Pairing and quartetting in nuclei: from exactly solvable models to realistic calculations.
Nicolae Sandulescu
08.12.2016
Abstract:
In atomic nuclei pairing forces generate 4-body "quartet" correlations which cannot be accounted for by standard BCS models. For like-particle pairing forces these correlations are in fact contained in the exactly solvable SU(2) model of Richardson. Exactly solvable SO(5) and SU(4) models predict aslo quartet correlations for isovector and isovector-isoscalar pairing forces. I will discuss how alpha-like quartet correlations emerge as well in realistic calculations, both in even-even [1,3] and odd-odd nuclei [2,4].
1. M. Sambataro and N. Sandulescu, Phys, Rev. C93, 054320 (2016)
2. M. Sambataro and N. Sandulescu, Phys. Lett. B763, 151 (2016)
3. M. Sambataro and N. Sandulescu, Eur. Phys. J. A, submitted
4. D. Negrea, N. Sandulescu and D. Gambacurta, in preparation
Seminarul contine un rezumat al rapoartelor stiintifice pentru: Proiect Nucleu nr. 16 42010/2016 (raport de etapa) Proiect Idei nr. 57/5.10.2011 (raport final)
Uniform asymptotic approximation for 3D quantum scattering by a non-central potential
N. Grama, DFT
24.11.2016
Abstract
An Ansatz based on an etalon function generated by the problem itself is used in order to obtain a uniform asymptotic approximation of the 3D wave function for the scattering by a non-central potential. The obtained uniform asymptotic approximation removes the singularities at the caustics that occur in the 3D WKB approximation. The scattering amplitude provided by the uniform asymptotic approximation contains the poles that are the fingerprints of the system. The comparison of the obtained uniform asymptotic approximation of the 3D scattering wave function with the exact scattering wave function shows the versatility of the Ansatz based on an etalon function generated by the problem itself.
Investigarea structurii nucleelor grele si supragrele cu ajutorul emisiei alfa
Dumitrescu Alexandru
15.11.2016
Abstract:
Voi prezenta rezultatele principale ale tezei mele de doctorat după următoarea structură. În prima parte voi vorbi despre o lege universală de dezintegrare satisfăcută de toate tranzițiile α observate până în prezent și despre o generalizare simplă a regulii Viola-Seaborg la tranziții α pe stări excitate. În partea a doua voi prezenta o variantă a modelului stărilor coerente (CSM) utilă pentru descrierea spectrului de emisie α în nuclee par-pare și cu numărul de masă impar. În partea a treia voi prezenta o metodă de calcul a structurii fine a spectrului de emisie α pentru tranziții pe stări de deformare cuadrupolară în nuclee par-pare, respectiv tranziții favorizate pe stări rotaționale în nuclee cu numărul de masă impar. Tehnica folosită constă în rezolvarea unei ecuații de canale cuplate pentru un potențial α-nucleu fiică alcătuit din doi termeni. Primul termen este construit din potrivirea unui oscilator armonic cu o interacție cu simetrică sferică obținută din integrarea forței nucleon-nucleon M3Y, iar al doilea termen este dat de o interacție cuadrupol-cuadrupol (QQ) ce include deformarea nucleară calculată în modelul CSM. Stările care dezintegrează prin emisie α sunt identificate cu cele mai joase rezonațe înguste obținute prin rezolvarea ecuației de canale cuplate pentru potențialul descris anterior. Rapoartele de ramificație α către primele stări excitate sunt reproduse cu ajutorul tăriei interacției QQ. Rezultatele acestei metode sunt în bună concordanță cu datele experimentale pentru tranzițiile pe stări excitate de energie mai înaltă. Sunt prezise rapoarte de ramificație pentru tranziții ce încă nu au fost observate, inclusiv pentru cazul nucleelor supragrele par-pare. Este indicată o legătură interesantă dintre lărgimile reduse de dezintegrare și tăria tranzițiilor electrice de tip cuadrupolar.
