6,447 research outputs found
A study on a minimally broken residual TBM-Klein symmetry with its implications on flavoured leptogenesis and ultra high energy neutrino flux ratios.
No full textWe present a systematic study on minimally perturbed neutrino mass matrices which at the leading order give rise to Tri-BiMaximal (TBM) mixing due to a residual Bbb Z2× Bbb Z2μτ Klein symmetry in the neutrino mass term of the low energy effective seesaw Lagrangian. Considering only the breaking of Bbb Z2μτ with two relevant breaking parameters (epsilon4,6'), after a comprehensive numerical analysis, we show that the phenomenologically viable case in this scenario is a special case of TM1 mixing. For this class of models, from the phenomenological perspective, one always needs large breaking (more than 45%) in one of the breaking parameters. However, to be consistent the maximal mixing of θ23, while more than 35% breaking is needed in the other, a range 49.4o−53o and 38o−40o could be probed allowing breaking up to 25% in the same parameter. Thus though this model cannot distinguish the octant of θ23, non-maximal mixing is preferred from the viewpoint of small breaking. The full Bbb Z2× Bbb Z2μτ symmetry leads to a degeneracy in the eigenvalues of right handed (RH) neutrino mass matrices (MR). Nevertheless, breaking of Bbb Z2μτ which is also necessary to generate nonzero θ13 in this model, lifts that degeneracy. Thus unlike the standard N1-leptogenesis scenario where only the decays and other interactions due to the lightest RH neutrino N1 are relevant, here all the RH neutrinos contribute to the process of baryogenesis via leptogenesis due to the small mass splitting controlled by the Bbb Z2μτ breaking parameters. Including flavour coupling effects (In general, which have been partially included in all the leptogenesis studies in perturbed TBM framework), we solve flavour dependent coupled Boltzmann equations for heavy neutrino as well as the light leptonic number densities to compute the final baryon asymmetry YB. Thus our analysis and results pertaining to a successful leptogenesis are more accurate than any other studies in existing literature that deal with perturbed TBM scenario. Finally, in the context of recent discovery of the ultra high energy (UHE) neutrino events at IceCube, assuming UHE neutrinos originate from purely astrophysical sources, we obtain prediction on the neutrino flux ratios at neutrino telescopes
Representing seesaw neutrino models and their motion in lepton flavour space
No full textWe discuss how seesaw neutrino models can be graphically represented in lepton flavour space. We examine various popular models and show how this representation helps understanding their properties and connection with experimental data showing in particular how certain texture zero models are ruled out. We also introduce a new matrix, the bridging matrix, that brings from the light to the heavy neutrino mass flavour basis, showing how this is related to the orthogonal matrix and how different quantities are easily expressed through it. We then show how one can randomly generate orthogonal and leptonic mixing matrices uniformly covering all flavour space in an unbiased way (Haar-distributed matrices). Using the isomorphism between the group of complex rotations and the Lorentz group, we also introduce the concept of Lorentz boost in flavour space for a seesaw model and how this has an insightful physical interpretation. Finally, as a significant application, we consider N2-leptogenesis. Using current experimental values of low energy neutrino parameters, we show that the probability that at least one flavoured decay parameter of the lightest right-handed neutrino is smaller than unity is about 49% (to be compared with the tiny probability that the total decay parameter is smaller than unity, P (KI< 1) ∼ 0.1%, confirming the crucial role played by flavour effects). On the other hand when m1 ≳ 0.1 eV this probability reduces to less than 5%, showing how also N2-leptogenesis disfavours degenerate light neutrinos
Non-thermal production of lepton asymmetry and dark matter in minimal seesaw with right handed neutrino induced Higgs potential
No full textWithin Type-I seesaw mechanism, Higgs mass can be dynamically generated via quantum effects of the right handed neutrinos assuming the potential is nearly conformal at the Ultra-Violet. The scenario, named as the "Neutrino Option" allows RH neutrino mass scale upto GeV to be consistent with light neutrino masses, mixing and Higgs mass. Therefore, it is not consistent with standard hierarchical thermal leptogenesis. Parameter space for thermal resonant leptogenesis is highly constrained in this model. We point out that non-thermal pair production of RH neutrinos from inflaton decay corresponds in general to a mild degree of resonance in the CP asymmetry parameter and allows RH mass scale to be smaller more than by an order of magnitude than the thermal strong resonance case. Within the similar parameter space of thermal leptogenesis, RH neutrinos can also be produced from inflaton decay along with a Dark Matter having mass 320 MeV. The main constraint in the latter scenario comes from the Ly constraints on Dark Matter free streaming. We show in addition, that the Neutrino Option introduces a 'phantom window' for the RH mass scale, in which contrary to the usual scenarios, CP asymmetry parameter for leptogenesis decreases with the increase of the RH mass scale and minimally fine-tuned seesaw models naturally exhibit this `phantom window'
