Fission channels around emitted magic numbers
Nafiseh Shayan Shakib, R. A. Gherghescu, D. N. Poenaru
IFIN-HH / DFT
Abstract:
Fission is calculated within the macroscopic-microscopic method. Some different channels around the emitted magic numbers are investigated. The macroscopic-microscopic method is employed for the deformation energy. The microscopic potential is of the deformed two-centre type, yielding the evolution of proton and neutron level schemes from one parent to two completely separated fragment nuclei. The shell corrections are calculated using the two single-particle levels by the Strutinsky method. The total deformation energy is obtained as the liquid drop and the shell correction energy sum. Minimisation of the action integral and the WKBmethod are used to get the penetrabilities and lifetimes.
Keywords: Strutinsky Method- macroscopic-microscopic method- Fission- Liquid Drop Model- Two- Centre Shell Model.
Diagrama de faza a cromodinamicii cuantice
Marian Apostol
DFT / IFIN-HH
Abstract
It is suggested that the hadronization of the quark-gluon plasma is a first-order phase transition described by a critical curve in the temperature-(quark) density plane which terminates in a critical point. Such a critical curve is derived from the van der Waals equation with zero pressure and its parameters are estimated by using the theoretical approach given in M. Apostol, Roum. Reps. Phys. 59 249 (2007). The main assumption is that quark-gluon plasma created by high-energy nucleus-nucleus collisions is a gas of (massless) ultrarelativistic quarks at equilibrium with gluons (vanishing chemical potential, indefinite number of quarks). This plasma expands, gets cool and dilute, and hadronizes at a certain transition temperature and transition density. The transition density is very close to the saturation density of the nuclear matter and, it is suggested that both these points are very close to the critical point. This point is given by n=1fm-3 and T=200MeV and it can have a universal character.
Exotic resonant states for 1D twin complex square potentials. Subluminal and superluminal traversal times
Nicolae Grama
DFT / IFIN-HH
Abstract:
The natural modes for 1D twin square potentials of complex strength g are studied. A global analysis of the natural modes based on the construction of the Riemann surfaces RIg and RIIg of the multiple valued function k = k(g), where k(g) defines the poles of the transmission coefficient, is done. To each nonradiative or radiative mode a sheet of the Riemann surface is associated. All the natural modes of the system are identified and treated in a unified way. New classes of resonant state poles with exotic properties are identified on the k-plane images of the sheets of RIg and RIIg and the properties of the exotic modes are studied. The traversal time through the 1D twin square potentials is analysed. Subluminal and superluminal traversal times are evidenced. An approximate formula for the frequencies k for which the maximal superluminal velocities are gained as a function of the potential parameters is given.
New developments in minimal gauged supergravities in 5 dimensions
Cristina Rugina
IFIN-HH / DFT
We investigate the hidden symmetries of the Kerr-Newman, of the D=5 minimal gauged supergravity which admits a Killing-Maxwell system in the sense of Carter and of higher dimensional spacetimes in the presence of Killing-Yano torsion. We note that when an electromagnetic tensor is present and an associated Killing-Maxwell system can be constructed in the sense of Carter, the Killing-Maxwell field becomes a PCKY (primary conformal Killing-Yano) tensor or a PGCKY (primary generalized conformal Killing-Yano) tensor, the latter in the presence of torsion. We point out the structure of the Dirac-type operators of the spinning point particle in arbitrary- dimensional spacetimes with torsion, focusing on the case when torsion can be assimilated with a Killing-Yano tensor and these spacetimes are endowed with towers of Killing-Yano tensors, and hence we show the anomalies of these additional supersymmetries cancel out in this particular case. Also we prove the equivalence between a closed conformal Killing-Yano tensor and a Killing spinor for arbitrary dimensional Sasaki-Einstein manifolds and we explicitly construct a Killing spinor for a specific 5 dimensional minimal gauged supergravity solution that is endowed with a Sasaki structure deformed by torsion.