Low-Energy Hadronic Contributions to Muon g-2
Irinel Caprini, DFT
20.10.2016
Abstract
Along with the direct searches of new particles at the LHC, low-energy phenomenology offers many complementary ways to search for physics beyond the Standard Model. However, these searches are often hindered by the insufficiently precise knowledge of the hadronic contributions. I will discuss for illustration several topics (direct Dark Matter searches, anomalies in flavor physics, proton charge radius puzzle and the muon g-2 problem), considered at the recent Workshop on "Hadronic Contributions to New Physics Searches", 25-30 September 2016, Tenerife, Spain. Then I will present in more detail a recent approach to improve the accuracy of the theoretical determination of the low-energy hadronic contribution to muon g-2 (work realized in the frame of the Project Idei, PN-II-ID-PCE-2011-3-0264, Contract Nr. 121/2011).
Influence of pairing interaction on the fusion cross section
Radu A. Gherghescu, DFT
29.09.2016
Abstract
The pairing interaction is studied within the binary deformed two center models. Its influence exerts upon the cross section through two terms: the deformation energy of the binary system configuration and the mass tensor. These two quantities have been used in the calculation of the cross section for a wide range of mass asymetries, in the synthesis of superheavy nuclei. We calculated the pairing correction within the Bardeen-Cooper-Schrieffer formalism. The binary character of the process is induced by the single particle energy levels obtained with the deformed two-center shell model. Again the binary feature influences the fusion process through the occupation probabilities of a level by the nucleon pair, as being components of the mass tensor, here obtained with the cranking theory. We show that the pairing influence upon the cross section for synthesis is mass asymetry dependent and is responsible for about 10 procents of the cross section value in the sub-barrier fusion cross section.
Nuclear fission of superheavy nuclei
Dorin N. Poenaru, DFT
29.09.2016
Abstract
In 1928 G. Gamow as well as Condon & Gurney gave the first explanation of alpha decay as a quantum tunnelling of a preformed particle at the nuclear surface. Soon after experimental discovery in 1984 by Rose & Jones of cluster radioactivity, confirming earlier (1980) predictions by Sandulescu, Poenaru & W. Greiner (see Encyclopaedia Britannica Online), a microscopic theory also explained the phenomenon in a similar way. Here we show for the first time that in a spontaneous cold fission process the shell plus pairing corrections calculated with Strutinsky's procedure may give a strong argument for preformation of a light fission fragment near the nuclear surface. It is obtained when the radius of the light fragment, R2, is increased linearly with the separation distance, R, of the two fragments, while for R2=constant we obtain the well known two hump potential barrier. We use the asymmetric two center shell model, the Yukawa-plus-exponential liquid drop amd the cranking inertia tensor with BCS pairing.
Protecting quantum circuits with surface code quantum error correction
Alexandru Paler, Johannes Kepler University Linz, Austria
21.09.2016
Abstract
Arbitrarily reliable execution of quantum circuits can only be achieved through error correction. This talk will introduce existing techniques for transforming an uncorrected circuit into one using surface code quantum error correction. Examples of error corrected circuits obtained using current generation software will be presented during the talk.
Transverse momentum distribution of hadrons in the Tsallis statistics
Alexandru Parvan (DFT, IFIN-HH, Bucharest & BLTP, JINR, Dubna)
15.09.2016
Abstract
The analytical expression for the ultrarelativistic transverse momentum distribution of the Tsallis statistics was obtained. We found that the transverse momentum distribution of the Tsallis-factorized statistics, which is now largely used for the description of the experimental transverse momentum spectra of hadrons measured in pp collisions at LHC and RHIC energies, in the ultrarelativistic case does not recover the transverse momentum distribution of the Tsallis statistics and it is equivalent only to the transverse momentum distribution of the Tsallis statistics in the zeroth term approximation with transformation of the parameter q to 1/q_{c}. Moreover, we rigorously demonstrated on the base of the ultrarelativistic ideal gas that the Tsallis-factorized statistics is not consistent with both the Tsallis statistics and the Tsallis-2 statistics. The energy dependence of the parameters of the Tsallis statistics for the pions produced in pp collisions at high energies was studied.
