1,243 research outputs found

    Spontaneous symmetry breaking in the linear sigma model at finite chemical potential: One-loop corrections

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    We investigate spontaneous symmetry breaking within the linear sigma model with the SU(2)xU(1) internal symmetry at finite chemical potential, which was suggested as a model for kaon condensation in the CFL phase of dense quark matter. One-loop corrections to the scalar field effective potential as well as its propagator are calculated. Particular attention is paid to the type-II Goldstone boson that appears in the Bose--Einstein condensed phase. Furthermore, we show that the type-I Goldstone boson -- the superfluid phonon -- is allowed to decay due to the nonlinearity of its dispersion relation at high momentum, and determine its decay width.Comment: 13 pages, REVTeX4, 37 eps figures; v2: substantial error in Sec. IV corrected, references added, other minor corrections; version to appear in Phys. Rev.

    Two-color quark matter: U(1)_A restoration, superfluidity, and quarkyonic phase

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    We discuss the phase structure of quantum chromodynamics (QCD) with two colors and two flavors of light quarks. This is motivated by the increasing interest in the QCD phase diagram as follows: (1) The QCD critical point search has been under intensive dispute and its location and existence suffer from uncertainty of effective U(1)_A symmetry restoration. (2) A new phase called quarkyonic matter is drawing theoretical and experimental attention but it is not clear whether it can coexist with diquark condensation. We point out that two-color QCD is nontrivial enough to contain essential ingredients for (1) and (2) both, and most importantly, is a system without the sign problem in numerical simulations on the lattice. We adopt the two-flavor Nambu-Jona-Lasinio model extended with the two-color Polyakov loop and make quantitative predictions which can be tested by lattice simulations.Comment: 14 pages, REVTeX4, 12 eps figures; v2: version published in Phys. Rev. D; v3: an error in the Appendix fixed, Fig. 9 modified accordingl

    Aesthetic satisfaction in lip and palate clefts: a comparative study between secondary and tertiary bone grafting

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    Lip and palate cleft represent one of the most frequently occurring congenital deformity, which includes dental anomalies, such as variation in tooth number and position. In case of hypodontia implant-prosthetic rehabilitation offers significant advantages in terms of function, aesthetics and quality of life and bone graft is usually needed. Secondary bone grafting, generally performed in the mixed dentition phase (years 8-11) seems to be the most successful method to allow for rehabilitation. It's often necessary to perform a tertiary bone grafting in adult age in order to achieve better bone quantity and quality before implant placement. Aim of this retrospective study was to evaluate the aesthetic perception that patients had of themselves comparing dental implants placed in tertiary grafted alveolar cleft sites with a previous secondary grafting to only secondary grafting. Between 2009 and 2012, fourteen alveolar cleft were treated with implant rehabilitation and eleven of them received tertiary bone grafting six months prior to implant placement. All patients were questioned to give a score from 1 to 10 their aesthetic satisfaction of their smile before and after implant rehabilitation and during pre-surgery provisional rehabilitation. At the end of their prosthesis rehabilitation patients who received tertiary bone grafting resulted more satisfied than those who had secondary bone grafting only (9.5 vs 8)

    Gingival hyperplasia around dental implants in jaws reconstructed with free vascularized flaps: a case report series

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    Free vascularized flaps are the gold standard for reconstruction of the facial skeleton after surgical ablation of pathologies or when important atrophy of the jaws exists. A frequent problem seen during prosthetic rehabilitation after reconstruction with free vascularized flaps is the onset of hyperplastic granulomatous reactive tissue around the prosthetic abutment of the implant. The features of this phenomenon seem to be directly related to the characteristics of the periimplant tissue and of the manufacturing materials of the prosthesis and abutments. This complication can be seen quite often; we found it in 7 of 40 patients (17.5%). It does not seem to significantly affect the survival rate of implants. The aim of the study was to analyze the behavior of such lesions and to suggest our clinical approach with the management of these kinds of patients and complications. To remove gingival hyperplasia, we used either a traditional cold scalpel or an electric cautery or laser. We had good results using these tools. The onset of this phenomenon was not influenced by either the kind of implant and free flaps used or by the local conditions of the patients (such as radiotherapy). The number of recurrences was highly influenced by the oral hygiene of the patients

    Spontaneous breaking of continuous translational invariance

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    Unbroken continuous translational invariance is often taken as a basic assumption in discussions of spontaneous symmetry breaking (SSB), which singles out SSB of translational invariance itself as an exceptional case. We present a framework which allows us to treat translational invariance on the same footing as other symmetries. It is shown that existing theorems on SSB can be straightforwardly extended to this general case. As a concrete application, we analyze the Nambu-Goldstone modes in a (ferromagnetic) supersolid. We prove on the ground of the general theorems that the Bogoliubov mode stemming from a spontaneously broken internal U(1) symmetry and the longitudinal phonon due to a crystalline order are distinct physical modes.Comment: 14 pages, 4 pdf/jpg figures, REVTeX 4.1; v2: section IV expanded, new appendix and references added, numerous other minor modifications throughout the tex

    Histological and immunohistochemical evaluation of mandibular bone tissue regeneration

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    The purpose of the study was to perform an immunohistochemical and histological evaluation of samples taken from different bone regeneration procedures in atrophic human mandible. 30 patients (15 men and 15 women, age range of 35-60 years), non-smokers, with good general and oral health were recruited in this study and divided into three groups. The first group included patients who were treated with blood Concentration Growth Factors (bCGF), the second group included patients who were treated with a mixture of bCGF and autologous bone, while the third group of patients was treated with bCGF and tricalcium phosphate/hydroxyapatite (TCP-HA). Six months after the regenerative procedures, all patients undergone implant surgery, and a bone biopsy was carried out in the site of implant insertion. Each sample was histologically and immunohistochemically examined. Histological evaluation showed a complete bone formation for group II, partial ossification for group I, and moderate ossification for group III. Immunohistochemical analysis demonstrated a statistically significant difference between the three groups, and the best clinical result was obtained with a mixture of bCGF and autologous bone

    Monolithic zirconia and digital impression: case report

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    The aim of this study is to present a clinical case of a full arch prosthetic rehabilitation on natural teeth, combining both digital work-flow and monolithic zirconi

    Electron-impact ionization of atomic hydrogen at 2 eV above threshold

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    The convergent close-coupling method is applied to the calculation of fully differential cross sections for ionization of atomic hydrogen by 15.6 eV electrons. We find that even at this low energy the method is able to yield predictive results with small uncertainty. As a consequence we suspect that the experimental normalization at this energy is approximately a factor of two too high.Comment: 10 page

    Magneto-optics of massive Dirac fermions in bulk Bi2Se3

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    We report on magneto-optical studies of Bi2Se3, a representative member of the 3D topological insulator family. Its electronic states in bulk are shown to be well described by a simple Dirac-type Hamiltonian for massive particles with only two parameters: the fundamental bandgap and the band velocity. In a magnetic field, this model implies a unique property - spin splitting equal to twice the cyclotron energy: Es = 2Ec. This explains the extensive magneto-transport studies concluding a fortuitous degeneracy of the spin and orbital split Landau levels in this material. The Es = 2Ec match differentiates the massive Dirac electrons in bulk Bi2Se3 from those in quantum electrodynamics, for which Es = Ec always holds.Comment: 5 pages, 3 figures and Supplementary materials, to be published in Physical Review Letter
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