Relativistic resonance fluorescence
Octavian Postavaru
DFT / IFIN-HH
Abstract:
Resonance fluorescence is a fundamental phenomenon of quantum optics. During this process, electromagnetic radiation is emitted by a substance that has absorbed electromagnetic radiation. A typical emission spectrum exhibits three peaks, with the central peak being centered at the laser frequency. In this work, we show that the structure of the relativistic spectra is different from the non-relativistic one due to the spin-orbit interaction and the velocity-dependent electron mass only accounted for in the relativistic theory. The bare atomic states are solution of the Dirac equation rather than Schrodinger's equation. Our formalism goes beyond the long-wavelength dipole approximation and takes into account non-dipole effects of retardation and interaction with magnetic components of the field. The resonance spectrum depends on the relativistic magnetic sub-levels of the atom, leading to a complex splitting of the usual three-peak fluorescence structure. This inherent systematic effect must be considered in fluorescence spectroscopy.
Reactii exotice cu schimb de sarcina
Andrei Neacsu
DFT / IFIN-HH
In aceasta lucrare sunt aduse contributii la studiul teoretic al DBD. S-au dezvoltat metode si coduri numerice noi pentru calculul factorilor spatiu faza (PSFs)si al elementelor de matrice nucleara (NMEs) ce apar in formulele timpilor de viata pentru DBD. Pentru calculul PSFs a fost dezvoltat un cod numeric care foloseste functii electronice relativiste pentru descrierea electronilor rezultati din dezintegrare. Pentru obtinerea acestora s-au luat in considerare efectele de ecranare coulombiana si de dimensiune nucleara finita si s-a folosit un potential Coulombian dedus dintr-o distributie realista a protonilor in nucleul fiica. Au fost calculati PSFs pentru DBD cu si fara emisie de neutrini, pentru tranzitii pe stari fundamentale si pe stari excitate 2+, 0+. Pentru calculul NME s-a construit un cod nou de calcul, bazat pe modelul in paturi de structura nucleara, care reduce substantial timpul de calcul al elementelor de matrice ale operatorilor biparticula ai DBD (TBMEs). Apoi au fost calculate NME atat pentru mecanismul de producere a DBD fara neutrini, prin schimb de neutrini Majorana usori intre 2 nucleoni din nucleu, cat si pentru mecanismul de schimb de neutrini Majorana grei. De asemenea, s-a facut un studiu sistematic al influentei pe care diferitele efecte nucleare si parametri de model, luati in considerare in calcul, o au asupra valorilor finale ale NME.
M2 brane potentials in M-theory compactifications to 3 dimensions
Andrei Micu
IFIN-HH / DFT
In type IIB and F-theory models, various efects which are needed for low energy phenomenology induce a potential for D3 branes. Such effects are not understood on the dual M-theory side and we propose a resolution to this puzzle by studying the most general M-theory compactifications to 3 dimensions.
Constraints on the high density dependence of the symmetry energy from heavy-ion collisions
Dr. Dan Cozma (DFH - IFIN-HH)
An isospin dependent version of the quatum molecular dynamics (QMD) transport model is employed to study the influence of the isospin dependent part of the equation of state (asy-EoS) of nuclear matter on the dynamics of intermediate energy heavy-ion collisions. We find that neutron-proton elliptic flow difference (or alternatively neutron-proton elliptic flow ratio) provides the opportunity to constrain the high-density dependence of the symmetry energy as its dependence on uncertain model parameters like compressibility modulus and in-medium nucleon-nucleon cross-sections is mild while dependence on asy EoS is pronounced [1]. Recent experimental results of the FOPI-LAND collaboration [2] are employed to constrain the high density dependence of the symmetry energy to a moderately stiff one. Influences due to different parametrizations of the asy-EoS and type of the transport model employed on the result are presented [3], allowing the extraction of an almost model independent constraint. Results and problems of employing other observables (e.g. pi-/pi+ multiplicity ratios) are also discussed.
