster configurations are investigated under the hypothesis of spheroidal cap shapes being a stable geometry as a result of cluster-surface interaction. The macroscopic-microscopic method is employed to calculate the deformation energy. A specialized single-particle shell model (jellium type) is developed in order to account for the quantum effects, and the liquid-drop approach is used to calculate the macroscopic part of the energy. The minima within the total deformation energy are interpreted as equilibrium states of atomic clusters on surfaces. Calculations have been performed for the atom numbers N=20, 70 and 200.
Dr. Aurelian Isar, DFT-IFIN
"Entanglement dynamics of two-mode Gaussian states in a thermal environment"
Within the framework of the theory of open systems based on completely positive quantum dynamical semigroups, we give a description of the continuous variable entanglement for a system consisting of two uncoupled modes interacting with a thermal environment. Using the Peres-Simon necessary and sufficient criterion for separability of two-mode Gaussian states, we describe the generation and evolution of entanglement in terms of the covariance matrix for a Gaussian input state. For some values of the temperature of environment, the state keeps for all times its initial type separable or entangled. In other cases, entanglement generation, entanglement sudden death, or a periodic collapse and revival of entanglement take place. We analyze also the time evolution of the logarithmic negativity, which characterizes the degree of entanglement of the quantum state.
Dr. Lucia Popa, ISS
"Higgs mass from cosmological and astrophysical measurements"
