Supersymmetric Extension of the Lorentz and CPT-Violating Maxwell-Chern-Simons Model

Focusing on gauge degrees of freedom specified by a 1+3 dimensions model hosting a Maxwell term plus a Lorentz and CPT non-invariant Chern-Simons-like contribution, we obtain a minimal extension of such a system to a supersymmetric environment. We comment on resulting peculiar self-couplings for the gauge sector, as well as on background contribution for gaugino masses. Furthermore, a non-polynomial generalization is presented.Comment: revtex4, 4 pages, no figure

Superheavy Dark Matter with Discrete Gauge Symmetries

We show that there are discrete gauge symmetries protect naturally heavy X particles from decaying into the ordinary light particles in the supersymmetric standard model. This makes the proposal very attractive that the superheavy X particles constitute a part of the dark matter in the present universe. It is more interesting that there are a class of discrete gauge symmetries which naturally accommodate a long-lived unstable X particle. We find that in some discrete Z_{10} models, for example, a superheavy X particle has lifetime \tau_X \simeq 10^{11}-10^{26} years for its mass M_X \simeq 10^{13}-10^{14} GeV. This long lifetime is guaranteed by the absence of lower dimensional operators (of light particles) couple to the X. We briefly discuss a possible explanation for the recently observed ultra-high-energy cosmic ray events by the decay of this unstable X particle.Comment: 9 pages, Late

Quantum Theory of Noncommutative Fields

Generalizing the noncommutative harmonic oscillator construction, we propose a new extension of quantum field theory based on the concept of "noncommutative fields". Our description permits to break the usual particle-antiparticle degeneracy at the dispersion relation level and introduces naturally an ultraviolet and an infrared cutoff. Phenomenological bounds for these new energy scales are given.Comment: LaTeX file, JHEP3.cls, subequations.sty; 12 pages, no figures. Final version published in JHEP with some references adde

Instant preheating mechanism and UHECR

Top-down models assume that the still unexplained Ultra High Energy Cosmic Rays (UHECR's) are the decay products of superheavy particles. Such particles may have been produced by one of the post-inflationary reheating mechanisms and may account for a fraction of the cold dark matter. In this paper, we assess the phenomenological applicability of the simplest instant preheating framework not to describe a reheating process, but as a mechanism to generate relic supermassive particles as possible sources of UHECR's. We use cosmic ray flux and cold dark matter observational data to constrain the parameters of the model.Comment: 7 pages, 2 figures, submitted to PR

Spontaneous Lorentz Violation via QED with Non-Exact Gauge Invariance

We reconsider an alternative theory of the QED with the photon as a massless vector Nambu-Goldstone boson and show that the underlying spontaneous Lorentz violation caused by the vector field vacuum expectation value, while being superficial in gauge invariant theory, becomes physically significant in the QED with a tiny gauge non-invariance. This leads, through special dispersion relations appearing for charged fermions, to a new class of phenomena which could be of distinctive observational interest in particle physics and astrophysics. They include a significant change in the GZK cutoff for UHE cosmic-ray nucleons, stability of high-energy pions and W bosons, modification of nucleon beta decays, and some others.Comment: 15 pages, to appear in Eur.Phys.J.