References:
1. M.D. Cozma, Physics Letters B700, 139 (2011);
2. P. Russotto et al., Physics Letters B687, 471 (2011);
3. M.D. Cozma et al. , arXiv:1305.5417 [nucl-th].
Proton-neutron pairing correlations in atomic nuclei
Daniel Negrea, DFT/IFIN-HH
Abstract
The common understanding of proton-neutron pairing, whose fingerprints are currently investigated in N = Z nuclei, relies on Cooper pair mechanism and BCS-type models. In the present thesis we present an alternative approach which, contrary to BCS models, conserves exactly the particle number and the isospin. In this approach the ground state of N=Z nuclei is described as a condensate of alpha-like quartets built by two neutrons and two protons coupled to the total isospin T=0 and total spin J=0. The comparison with exact shell model calculations shows that the quartet condensation model (QCM) gives a very accurate description of pairing correlations in N=Z nuclei, much better than the BCS models. It is also shown that proton-neutron pairing and alpha-type condensation are important not only for N=Z nuclei but also for nuclei with excess neutrons. In the latter case the condensate of alpha-like quartets coexist with the condensate of the neutron pairs in excess relative to the N=Z isotope. Using the framework of QCM we have also studied the competition between the isovector and the isoscalar proton-neutron pairing in nuclei with N=Z. Our results indicate that the contribution of isoscalar pairing to the ground state pairing correlations is very small compared to the isovector pairing.
Evolutia formei nucleare de-a lungul lantului izotopic al Platinei
Dr. Petrica Buganu, IFIN-HH/DFT
Lantul izotopic 180-196Pt a fost analizat cu modele exact solubile pentru variabilele cvadrupolare intrinseci cu scopul de observa o coexistenta a formelor nucleare, cat si o evolutie de la forma prolate la cea oblate prin forma triaxiala. In plus, au fost efectuate calcule numerice pentru spectrul energetic corespunzator benzilor fundamentala, beta si gamma si probabilitatile de tranzitie E2 intre stari apartinand acestor benzi si comparate cu datele experimentale corespunzatoare fiecarui nucleu.
Quantum systems under frequency modulation
Dr. Sorin Paraoanu
O.V. Lounasmaa Lab, Aalto University, Finland
We consider a superconducting circuit consisting of a capacitively-shunted charge qubit (a transmon) embedded in a superconducting waveguide resonator. Two microwave fields are applied to the system: one, at the frequency of the resonator, is used for measurement, while the other, around the Larmor frequency of the qubit, is used to drive the qubit. In addition, the qubit frequency is modulated by a random telegraph noise with externally-controlled amplitude and characteristic jumping frequency. Surprisingly, by adding noise in this way a new, motional averaged spectral line is formed with a linewidth smaller than the amplitude of the random modulation [1]. We have also succeeded in driving Rabi oscillations on the motional averaged line, demonstrating the formation of hybrid states of the transmon and modulation field, with transitions that can be coherently driven.
When modulating the system sinusoidally, we observe a rich spectral structure, resembling a Landau-Zener interference pattern. However, direct Landau-Zener transitions are prohibited in our system by the fact that the frequency of the modulation is much smaller than the energy level separation. We show that in this case the transitions occurthrough the absorption of photons from the driving field; we call this process photon-assisted Landau-Zener effect.
For the values of the fields used in our experiment we show that, in a rotating frame, the system reaches the ultrastrong coupling regime. Our setup can also be seen as the simulation of the effect of coupling an externally-controlled fluctuation to a qubit. We anticipate that the experimental demonstration of motional averaging presented in this work will provide a novel route to improving the dephasing times of existing superconducting qubits.
REFERENCES
1. J. Li, M. P. Silveri, K. S. Kumar, J.-M. Pirkkalainen, A. Vepsäläinen, W. C. Chien, J. Tuorila, M. A. Sillanpää, P. J. Hakonen, E. V. Thuneberg, and G. S. Paraoanu, "Motional averaging in asuperconducting qubit", Nat. Commun. Vol. 4, 1420 (2013).
