4,928 research outputs found
Solving the strong CP problem with non-conventional CP
A very simple model is presented where all CP violation in Nature is
spontaneous in origin. The CKM phase is generated unsuppressed and the strong
CP problem is solved with only moderately small couplings between the SM and
the CP violation sector or mediator sector because corrections to
arise only at two loops. The latter feature follows from an
underlying unconventional CP symmetry of order 4 imposed in the sectors beyond
the SM composed of only two vector-like quarks of charge and one complex
scalar singlet. No additional symmetry is necessary to implement the
Nelson-Barr mechanism.Comment: Comments added, comply with published versio
An Model for Lepton Mass Matrices with Nearly Minimal Texture
We propose a simple extension of the electroweak standard model based on the
discrete symmetry that is capable of realizing a nearly minimal
Fritzsch-type texture for the Dirac mass matrices of both charged leptons and
neutrinos. This is achieved with the aid of additional and
symmetries, one of which can be embedded in . Five complex scalar
singlet fields are introduced in addition to the SM with right-handed
neutrinos. Although more general, the modified texture of the model retains the
successful features of the minimal texture without fine-tuning; namely, it
accommodates the masses and mixing of the leptonic sector and relates the
emergence of large leptonic mixing angles with the seesaw mechanism. For large
deviations of the minimal texture, both quasidegenerate spectrum or inverted
hierarchy are allowed for neutrino masses.Comment: 11pp, 2 figures. v2: vev alignment addressed, additional analysis
performed; to appear in PR
The Quest for an Intermediate-Scale Accidental Axion and Further ALPs
The recent detection of the cosmic microwave background polarimeter
experiment BICEP2 of tensor fluctuations in the B-mode power spectrum basically
excludes all plausible axion models where its decay constant is above
GeV. Moreover, there are strong theoretical, astrophysical, and cosmological
motivations for models involving, in addition to the axion, also axion-like
particles (ALPs), with decay constants in the intermediate scale range, between
GeV and GeV. Here, we present a general analysis of models
with an axion and further ALPs and derive bounds on the relative size of the
axion and ALP photon (and electron) coupling. We discuss what we can learn from
measurements of the axion and ALP photon couplings about the fundamental
parameters of the underlying ultraviolet completion of the theory. For the
latter we consider extensions of the Standard Model in which the axion and the
ALP(s) appear as pseudo Nambu-Goldstone bosons from the breaking of global
chiral (Peccei-Quinn (PQ)) symmetries, occuring accidentally as low
energy remnants from exact discrete symmetries. In such models, the axion and
the further ALP are protected from disastrous explicit symmetry breaking
effects due to Planck-scale suppressed operators. The scenarios considered
exploit heavy right handed neutrinos getting their mass via PQ symmetry
breaking and thus explain the small mass of the active neutrinos via a seesaw
relation between the electroweak and an intermediate PQ symmetry breaking
scale. We show some models that can accommodate simultaneously an axion dark
matter candidate, an ALP explaining the anomalous transparency of the universe
for -rays, and an ALP explaining the recently reported 3.55 keV gamma
line from galaxies and clusters of galaxies, if the respective decay constants
are of intermediate scale.Comment: 43pp, 4 figures. v2: version accepted for publication in JHE
Structure of potentials with Higgs doublets
Extensions of the Standard Model with Higgs doublets are simple
extensions presenting a rich mathematical structure. An underlying Minkowski
structure emerges from the study of both variable space and parameter space.
The former can be completely parametrized in terms of two future lightlike
Minkowski vectors with spatial parts forming an angle whose cosine is
. For the parameter space, the Minkowski parametrization enables
one to impose sufficient conditions for bounded below potentials, characterize
certain classes of local minima and distinguish charge breaking vacua from
neutral vacua. A particular class of neutral minima presents a degenerate mass
spectrum for the physical charged Higgs bosons.Comment: 11 pages. Revtex4. Typos corrected. Few comments adde
ASSESSING THE QUALITY OF SOFTWARE DEVELOPMENT TUTORIALS AVAILABLE ON THE WEB
Both expert and novice software developers frequently access software development resources available on the Web in order to lookup or learn new APIs, tools and techniques. Software quality is affected negatively when developers fail to find high-quality information relevant to their problem. While there is a substantial amount of freely available resources that can be accessed online, some of the available resources contain information that suffers from error proneness, copyright infringement, security concerns, and incompatible versions. Use of such toxic information can have a strong negative effect on developer’s efficacy. This dissertation focuses specifically on software tutorials, aiming to automatically evaluate the quality of such documents available on the Web. In order to achieve this goal, we present two contributions: 1) scalable detection of duplicated code snippets; 2) automatic identification of valid version ranges.
