FaRe: a Mathematica package for tensor reduction of Feynman integrals

We present FaRe, a package for Mathematica that implements the decomposition of a generic tensor Feynman integral, with arbitrary loop number, into scalar integrals in higher dimension. In order for FaRe to work, the package FeynCalc is needed, so that the tensor structure of the different contributions is preserved and the obtained scalar integrals are grouped accordingly. FaRe can prove particularly useful when it is preferable to handle Feynman integrals with free Lorentz indices and tensor reduction of high-order integrals is needed. This can then be achieved with several powerful existing tools.Comment: Matches version to appear on the International Journal of Modern Physics

Supersymmetric SO(10)SO(10)-inspired leptogenesis and a new N2N_2-dominated scenario

We study the supersymmetric extension of $SO(10)$-inspired thermal leptogenesis showing the constraints on neutrino parameters and on the reheat temperature $T_{\rm RH}$ that derive from the condition of successful leptogenesis from next-to-lightest right handed (RH) neutrinos ($N_2$) decays and the more stringent ones when independence of the initial conditions (strong thermal leptogenesis) is superimposed. In the latter case, the increase of the lightest right-handed neutrino ($N_1$) decay parameters helps the wash-out of a pre-existing asymmetry and constraints relax compared to the non-supersymmetric case. We find significant changes especially in the case of large $\tan\beta$ values $(\gtrsim 15)$. In particular, for normal ordering, the atmospheric mixing angle can now be also maximal. The lightest (ordinary) neutrino mass is still constrained within the range $10 \lesssim m_1/{\rm meV} \lesssim 30$ (corresponding to $75\lesssim \sum_i m_i/{\rm meV} \lesssim 120$). Inverted ordering is still disfavoured, but an allowed region satisfying strong thermal leptogenesis opens up at large $\tan\beta$ values. We also study in detail the lower bound on $T_{\rm RH}$ finding $T_{\rm RH}\gtrsim 1 \times 10^{10}\,{\rm GeV}$ independently of the initial $N_2$ abundance. Finally, we propose a new $N_2$-dominated scenario where the $N_1$ mass is lower than the sphaleron freeze-out temperature. In this case there is no $N_1$ wash-out and we find $T_{\rm RH} \gtrsim 1\times 10^{9}\,{\rm GeV}$. These results indicate that $SO(10)$-inspired thermal leptogenesis can be made compatible with the upper bound from the gravitino problem, an important result in light of the role often played by supersymmetry in the quest of a realistic model of fermion masses.Comment: 35 pages, 10 figures; v3: matches JCAP versio

Offsets and polarization at strained AlN/GaN polar interfaces

The strain induced by lattice mismatch at the interface is responsible for the different value of the band discontinuities observed recently for the AlN/GaN (AlN on GaN) and the GaN/AlN (GaN on AlN) polar (0001) interface. We present a first-principles calculation of valence band offsets, interface dipoles, strain-induced piezoelectric fields, relaxed geometric structure, and formation energies. Our results confirm the existence of a large forward-backward asymmetry for this interface.Comment: 6 pages, 2 figures, MRS style (enclosed), to appear in MRS Proc. 44

Epidemic Threshold in Continuous-Time Evolving Networks

Current understanding of the critical outbreak condition on temporal networks relies on approximations (time scale separation, discretization) that may bias the results. We propose a theoretical framework to compute the epidemic threshold in continuous time through the infection propagator approach. We introduce the {\em weak commutation} condition allowing the interpretation of annealed networks, activity-driven networks, and time scale separation into one formalism. Our work provides a coherent connection between discrete and continuous time representations applicable to realistic scenarios.Comment: 13 pages, 2 figure