On the Super-Renormalizability of Gauge Models
Dan-Radu Grigore
DFT/IFIN-HH
There is a some bound on the ultra-violet limit of quantum perturbative theories given by the power counting theorem. We study the possibility that gauge models behave better than predicted by power counting in the ultra-violet limit. The analysis is done in orders 2 and 3 of the perturbation theory using the causal approach of Epstein and Glaser.
An Exploration of the Singularities in General Relativity
Drd. Ovidiu Cristinel Stoica
Universitatea Politehnica Bucuresti
Faculty of Applied Sciences, Department of Mathematics-Informatics
This work presents the foundations of Singular Semi-Riemannian Geometry and Singular General Relativity, based on the author's research. An extension of differential geometry and of Einstein's equation to singularities is reported. Singularities of the form studied here allow a smooth extension of the Einstein field equations, including matter. This applies to the Big-Bang singularity of the FLRW solution. It applies to stationary black holes, in appropriate coordinates (since the standard coordinates are singular at singularity, hiding the smoothness of the metric). In these coordinates, charged black holes have the electromagnetic potential regular everywhere. Implications on Penrose's Weyl curvature hypothesis are presented. In addition, these singularities exhibit a (geo)metric dimensional reduction, which is thought to act as a regulator for the quantum fields, including for quantum gravity, in the UV regime. This opens the perspective of perturbative renormalizability of quantum gravity without modifying General Relativity.
[1] On Singular Semi-Riemannian Manifolds, http://arxiv.org/abs/1105.0201
[2] Warped Products of Singular Semi-Riemannian Manifolds, http://arxiv.org/abs/1105.3404
[3] Schwarzschild Singularity is Semi-Regularizable, Eur. Phys. J. Plus, 127(83):1-8, 2012, http://arxiv.org/abs/1111.4837
[4] Analytic Reissner-Nordstrom Singularity, Phys. Scr., 85(5):055004,2012, http://arxiv.org/abs/1111.4332
[5] Beyond the Friedmann-Lemaitre-Robertson-Walker Big Bang singularity, Commun. Theor. Phys., 58(4):613-?616, March 2012, http://arxiv.org/abs/1203.1819
[6] An. St. Univ. Ovidius Constanta (2012) vol. 20(2), 213-238, http://www.anstuocmath.ro/mathematics/pdf26/Art16.pdf, http://arxiv.org/abs/1108.5099
[7] An Exploration of the Singularities in General Relativity, http://arxiv.org/abs/1207.5303
Non-Commutative Algebroid Ricci Flows, Modified Gravity, & Deformation Quantization
CS1 Dr. Sergiu I. Vacaru
Alexandru Ioan Cuza University, UAIC, Iasi, Romania
We survey our recent research on commutative and noncommutative Ricci flows with Lie algebroid symmetries and nonholonomic distributions determined by (effective) Lagranians and/or generic off-diagonal metrics. There are provided (non) commutative versions of Grigory Perelman’s functionals and discussed possible implications of such geometric thermodynamic type values in nonlinear diffusion and quantum information processes.
Stationary configurations of non-Riemannian geometric flows result in nonholonomic Ricci solitons (in particular, generalized Einstein spaces) related to modified theories of gravity. For various classes of generic off—diagonal solutions, we can model physical effects (for instance) in massive gravity and/or Horava-Lifshits type theories. It is summarized the anholonomic deformation method of construting exact solutions with generalized Lie symmetris (algebroid, solitonic, noncommutative and other types).
Reformulating the geometric and classical physical models in almost Kaehler variables, we can apply methods of deformation quantization, geometric A—brane quantization and/or gauge like gravity techniques. The approaches can be extended to noncommutative variables in the A. Connes approach (in our case, with spectral functionals/triples and generalized Dirac operators), or with almost symplectic noncommutative deformations. Finally, we speculate on perspectives of above mentioned geometric and quantum methods in modern gravity and cosmology.