Studiul cuantificarii Berezin pe domenii Siegel-Jacobi
Stefan Berceanu
15.09.2016
Abstract
S-a determinat matricea metricii bulei Siegel-Jacobi si inversa ei si s-au calculat curbura scalara, forma Ricci si operatorul Laplace-Beltrami pe aceasta varietate. Se evidentiaza aspecte geometrice ale cuantificarii Berezin pe varietati Kaehler omogene in cazul bulei Siegel-Jacobi.
Referinte:
Berceanu S., Balanced metric and Berezin quantization on the Siegel-Jacobi ball, SIGMA 12, 064, 28 pages (2016);
Berceanu S., Geodesics associated to the balanced metric on the Siegel-Jacobi ball, arXiv: 1605.02962v1
Mentiune: Seminarul este cuprins ca activitate in contractul PN 16 42 01 01
Quasi-exact solutions for the Bohr Hamiltonian with sextic oscillator potential
Petrica Buganu, DFT
08.09.2016
Abstract
Quantum models whose energy levels and corresponding wave functions can be determined algebraically and have analytical expressions are known as exactly solvable. These models play a very important role in physics, because the exact solvability is always related to a symmetry obeyed by the system. Unfortunately, the variety of exactly solvable models is quite small and exhausted. There is however a way to expand their properties by relaxing the condition of having the whole spectrum in a closed form. Basically, such extensions lead to spectral problems that are analytically solved only for a part of the entire energy spectrum. Such models are called quasi-exactly solvable and the number of exactly determined states defines the size of the finite block matrix, which is exactly solved without any concern about the infinite block matrix. Such an example, which will be discussed in the present seminar, is the solution of the Schrödinger equation for a sextic oscillator potential with a centrifugal barrier [1]. As applications, one chose the quadrupole nuclear collective motion comprised of surface vibrations and rotations described by the Bohr model [2,3]. The radial part of the Bohr Hamiltonian, for different shapes as sphere, spheroid (prolate), triaxial (ellipsoid) and with unstable axial deformation, can be easily brought to a Schrödinger form [4,5] and therefore to the quasi-exactly solvable equation for the sextic oscillator potential [6,7,8,9,10,11,12]. Due to its special properties, the sextic potential can simulate either a spherical minimum or a deformed one, simultaneous spherical and deformed minima or a flat shape as an approximation of the infinite square well. All these features recommend it as being very suitable for the description of nuclear shape phase transitions.