SIMULAÇÃO NUMÉRICA DO COMPORTAMENTO DINÂMICO DE PEÇAS DELGADAS NO PROCESSO DE FRESAMENTO

TCC (graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Engenharia Naval.Na engenharia naval é comum a aplicação de peças delgadas, como pás de hélices e aletas de trocadores de calor. Muitas vezes, essas peças passam por um processo de usinagem, seja este para desbaste ou acabamento superficial. Por se tratarem de componentes relativamente flexíveis, a usinagem destes componentes é um processo delicado. Em aplicações práticas relacionadas à usinagem de uma peça, a frequência de ressonância é sempre um parâmetro importante e deve ser considerado. É inerente a todo o processo de usinagem a remoção de material, portanto variações na massa da peça existem. Além disso, como se altera a geometria das peças, variações na rigidez também estão presentes. Estes dois parâmetros determinam a frequência natural de um objeto e aliados ao fator de amortecimento, determinam também a frequência de ressonância. Outro fator que influencia na rigidez do conjunto é o sistema de fixação. Deve-se evitar excitar estes componentes em frequências próximas as de ressonância. A fim de minimizar as vibrações da peça no processo de usinagem e consequentemente melhorar o acabamento superficial, o presente trabalho busca, através da simulação numérica pelo método dos elementos finitos, prever o comportamento dinâmico de determinado sistema, analisando suas vibrações. As simulações numéricas foram efetuadas com códigos próprios, tanto para o domínio do tempo quanto para o domínio da frequência, utilizando-se de elemento de viga. Correlacionando-se amplitudes de vibrações com rugosidade, foi possível estimar o acabamento superficial da peça usinada.Thin pieces are widely used during the process of marine construction and engineering, like propeller blades and fin heat exchangers. Several times, those pieces will be machined, using roughing or finishing operation. Those pieces have a low stiffness, resulting on a very sensitive and fragile process. During the machining of a component, the resonance frequency is always an important parameter, and it should be considered. In every machining process there is always material removal, consequently, the mass of the component will change along the process; also, as the geometry is changing too, the stiffness of the workpiece will not be constant as well. The fixturing system will also change the stiffness of the system. The natural frequency of a component is a function of both mass and stiffness, so this frequency will change too, the resonance frequency will also switch, once it is a function of those both parameters and the damping ratio. The condition where the excitation frequency is close to the resonance frequency must be avoided, because of the workpiece will oscillate with high vibration amplitudes, those may be catastrophic, they can cause a bad surface finish, or they can even cause failures in both machine and tool. The main goal is to predict the dynamic behavior of the workpiece during the milling process. As an important tool, the numeric simulation will be applied. All simulations used were developed by the authors, and both time and frequency domain are applied, using beam elements. The vibration amplitudes can be directly correlated to the roughness and surface finish quality, making it possible to predict the finished workpiece surface quality

New Signatures of the Milky Way Formation in the Local Halo and Inner Halo Streamers in the Era of Gaia

We explore the vicinity of the Milky Way through the use of spectro-photometric data from the Sloan Digital Sky Survey and high-quality proper motions derived from multi-epoch positions extracted from the Guide Star Catalogue II database. In order to identify and characterise streams as relics of the Milky Way formation, we start with classifying, select, and study $2417$ subdwarfs with $\rm{[Fe/H] < -1.5}$ up to $3$ kpc away from the Sun as tracers of the local halo system. Then, through phase-space analysis, we find statistical evidence of five discrete kinematic overdensities among $67$ of the fastest-moving stars, and compare them to high-resolution N-body simulations of the interaction between a Milky-Way like galaxy and orbiting dwarf galaxies with four representative cases of merging histories. The observed overdensities can be interpreted as fossil substructures consisting of streamers torn from their progenitors, such progenitors appear to be satellites on prograde and retrograde orbits on different inclinations. In particular, of the five detected overdensities, two appear to be associated, yelding twenty-one additional main-sequence members, with the stream of Helmi et al. (1999) that our analysis confirms on a high inclination prograde orbit. The three newly identified kinematic groups could be associated with the retrograde streams detected by Dinescu (2002) and Kepley et al. (2007), whatever their origin, the progenitor(s) would be on retrograde orbit(s) and inclination(s) within the range $10^{\circ} \div 60^{\circ}$. Finally, we use our simulations to investigate the impact of observational errors and compare the current picture to the promising prospect of highly improved data expected from the Gaia mission.Comment: 16 pages, 10 figures, 6 Tables. Accepted for publication in The Astronomical Journa

Neutrino parameters and the N2N_2-dominated scenario of leptogenesis

We briefly review the main aspects of leptogenesis, describing both the unflavoured and the flavoured versions of the $N_2$-dominated scenario. A study of the success rates of both classes of models has been carried out. We comment on these results and discuss corrective effects to this simplest scenario. Focusing on the flavoured case, we consider the conditions required by strong thermal leptogenesis, where the final asymmetry is fully independent of the initial conditions. Barring strong cancellations in the seesaw formula and in the flavoured decay parameters, we show that strong thermal leptogenesis favours a lightest neutrino mass m_1\gtrsim10\,\mbox{meV} for normal ordering (NO) and m_1\gtrsim 3\,\mbox{meV} for inverted ordering (IO). Finally, we briefly comment on the power of absolute neutrino mass scale experiments to either support or severely corner strong thermal leptogenesis.Comment: Contribution to the Proceedings of the NuPhys2013 Conference: Prospects in Neutrino Physics, 19-20 December 2013, IOP, Londo