Recent review: S. Vacaru, http://arxiv.org/pdf/1204.5387.pdf
Web Page: http://www.uaic.ro/uaic/bin/view/Research/AdvancedTheoretical
Sursa de fotoni corelaţi cuantic şi sistemul pentru măsurarea lor, realizate la IFIN-HH
Prezintă: Dr. ing. Alexandru Rusu, alrusu@ifin.nipne.ro.
O activitate desfăşurată în DFNA oferă un model funcţional-constructiv pentru un generator de fotoni corelaţi cuantic produşi prin fenomenul „spontaneous down conversion” (SPDC) şi prototipul unui sistem pentru detecţia şi numărarea lor.
Se vor aminti caracteristici ale fenomenului SPDC, ale fascicolelor de fotoni generate prin acest fenomen, pentru a justifica componenţa generatorului şi alegerea criteriilor de identificare a fotonilor produşi. Urmează prezentarea rezultatelor care dovedesc că fascicolele măsurate sunt formate din fotoni corelaţi cuantic.
O aplicaţie a generatorului, interesantă prin aceea că sugerează existenţa unui mecanism pentru stimularea fenomenului SPDC, semnalează nevoia de noi experienţe şi de modelul explicativ. Datele ce vor fi prezentate pot stârni interesul.
Realizarea instrumentului „single photon detector” implică identificarea şi măsurarea unor „parametri ascunşi” ai fotodiodei cu avalanşă, rezolvarea unor probleme de tehnica frigului, de optica, de mecanică, de programare; un şir de oscilograme vor fi convingătoare.
"Mini-Workshop on Quantum Optics and Quantum Information (QOQI)"
Organizator: Dr. Aurelian Isar
Joi 11.04.2013 - Sala de seminar DFT
10.00 - 10.10 Opening
10.10 - 10.50 Vladimir I. Man'ko (P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia) Probability instead of the wave function in conventional quantum mechanics
10.50 - 11.20 Margarita A. Man'ko (P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia) Tomographic entropy and information for classical and quantum states
11.20 - 11.30 Coffee break
11.30 - 12.00 Vladimir A. Andreev (P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia) Inverse scattering transformation method in quantum optics
12.00 - 12.30 Paulina Marian (Univ. Bucharest) Decay of non-classicality for one-mode non-Gaussian states
12.30 - 13.00 Radu Ionicioiu (Dept. Theor. Phys., NIPNE) Entangling by measurement: the generalized parity box
13.00 - 13.30 Lunch break
13.30 - 14.10 Vladimir I. Man'ko Star product formalism and tomographic probability representation of quantum mechanics and quantum optics
14.10 - 14.40 Iulia Ghiu (Univ. Bucharest) Quantum Chernoff bound as a measure of quantum degree of polarization
14.40 - 14.50 Coffee break
14.50 - 15.20 Vladimir A. Andreev The correlation Bell inequalities
15.20 - 15.50 Aurelian Isar (Dept. Theor. Phys., NIPNE) Quantum correlations in two-dimensional Gaussian open quantum systems
15.50 - 16.10 Serban Suciu (Univ. Bucharest & Dept. Theor. Phys., NIPNE) Many-to-many teleportation based on non-maximally entangled states
16.10 Closing
Strong-field Relativistic Processes in Highly Charged Ions
Dr. Octavian Postavaru
IFIN-HH
In this presentation we investigate strong-field relativistic processes in highly charged ions. In the first part, we present resonance fluorescence of laser-driven highly charged ions in the relativistic regime by solving the time-dependent master equation in a multi-level model. Our ab initio approach based on the Dirac equation allows for investigating highly
relativistic ions, and, consequently, provides a sensitive means to test correlated relativistic dynamics, bound-state quantum electrodynamic phenomena and nuclear effects by applying coherent light with x-ray frequencies. Atomic dipole or multipole moments may be determined to unprecedented accuracy by measuring the interference-narrowed fluorescence spectrum. Furthermore, we investigate the level structure of heavy hydrogenlike ions in laser beams. Interaction with the light field leads to dynamic shifts of the electronic energy levels, which is relevant for spectroscopic experiments. We apply a fully relativistic description of the electronic states by means of the Dirac equation. Our formalism goes beyond the dipole approximation and takes into account non-dipole effects of retardation and interaction with the magnetic field components of the laser beam. We predicted cross sections for the inter-shell trielectronic recombination (TR) and quadruelectronic recombination processes which have been experimentally confirmed in electron beam ion trap measurements, mainly for C-like ions, of Ar, Fe and Kr. For Kr30+, inter-shell TR contributions of nearly 6% to the total resonant photorecombination rate
were found.