1. A. G. Ushveridze, Quasi-Exatly Solvable Models in Quantum Mechanics, IOP, Bristol, 1994.
2. A. Bohr, Mat. Fys. Medd. Dan. Vid. Selsk. 26 (1952) 14.
3. A. Bohr and B. R. Mottelson, Mat. Fys. Medd. Dan. Vid. Selsk. 27 (1953) 16.
4. L. Fortunato, Eur. Phys. J. A 26 (2005) 1.
5. P. Buganu and L. Fortunato, J. Phys. G: Nucl. Part. Phys. (2016) accepted.
6. G. Levai and J. M. Arias, Phys. Rev. C 69 (2004) 014304.
7. G. Levai and J. M. Arias, Phys. Rev. C 81 (2010) 044304.
8. A. A. Raduta and P. Buganu, Phys. Rev. C 83 (2011) 034313.
9. A. A. Raduta and P. Buganu, J. Phys. G: Nucl. Part. Phys. 40 (2013) 025108.
10. P. Buganu and R. Budaca, Phys. Rev. C 91 (2015) 014306.
11. P. Buganu and R. Budaca, J. Phys. G: Nucl. Part. Phys. 42 (2015) 105106.
12. R. Budaca, P. Buganu, M. Chabab, A. Lahbas and M. Oulne, Ann. Phys. (2016) submitted.
Termodinamica sistemelor gravitationale uni-dimensionale
Dan Pirjol (IFIN-HH)
05.09.2016
Abstract:
Termodinamica sistemelor de particule interactionind prin forte gravitationale e un subiect important in astrofizica si cosmologie. Datorita proprietatii de long-range a Interactiei gravitationale, aceste sisteme au comportari diferite de cele ale sistemelor cu interactii de short-range bine studiate in mecanica statistica. Pentru sisteme cu simetrie planara, complexitatea problemei se poate reduce la studiul unui sistem echivalent uni-dimensional. Talk-ul prezinta o introducere in mecanica statistica a sistemelor gravitationale uni-dimensionale. In prezenta conditiilor periodice de frontiera, aceste sisteme prezinta tranzitii de faza care conduc la aparitia spontana a unei distributii neomogene de densitate. Un model propus recent de Miller si Rouet e analizat in detaliu, si aparitia tranzitiei de faza e demonstrata prin simulari numerice, cu rezultate in concordanta cu predictia teoretica.
Applications of multicomponent NLS equations to Bose-Einstein condensates
Vladimir S. Gerdjikov
Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, Sofia
01.09.2016
A three-component nonlinear Schrodinger-type model which describes spinor Bose-Einstein condensate ( BEC) is considered. This model is integrable by the inverse scattering method and using Zakharov-Shabat dressing method we obtain three types of soliton solutions. The multi-component nonlinear Schrodinger type models related to symmetric spaces BD.I = SO(5)/SO(3) ⊗ SO(2) is studied.
Low-energy Supersymmetry: Review and Current Status
Emilian Dudas, Ecole Polytechnique Paris
20.07.2016
Abstract:
I review the motivations for low-energy supersymmetry, the main models for supersymmetry breaking, the flavor problems that supersymmetric models generically face and the current status of supersymmetry in the light of LHC searches.
Dark matter: an historical perspective
Dr. Yann Mambrini, University of Parix XI (Orsay)
19.07.2016
Abstract:
I review in this seminar the historical evolution of the concept of "Dark Matter", from the first observations of "anomalies" in the 1930's until the development of the hypothesis of the existence of a dark halo. The presentation will be entirely based on the original historical authors, reconstructing (by their ideas but also their mistakes) the appearance of a dark side of the Universe. The talk will include discussions of original articles by Zwicky, Oort, Jansky, Gamow, Alpher, Peebles, Zeldovich, Bond and many others, opening on the prospect for the near future.
Motion of an electric charge under the action of laser fields
M Apostol, DFT
30.06.2016
Abstract
The motion of an electric charge (electron) under the action of an external electromagnetic radiation is analyzed both in the classical limit and in the quantum-mechanical theory. The classical solution is provided by the Hamilton-Jacobi equation for the mechanical action, while the quantum-mechanical solution is the well-known Volkov wavefunction. It is shown that in high-intensity radiation fields, as those generated by laser pulses, the charge can be accelerated up to ultrarelativistic velocities in a drift motion along the direction of propagation of the radiation. As a consequence of high, ultrarelativistic velocities the charge oscillations become slow and the charge does not emit radiation anymore; in addition, the ultrarelativistic charge does not "feel" anymore the radiation field. The negative-energy states get lower and lower energy, a negative momentum in the radiation field, and move in the opposite direction (as if they would possess a negative mass), such that the gap between the positive-energy and negative-energy states is increased by radiation.
Also, the motion of an electric charge (electron) is analyzed in a standing electromagnetic wave, both for a classical relativistic charge and a quantum-mechanical charge. A classical relativistic charge suffers multiple Compton collisions in a standing radiation wave. Since the usual electron flux is much lower than usual photon density (flux), the Compton collisions do not destroy the standing wave; the charge propagates almost in a straight line in the wave, with a very short mean free path; since the mean fee path is much shorter than the radiation wavelength, the charge does not "feel", practically, the radiation. For low energies, a quantum charge suffers diffraction by a standing electromagnetic wave, either by transmission, or by reflection (Kapitza-Dirac effect). In usual cases, the diffraction of the electrons by a standing radiation wave proceeds similarly as the diffraction by a classical grating.