Density matrix calculation of the dark matter abundance in the Higgs induced right-handed neutrino mixing model
No full textWe present new results on the calculation of the dark matter relic abundance within the Higgs induced right-handed neutrino mixing model, solving the associated density matrix equation. For a benchmark value of the dark matter mass MDM = 220 TeV, we show the evolution of the abundance and how this depends on reheat temperature, dark matter lifetime and source right-handed neutrino mass MS, with the assumption MS < MDM. We compare the results with those obtained within the Landau-Zener approximation, showing that the latter largely overestimates the final abundance giving some analytical insight. However, we also notice that since in the density matrix formalism the production is non-resonant, this allows source right-handed neutrino masses below the W boson mass, making dark matter more stable at large mass values. This opens an allowed region for initial vanishing source right-handed neutrino abundance. For example, for MS ≳ 1 GeV, we find MDM≳ 20 PeV. Otherwise, for MS > MW∼ 100 GeV, one has to assume a thermalisation of the source right-handed neutrinos prior to the freeze-in of the dark matter abundance. This results into a large allowed range for MDM, depending on MS. For example, imposing MS ≳ 300 GeV, allowing also successful leptogenesis, we find 00.5 ≲ MDM/TeV ≲ 50. We also discuss in detail leptogenesis with two quasi-degenerate right-handed neutrinos, showing a case when observed dark matter abundance and matter-antimatter asymmetry are simultaneously reproduced. Finally, we comment on how an initial thermal source right-handed neutrino abundance can be justified and on how our results suggest that also the interesting case where MDM < MS, embeddable in usual high scale two right-handed neutrino seesaw models, might be viable
Continuing Rome
No full textRome is a city that has always been described as an eternal city. This eternal character can be found through the many traces that Rome contains of former states within its physical environment. When researching these traces, an interesting conclusion can be drawn; almost all physical elements have either fallen into decay or have continuously moved with the city to meet the needs of new social structures. But nowadays with the declaration of the city centre of Rome as one large monument, this is no longer possible. While at the same time the current social structure is crumbling. This is particularly visible with all of the Roman churches. Christianity is losing relevance fast and these church become nothing but museumpieces in the city that are no longer contributing to the current social structure of Rome. That is why this thesis proposes a radical move; to provide space in the city center for new architectural experiments by moving 10 of the 400 churches to a new location outside the city center. With the collection of 10 churches also a grand experiment will be conducted, creating a gigantic second hand religious market, using the historical logistical character of the new location. Continuing Rome is about giving the city the impulse to restart the layering that makes Rome great and to give Rome back to its own citizens for a new eternity.Architecture, Urbanism and Building Sciences | Public Buildin
Writing Rome: textual approaches to the city
No full textBook synopsis: The city of Rome is built not only of bricks and marble but also of the words of its writers. For the ancient inhabitant or visitor, the buildings of Rome, the public spaces of the city, were crowded with meanings and associations. These meanings were generated partly through activities associated with particular places, but Rome also took on meanings from literature written about the city: stories of its foundation, praise of its splendid buildings, laments composed by those obliged to leave it. Ancient writers made use of the city to explore the complexities of Roman history, power and identity. This book aims to chart selected aspects of Rome's resonance in literature and the literary resonance of Rome. A wide range of texts are explored, from later periods as well as from antiquity, since, as the author hopes to show, Gibbon, Goethe and others can be revealing guides to the literary topography of ancient Rome