A consistent model for leptogenesis, dark matter and the IceCube signal

We discuss a left-right symmetric extension of the Standard Model in which the three additional right-handed neutrinos play a central role in explaining the baryon asymmetry of the Universe, the dark matter abundance and the ultra energetic signal detected by the IceCube experiment. The energy spectrum and neutrino flux measured by IceCube are ascribed to the decays of the lightest right-handed neutrino $N_1$, thus fixing its mass and lifetime, while the production of $N_1$ in the primordial thermal bath occurs via a freeze-in mechanism driven by the additional $SU(2)_R$ interactions. The constraints imposed by IceCube and the dark matter abundance allow nonetheless the heavier right-handed neutrinos to realize a standard type-I seesaw leptogenesis, with the $B-L$ asymmetry dominantly produced by the next-to-lightest neutrino $N_2$. Further consequences and predictions of the model are that: the $N_1$ production implies a specific power-law relation between the reheating temperature of the Universe and the vacuum expectation value of the $SU(2)_R$ triplet; leptogenesis imposes a lower bound on the reheating temperature of the Universe at 7\times10^9\,\mbox{GeV}. Additionally, the model requires a vanishing absolute neutrino mass scale $m_1\simeq0$.Comment: 19 pages, 4 figures. Constraints from cosmic-ray antiprotons and gamma rays added, with hadrophobic assignment of the matter multiplets to satisfy bounds. References added. Matches version published in JHE

Zooplankton - indicator of ecological status in Mediterranean ponds

Mediteranske lokve su plitka vodena tijela koja često presušuju. U prošlosti su bile bitan izvor vode, a danas su izložene različitim negativnim antropogenim utjecajima. Zooplanktonski organizmi značajno pridonose bioraznolikosti lokvi, a ujedno su relevantni pokazatelji ekološkog stanja. Ciljevi ovog rada bili su utvrditi: (i) brojnosti i raznolikost zooplanktona te dominantne vrste i njihovu ekološku ulogu; (ii) utjecaj okolišnih čimbenika i predacije na sastav zooplanktona te (iii) povezanost funkcionalnih obilježja zooplanktona i ekološkog stanja kao osnova prijedloga mjera upravljanja i očuvanja jadranskih lokvi. U deset lokvi determinirano je 57 zooplanktonskih vrsta, a kolnjaci su dominirali sa 40 vrsta. Rezultati ukazuju da je na sastav zooplanktona značajno utjecala kompleksnost habitusa makrofita te ribe kao vizualni predatori. Zooplankton lokvi sa sumberznim makrofitima, bez riba, obilježavala je veća brojnost i raznolikost, te vrlo dobro ekološko stanje s većim udjelom planktonskih rakova. U lokvama dobrog ekološkog stanja s dominacijom kolnjaka, bile su prisutne ribe te pokrovnost emerznim i flotantnim makrofitima. Mala brojnost i raznolikost zooplanktona obilježavala je lokve umjereno promijenjenog ekološkog stanja s malom pokrovnošću makrofitima. Antropogeni utjecaji na mediteranske lokve iziskuju sustavno upravljanje i očuvanje lokvi kako bi se umanjili negativni utjecaji i obnovile njihove ekološke funkcije te očuvala bioraznolikost.Mediterranean ponds are shallow water bodies and often temporary. In the past, they were important sources of water, and recently are exposed to various negative anthropogenic impacts. Zooplankton organisms contribute significantly to pond biodiversity and are relevant indicators of ecological status. The objectives of this study were to establish: (i) the abundance and diversity of zooplankton and the ecological role of dominant species; (ii) the influence of environmental factors and predation on zooplankton composition; and (iii) the correlation of zooplankton functional traits and ecological status as basis for the proposal of management and conservation of Adriatic ponds. Among 57 zooplankton species, rotifers dominated with 40 species. The results indicate the zooplankton composition was significantly influenced by complexity of the macrophytes and fish predation. Zooplankton in ponds with submerged macrophytes, without fish, were characterized by high abundance and diversity in very good ecological status and higher ratio of planktonic crustaceans. In ponds of good ecological status with dominance of rotifers, fish were present, and coverage of emergent and flotant macrophytes. The low abundance and diversity of zooplankton marked ponds of moderately altered ecological status with scarce macrophyte coverage. Anthropogenic impacts on Mediterranean ponds require systematic management and conservation to minimize adverse impacts and restore their ecological functions and preserve biodiversity