Quantum Interferences and Correlations in Pumped Few-Level Systems
Mihai A. Macovei, Institute of Applied Physics Academy of Sciences of Moldova
Abstract:
We shall present our results on manipulation of atom-field interactions via quantum interference effects. Particularly, the output of a pumped micro-resonator containing a few-level emitter can be conveniently controlled using such phenomena. Furthermore, the spontaneous emission which occurs due to the interaction of an excited atom with the vacuum modes of the surrounding electromagnetic field reservoir can be inhibited as well. Finally, we shall describe a scheme allowing quantum correlations among a vibrating nano-mechanical resonator and an electromagnetic field mode. Quantum cooling in these systems will be shown to occur as well.
HORIZON WAVE-FUNCTION: FROM PARTICLES TO BLACK HOLES
Octavian Micu, Institutul de Stiinte Spatiale, Bucuresti-Magurele
Abstract:
Localised Quantum Mechanical particles are described by wave packets in position space, regardless of their energy. From a General Relativistic point of view, when a particles energy density is larger than a certain threshold, the particle should be a black hole. We combine these two pictures by introducing a horizon wave-function determined by the particle wave-function in position space, which is used to compute the probability that the particle is a black hole. The sources are modelled as simple Gaussian wave-packets and using the horizon wave-function formalism we calculate the probability for these particles to be Schwarzschild black holes, respectively Reissner Nordstrom black holes (in the case of charged particles). We also derive an effective Generalised Uncertainty Principle (GUP), which is obtained by adding the uncertainties coming from the two wave-functions associated to the particle.
1. Despre cartile stiintifice vechi din Biblioteca Academiei Romane, filiala Cluj-Napoca (BARFCN). 2. Cele trei exemplare ale Cartii Revolutiilor a lui Nicolai Copernic (Nurnberg, 1543) din Brasov si Cluj.
Gheorghe Stratan, IFIN-HH, Bucuresti-Magurele
Abstract:
Se descrie sumar rezultatul cercetarilor intreprinse la Cluj, constand intr-un portofoliu de cateva sute de carti din secolele XV-XVII, din care se poate reconstitui Prima Revolutie Stiintifica. Tezaurul de carte pus in evidenta este cel mai bogat din aceasta parte a Europei si necesita o protectie si o valorificare corespunzatoare. Se prezinta cateva proiecte in acest sens.
Understanding long-distance quantum correlation
Louis Marchildon, Université du Québec à Trois-Rivières
Abstract:
The interpretation of quantum mechanics (or, for that matter, of any physical theory) consists in answering the question: How can the world be for the theory to be true? That question is especially pressing in the case of the long-distance correlations predicted by Einstein, Podolsky and Rosen, and rather convincingly established during the past decades in various laboratories. I will review five different approaches to the understanding of long-distance quantum correlations: (i) the Copenhagen interpretation and some of its modern variants; (ii) Bohmian mechanics of spin-carrying particles; (iii) Everett's relative states; (iv) Cramer's transactional interpretation; and (v) the Hess-Philipp analysis of extended parameter spaces.
Highlights of the experimental program with brilliant gamma-beams at ELI-NP
Dimiter L. Balabanski
ELI-NP, IFIN-HH, Romania
Extreme Light Infrastructure – Nuclear Physics (ELI-NP) is one of the three Pan-European nuclear physics laboratories, which are at present under construction in the EU under the ESFRI scheme. At ELI-NP, high-power laser systems together with brilliant gamma beams are the main research tools. The expected performance of the ELI-NP gamma-beam system (GBS) will be reported. The emerging experimental program with brilliant gamma beams at the GBS will be presented with emphasis on the prepared day-one experiments and the related instruments designed for their realization.
Novel Features of Josephson Junctions under External Electromagnetic
Radiation
Yu. M. Shukrinov
BLTP, JINR, Dubna
Dubna University, Dubna
Abstract:
External electromagnetic radiation leads to the series of interesting effects as in case of single Josephson junction and in case of coupled system of junctions. We discuss here its effect on the dynamics of Josephson junction shunted by LC circuit. When the Josephson frequency is equal to the frequency of the formed circuit, additional stable branch appears in the IV -characteristic of the junction. We show that the amplitude dependence of the Shapiro step width crucially changes when the Shapiro step is on the resonant circuit branch. This effect might give the important advantages for methods and technologies that exploit the response of Josephson junctions to microwave fields [1]. Interesting features appear in the intrinsic Josephson junctions in high temperature superconductors related to the charging of the superconducting layers in the bias current interval corresponding to the Shapiro steps. We show that the longitudinal plasma wavelength is changingby the changing of the power of external radiation [2] and discuss
possible applications of this effect.