Software tutorials consist of a combination of source code snippets and natural language text. The code snippets in a tutorial can originate from different sources, perhaps carrying stringent licensing requirements or known security vulnerabilities. Developers, typically unaware of this, can reuse these code snippets in their project. First, in this thesis, we present our work on a Web-scale code clone search technique that is able to detect duplicate code snippets between large scale document and source code corpora in order to trace toxic code snippets.
As software libraries and APIs evolve over time, existing software development tutorials can become outdated. It is difficult for software developers and especially novices to determine the expected version of the software implicit in a specific tutorial in order to decide whether the tutorial is applicable to their software development environment. To overcome this challenge, in this thesis we present a novel technique for automatic identification of the valid version range of software development tutorials on the Web
Altitude variations of cosmic-ray soft and hard components observed by airborne detectors
The altitude variations of cosmic-ray total and hard components were measured up to 12,000 m on board a jet liner over Japan island on December, 1981. Observed results together with soft component are presented comparing with the model calculations through the atmosphere by applying the hadronic cascade
Axion Like Particles and the Inverse Seesaw Mechanism
Light pseudoscalars known as axion like particles (ALPs) may be behind
physical phenomena like the Universe transparency to ultra-energetic photons,
the soft -ray excess from the Coma cluster, and the 3.5 keV line. We
explore the connection of these particles with the inverse seesaw (ISS)
mechanism for neutrino mass generation. We propose a very restrictive setting
where the scalar field hosting the ALP is also responsible for generating the
ISS mass scales through its vacuum expectation value on gravity induced
nonrenormalizable operators. A discrete gauge symmetry protects the theory from
the appearance of overly strong gravitational effects and discrete anomaly
cancellation imposes strong constraints on the order of the group. The
anomalous U symmetry leading to the ALP is an extended lepton number and
the protective discrete symmetry can be always chosen as a subgroup of a
combination of the lepton number and the baryon number.Comment: 29pp. v4: published version with erratum. Conclusions unchange
Preparation and in vitro evaluation of primaquine-conjugated gum arabic microspheres
Gum arabic, a branched polysaccharide, was oxidized using periodate to generate reactive aldehyde groups on the biopolymer. Primaquine, an 8-aminoquinoline, was covalently coupled onto oxidized gum arabic via an imine bond and simultaneously fabricated into microspheres of less than 2 μm in size by heat denaturation in a reverse emulsion of 1:1 light paraffin oil and toluene stabilized by sorbitan sesquioleate as the surfactant. The covalent binding of primaquine to the polysaccharide using the clinically used water-soluble form of the drug primaquine phosphate was achieved in the presence of borate buffer of pH 11. Up to 35% of the drug could be bound to the polymer backbone depending on the concentration of the drug employed initially and the degree of oxidation of the polysaccharide. Interestingly, both the aliphatic and the hindered aromatic amino groups of primaquine were found to react with the aldehyde functions through Schiff base formation leading to cross-linking of the polysaccharide with the drug itself. In vitro release of the drug from microspheres into phosphate buffered saline (PBS, pH 7.4, 0.1 M) at 37 °C showed that the release of primaquine from the matrix was slow, although gradually increased with time. The maximum released was below 50% of the drug payload even after 10 days. Release into simulated gastric and intestinal fluids was faster compared to the release in PBS due to rapid hydrolysis of the Schiff's linkage in the gastric fluid. A possible reason for the poor hydrolytic susceptibility of the Schiff's linkage is suggested based on the unequal reactivity of the amino groups on primaquine and its relevance in possible therapeutic application of this polymer-drug conjugate discussed
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