A common law cocoon: Australia and the Rome II Regulation
No full textThe author considers common themes and distinctions between the new European choice of law rules for tort and delict (as found in the Rome II Regulation) and the Australian choice of law rules dealing with torts. He also discusses the extent to which European ideas about choice of law for foreign wrongs might influence reform of the law in Australia
Probing relic neutrino decays with 21 cm cosmology
No full textWe show how 21 cm cosmology can test relic neutrino radiative decays into sterile neutrinos. Using recent EDGES results, we derive constraints on the lifetime of the decaying neutrinos. If the EDGES anomaly will be confirmed, then there are two solutions, one for much longer and one for much shorter lifetimes than the age of the universe, showing how relic neutrino radiative decays can explain the anomaly in a simple way. We also show how to combine EDGES results with those from radio background observations, showing that potentially the ARCADE 2 excess can be also reproduced together with the EDGES anomaly within the proposed non-standard cosmological scenario. Our calculation of the specific intensity at the redshifts probed by EDGES can be also applied to the case of decaying dark matter
Probing maximal zero textures with broken cyclic symmetry in inverse seesaw
No full textAbstractWithin the framework of inverse seesaw mechanism we investigate neutrino mass matrices invariant under cyclic symmetry (Z3) with maximal zero texture (6 zero textures). We explore two different approaches to obtain the cyclic symmetry invariant form of the constituent matrices. In the first one we consider explicit cyclic symmetry in the neutrino sector of the Lagrangian which dictates the emerged effective neutrino mass matrix (mν) to be symmetry invariant and hence leads to a degeneracy in masses. We then consider explicit breaking of the symmetry through a dimensionless parameter ϵ′ to remove the degeneracy. It is seen that the method doesn't support the current neutrino oscillation global fit data even after considering the correction from cyclic symmetry invariant charged lepton mass matrix (ml) unless the breaking parameter is too large. In the second method, we assume the same forms of the neutrino mass matrices, however, symmetry is broken in the charged lepton sector. All the structures of the mass matrices are now dictated by an effective residual symmetry of some larger symmetry group in the Lagrangian. For illustration, we exemplify a toy model based on softly broken A4 symmetry group which leads to one of the combinations of ml, mD, MRS and μ to generate effective mν. All the emerged mass matrices predict a constraint range of the CP violating phases and atmospheric mixing angle along with an inverted hierarchical structure of the neutrino masses. Further, significant predictions on ββ0ν decay parameter |m11| and the sum of the three light neutrino masses (Σimi) are also obtained
The impact of the populace on government of the city of Rome in the fourth century A.D
No full textThe purpose of this study is to show how popular rioting and fear of popular rioting and unrest came to be such a major concern of the Prefect of the City and his subordinates during the fourth century, a period when Emperors no longer lived at Rome (and so did net have to fear for their personal safety, when Plebeians were rioting in Rome), and in the early years of which the Praetorian Guard, the only force in Rome capable of crushing popular riots by brute force, was disbanded. The first chapter deals with the status of Rome in the fourth century. It was no longer the political centre of the Empire, but it seems to have been the centre of patriotic feeling more than ever before, which is perhaps why Emperors were less harsh to the plebeians when they rioted than to provincials, and is why they took pains to help the Prefect of the City in dealing with plebeian grievances. Chapter 2 deals with the discomforts of living in Rome, and subsisting there on the one hand, and the compensations, the bread and circuses, on the other. The third chapter deals with the causes of disturbances at Rome, and how typical of the metropolises of the Empire (Rome, Alexandria, Antioch, Carthage and Constantinople) were the causes of riots, and their level of violence. Fourth century Rome is also compared to Rome in the Severan period to see how much or little it had changed. Chapter 4 concerns the short term solutions to disturbances that is the immediate options available to and adopted by the authorities once the disturbance had started. Chapter 5 deals with the laws passed by Emperors to ensure that the people got their bread and circuses, and with other areas in which Emperors concerned themselves, such as the provision of a rudimentary health service
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