http://archiv.ub.uni-heidelberg.de/volltextserver/11427/
Factori de forma hadronici la energii joase
Raport de faza Nucleu
Dr. Irinel Caprini
Departamentul de Fizica Teoretica
IFIN-HH
In cadrul fazei s-au dezvoltat metode teoretice specifice regimului neperturbativ al cromodinamicii cuantice pentru studiul factorului de forma electromagnetic al mezonului pi si s-a obtinut o determinare precisa, independenta de model, a parametrilor care descriu distributia de sarcina a acestuia. Rezultatele sunt relevante pentru testarea modelului standard al particulelor si detectarea unor posibile semnale ale fizicii dincolo de modelul standard in cazul momentului magnetic anomal al muonului.
Multi-center Taub-NUT almost-BPS solutions
Referat de doctorat
Cristina Rugina (DFT)
Microstates of colinear black holes embedded in a multi-center Taub-NUT spacetime are sought in 4 dimensions. A set of coupled ordinary partial differential equations are obtained and solved for almost-BPS states, where some supersymmetry is preserved in the context of N=2 supergravity in 4 dimensions. The regularity of solutions is being carefully considered and we ensure that no CTC (closed time-like curves) are present. The larger framework is that of 11-dimensional N=2 supergravity and the current theory is obtained by compactifying down to 4 dimensions.
Quantum theory of an open-cavity laser considering two spectrally overlapping modes
in collaboration with Sergey Skipetrov and Miguel Orszag
Facultad de Física, Pontificia Universidad Católica de Chile, Santiago
E-mail: veremeev "at" fis.puc.cl
I will present our recent results [1] concerning the problem of open-cavity laser. The openness of the cavity is described by a non-diagonal damping matrix, hence the spectral overlapping between the resonator modes is present. For this system we develop the quantum theory assuming that only two modes compete for the gain. We show that the modes interact to build up a collective mode that becomes the lasing mode when pumping exceeds a threshold. This collective mode exhibits all the features of a typical laser mode, whereas its precise behavior depends explicitly on the openness of the cavity. One of the possible applications of our theory may lie in the field of random lasers (RL) [2]. In a RL the lasing appears as an effect of gain combined with multiple scattering in a disordered material. Compared to the traditional laser system the RL doesn't require the presence of an optical resonator.
References:
1. V. Eremeev, S. E. Skipetrov and M. Orszag, Phys. Rev. A 84 (2011), 023816.
2. Nano and Random Lasers, special issue of J. Opt. 12, 2 (2010); D. S. Wiersma, Nature Phys. 4,
359 (2008).
Generalised Killing-Yano Symmetry and Supergravity Black Holes
Dr. Tsuyoshi Houri
Osaka City University, Japan
and
DAMTP Cambridge UK
Killing-Yano symmetry has played an important role in the study of black hole physics. For instance, it serves as the most fundamental symmetry in the Kerr spacetime in the sense that the symmetry generates isometries. In this talk, we start with reviewing why the Killing-Yano symmety is important in vacuum black hole spacetimes, especially in higher dimensions, and explain that in the context of supergravities the notion of Killing-Yano symmetry is generalised in a natural way. It is also shown that a lot of exact solutions in supergravities which are describing charged, rotating balck holes admit the generalised Killing-Yano symmetry. Finally we attempt to classify spacetimes admitting the symmetry and obtain general expressions of the metrics.
References: arXiv:1004.1032, 1104.0852 and 1203.0393