SUSY Resonances from UHE neutralinos in Neutrino Telescopes and in the Sky

In the Top-down scenarios, the decay of super-heavy particles (m~10^{12-16}GeV), situated in dark-matter halos not very far from our Galaxy, can explain the ultra-high-energy (UHE) cosmic-ray spectrum beyond the Griesen-Zatasepin-Kuzmin cut-off. In the MSSM, a major component of the UHE cosmic-ray flux at PeV-EeV energies could be given by the lightest neutralino \chi, that is the lightest stable supersymmetric particle. Then, the signal of UHE \chi's on earth might emerge over the interactions of a comparable neutrino component. We compute the event rates for the resonant production of "right" selectrons and "right" squarks in mSUGRA, when UHE neutralinos of energy larger than 10^5 GeV scatter off electrons and quarks in an earth-based detector like IceCube. When the resonant channel dominates in the total \chi-e,\chi-q scattering cross section, the only model parameters affecting the corresponding visible signal rates turn out to be the physical masses of the resonant right-scalar and of the lightest neutralino. We compare the expected number of supersymmetric events with the rates corresponding to the expected Glashow W resonance and to the continuum UHE \nu-N scattering for realistic power-law spectra. We find that the event rate in the leptonic selectron channel is particularly promising, and can reach a few tens for a one-year exposure in IceCube. Finally, we note that UHE neutralinos at much higher energies (up to hundreds ZeV) may produce sneutrino resonances by scattering off relic neutrinos in the Local Group hot dark halo. The consequent \tilde{\nu}-burst into hadronic final states could mimic Z-burst events, although with quite smaller conversion efficiency.Comment: 23 pages, 4 figures; one reference adde

Оценка свойств костнозамещающих материалов на основе полиэтиленгликоль диакрилата и октакальциевого фосфата на модели монокортикального диафизарного дефекта бедренной кости крысы: экспериментальное исследование

Background. The problem of bone defects replacement is relevant nowadays, that is why many scientists create new synthetic bone substitutes, but the ideal material has not been found so far. The aims of the study: 1) to determine the suitability of the monocortical defect model in the rat femur diaphysis with additional prophylactic reinforcement with a bone plate for assessing the biological properties of implanted materials using the commercially available ChronOS material as an example; 2) to assess of the osteoconductive properties of composite materials based on poly(ethylene glycol)diacrylate and octacalcium phosphate with architecture Kelvin and gyroid types on the developed model. Methods. A prospective study, level of evidence II. A monocortical defect of the rat femoral diaphysis (length 7 mm) was produced under anaesthesia in aseptic conditions and fixed with a polyetheretherketone plate and six titanium screws. In the control group, the defect was left empty. In other groups, blocks of one of three materials were implanted сhronOS and composites of poly(ethylene glycol)diacrylate and octacalcium phosphate with 3D-printed Kelvin and gyroid architectures. After 3 and 6 weeks, the rats were sacrificed, and histological examination of the defect zone was performed. The amount of newly formed bone tissue was histometricly assessed, followed by statistical processing of the results. Results. All rats have reached the planned endpoint, and there were no infectious complications or loss of fixation. Histological examination of the defect zone revealed minimal bone growth in the Control group, rather slow bone formation in the Gyroid group, and statistically significantly more pronounced bone formation in the pores of the materials in the Kelvin and Chronos groups. Conclusions. Bone defect in this model was not spontaneously filled with bone tissue and allowed us to study the biological properties of bone substitutes (the ability to biodegrade and osteoconductive properties). The osteoconductive properties of a composite material based on poly(ethylene glycol)diacrylate and octacalcium phosphate with a Kelvin architecture are higher than with a gyroid architecture and are comparable to that of the сhronOS.Актуальность. Проблема замещения дефектов кости актуальна в настоящее время, постоянно ведутся поиски новых синтетических костнозамещающих материалов, однако идеальный материал не найден до сих пор. Цели исследования: 1) определение пригодности модели монокортикального дефекта диафиза бедренной кости крысы с дополнительным профилактическим армированием при помощи накостной пластины для оценки биологических свойств имплантируемых материалов на примере коммерчески доступного материала сhronOS; 2) оценка остеокондуктивных свойств композитных материалов на основе полиэтиленгликоль диакрилата и октакальциевого фосфата с архитектурой Кельвина и типа гироид на разработанной модели. Материал и методы. Монокортикальный дефект диафиза бедренной кости крыс размером 7 мм в длину производили под наркозом в асептических условиях операционной и фиксировали полиэфирэфиркетоновой пластиной и шестью титановыми винтами. Крыс распределяли случайным образом на четыре группы по 12 особей в каждой. В группе Контроль у животных костный дефект не заполняли. У животных в группе Хронос дефект заполняли подготовленным материалом chronOS в виде полуцилиндрического блока, в группе Кельвин исследуемым материалом с архитектурой Кельвина, в группе Гироид исследуемым материалом с архитектурой типа гироид. Через 3 и 6 нед. крыс выводили из эксперимента и производили гистологическое исследование зоны дефекта. Затем выполняли гистометрическую оценку количества новообразованной костной ткани с последующей статистической обработкой результатов. Результаты. В ходе эксперимента все животные достигли планируемой конечной точки, инфекционные осложнения и потеря фиксации зафиксированы не были. При гистологическом исследовании зоны дефекта выявлен минимальный рост кости в группе Контроль, достаточно медленное образование кости в материале группы Гироид и статистически значимо более выраженное образование костной ткани в порах материалов в группах Кельвин и Хронос. Заключение. Разработанная модель дефекта кости спонтанно не заполняется костной тканью и позволяет проводить изучение биологических свойств костнопластических материалов (способность к биодеградации и остеокондуктивные свойства). Остеокондуктивные свойства композитного материала на основе полиэтиленгликоль диакрилата и октакальциевого фосфата с архитектурой Кельвина выше, чем с архитектурой типа гироид, и сопоставимы с таковыми у материала сhronOS