It was found that the observed Shapiro step subharmonics in the IV characteristics coincide precisely with a continued fraction sequence [3]. The algorithm for the appearance and detection of subharmonics with increasing radiation amplitude is discussed. The staircase structures registered in many well-known experiments and simulations may also form a continued fraction sequence. Variation of Josephson junction parameters leads to the structured chaos [4]. Another type of staircase structure of Shapiro steps [5] is found in the branching region. Its origin is related to the coupling between junctions and their switching from rotating to oscillating states. Experimental observation of this type of staircase structure would provide conclusive proof of the coupling between junctions
and a way for precise measurement of its value.
References
1. Yu. M. Shukrinov, I. R. Rahmonov, K. V. Kulikov, P. Seidel, EPL, 110, 47001 (2015).
2. Yu. M. Shukrinov, I. R. Rahmonov, M. A. Gaafar, Phys. Rev. B, 86, 184502 (2012).
3. Yu. M. Shukrinov, A. E. Botha, S. Yu. Medvedeva, M. R. Kolahchi, A. Irie, Chaos, 24, 033115 (2014).
4. Yu. M. Shukrinov, S. Yu. Medvedeva, A. E. Botha, M. R. Kolahchi, and A. Irie, Phys. Rev.B, 88, 214515 (2013).
5. Yu. M. Shukrinov, I. R. Rahmonov, Majed Nashaat, Pis’ma v ZhETF, 102, 919 (2015).
An attractive critical point from weak antilocalization on fractals.
Doru Sticlet, Delft University of Technology
The one-parameter scaling theory of localization describes the behavior of disordered systems in integer dimensions. We test its limits for systems with non-integer dimensions by studying conduction on fractal lattices with disorder. Notably, we demonstrate a new effect for symplectic Hamiltonians living on certain fractal families with Hausdorff dimension lower than two. Analytical arguments and numerical simulations show that weak antilocalization corrections induce an attractive critical point with a scale-invariant conductance. This phenomenon is not seen in integer dimension lattices, which have at most a single repulsive critical point, marking the metal-insulator transition.
Referinta: D. Sticlet and A. Akhmerov, arXiv:1510.02096.
Dinamica (super)-solitonilor şi integrabilitate pe reţele discrete
Nicoleta Corina Babalîc
Conceptele de soliton şi integrabilitate sunt două dintre noţiunile frecvent întâlnite în procesele evolutive neliniare. Din 1834, când John Scott Russel a observant o undă de translaţie solitară, foarte stabilă într-un canal cu apă puţin adânc din Scoţia şi până astăzi, solitonul s-a impus printre subiectele de interes ale cercetătorilor preocupaîi de dinamica neliniară şi fizica teoretică în general, iar integrabilitatea a devenit practic un nou domeniu din fizica matematică, care are legatură cu toate domeniile fundamentale ale matematicii.
În acest seminar, pornind de la versiuni semidiscrete integrabile ale mai multor ecuaţii de evoluţie neliniare (semidiscret KdV şi semidiscret Volterra bidirectional cu două componente), vom construi ecuaţii discrete complet integrabile aplicând metoda directă a biliniarizării (formalismul Hirota). Complet integrabilitatea va fi demonstrată prin construcţia soluţiei N-solitonice.
Extinzănd formalismului biliniar în context supersimetric vom prezenta, în partea a doua, dinamica solitonilor supersimetrici într-un sistem care generalizează cazurile super-KdV şi super-mKdV într-o singură ecuaţie anume ecuaţia Gardner supersimetrică. Aspectul nou este nu numai o dinamică nouă a supersolitonilor (care prezintă o interacţie ne-elastică în superspaţiu), dar şi existenţa supersolitonilor slab localizaţi, care în acest caz depind de parametrii fermionici liberi.