Study of the effect of neutrino oscillations on the supernova neutrino signal in the LVD detector

The LVD detector, located in the INFN Gran Sasso National Laboratory (Italy), studies supernova neutrinos through the interactions with protons and carbon nuclei in the liquid scintillator and interactions with the iron nuclei of the support structure. We investigate the effect of neutrino oscillations in the signal expected in the LVD detector. The MSW effect has been studied in detail for neutrinos travelling through the collapsing star and the Earth. We show that the expected number of events and their energy spectrum are sensitive to the oscillation parameters, in particular to the mass hierarchy and the value of $\theta_{13}$, presently unknown. Finally we discuss the astrophysical uncertainties, showing their importance and comparing it with the effect of neutrino oscillations on the expected signal.Comment: Accepted for pubblication on Astroparticle Physics. 36 pages, 18 figure

The spectrum features of UHECRs below and surrounding GZK

The energy spectrum of UHECRs is discussed on the basis of the Yakutsk array database analysis. In the region E=0.1 to 30 EeV the showers are detected under trigger-500, while at energies above 30 EeV the whole acceptance area for trigger-1000 is used in order to utilize all the data available in the region of GZK cutoff.Comment: Invited talk at CRIS2004: GZK and surroundings, Catania, Italy, 31.05.04. To appear in Nucl. Phys. B Proc. Supp

Relic neutrino masses and the highest energy cosmic rays

We consider the possibility that a large fraction of the ultrahigh energy cosmic rays are decay products of Z bosons which were produced in the scattering of ultrahigh energy cosmic neutrinos on cosmological relic neutrinos. We compare the observed ultrahigh energy cosmic ray spectrum with the one predicted in the above Z-burst scenario and determine the required mass of the heaviest relic neutrino as well as the necessary ultrahigh energy cosmic neutrino flux via a maximum likelihood analysis. We show that the value of the neutrino mass obtained in this way is fairly robust against variations in presently unknown quantities, like the amount of neutrino clustering, the universal radio background, and the extragalactic magnetic field, within their anticipated uncertainties. Much stronger systematics arises from different possible assumptions about the diffuse background of ordinary cosmic rays from unresolved astrophysical sources. In the most plausible case that these ordinary cosmic rays are protons of extragalactic origin, one is lead to a required neutrino mass in the range 0.08 eV - 1.3 eV at the 68 % confidence level. This range narrows down considerably if a particular universal radio background is assumed, e.g. to 0.08 eV - 0.40 eV for a large one. The required flux of ultrahigh energy cosmic neutrinos near the resonant energy should be detected in the near future by AMANDA, RICE, and the Pierre Auger Observatory, otherwise the Z-burst scenario will be ruled out.Comment: 19 pages, 22 figures, REVTeX