136 research outputs found
Higgs vacuum stability and inflationary dynamics after BICEP2 and PLANCK dust polarisation data
If the recent detection of mode polarization of the Cosmic Microwave
Background by BICEP2 observations, withstand the test of time after the release
of recent PLANCK dust polarisation data, then it would surprisingly put the
inflationary scale near Grand Unification scale if one considers single-field
inflationary models. On the other hand, Large Hadron Collider has observed the
elusive Higgs particle whose presently observed mass can lead to electroweak
vacuum instability at high scale GeV). In this
article, we seek for a simple particle physics model which can simultaneously
keep the vacuum of the theory stable and yield high-scale inflation
successfully. To serve our purpose, we extend the Standard Model of particle
physics with a gauged symmetry which spontaneously breaks down
just above the inflationary scale. Such a scenario provides a constrained
parameter space where both the issues of vacuum stability and high-scale
inflation can be successfully accommodated. The threshold effect on the Higgs
quartic coupling due to the presence of the heavy inflaton field plays an
important role in keeping the electroweak vacuum stable. Furthermore, this
scenario is also capable of reheating the universe at the end of inflation.
Though the issues of Dark Matter and Dark Energy, which dominate the late-time
evolution of our universe, cannot be addressed within this framework, this
model successfully describes the early universe dynamics according to the Big
Bang model.Comment: Title and text are modified to match the accepted version in JCAP. 22
pages, 3 figures, Latex fil
Classifying standard model extensions effectively with precision observables
Effective theories are well established theoretical frameworks to describe the effect of energetically widely separated UV models on observables at lower energy scales. Due to the complexity of the effective theory when taking all the Standard Model symmetries and degrees of freedom into account, tensioning the entire system in a completely agnostic way against experimental measurements results in constraints on the Wilson coefficients of the effective operators that either bears little information or challenge intrinsic assumptions imposed on the effective field theory framework. In general, a specific high-scale extension of the Standard Model only induces a subset of all possible operators. Thus, by investigating which operators are induced by different classes of the Standard Model extensions and comparing to which precision observables they contribute, we show that it is possible to obtain an improved understanding of which UV model is realised in nature. We present the tree + 1 -loop matching results for dimension-6 operators of 15 different BSM scenarios onto SMEFT, and also including, the specific model-based contributions to the observables. We argue that more observables and matching with higher theoretical precision will pave the way to distinguish the single scalar extensions of the SM signatures uniquely. We promote this approach to study new sets of observables in the context of current and near future experiments
CoDEx: Wilson coefficient calculator connecting SMEFT to UV theory
CoDEx is a Mathematica package that calculates the Wilson Coefficients (WCs)
corresponding to effective operators up to mass dimension-6. Once the part of
the Lagrangian involving single as well as multiple degenerate heavy fields,
belonging to some Beyond Standard Model (BSM) theory, is given, the package can
then integrate out propagators from the tree as well as 1-loop diagrams of that
BSM theory. It then computes the associated WCs up to 1-loop level, for two
different bases: "Warsaw" and "SILH". CoDEx requires only very basic
information about the heavy field(s), e.g., Colour, Isospin, Hyper-charge,
Mass, and Spin. The package first calculates the WCs at the high scale (mass of
the heavy field(s)). We then have an option to perform the renormalisation
group evolutions (RGEs) of these operators in "Warsaw" basis, a complete one
(unlike "SILH"), using the anomalous dimension matrix. Thus, one can get all
effective operators at the electro-weak scale, generated from any such BSM
theory, containing heavy fields of spin: 0, 1/2, and 1. We have provided many
example models (both here and in the package-documentation) that more or less
encompass different choices of heavy fields and interactions. Relying on the
status of the present day precision data, we restrict ourselves up to
dimension-6 effective operators. This will be generalised for any dimensional
operators in a later version. Site: https://effexteam.github.io/CoDExComment: 25 pages, 1 figure, corrections and citations adde
Analyzing the antimicrobial efficacy of the economically important tree Knema linifolia (Roxb.) Warb
Knema linifolia is widely used for fuel wood, fodder and healthcare purposes. This plant treats various diseases in different parts of India, including Assam, Meghalaya, Alipurduar and Darjeeling districts of West Bengal. This study was carried out to determine the bactericidal properties of various parts of K. linifolia aqueous extract. The aqueous extract of the leaves, bark, stem and plant sap were tested against Escherichia coli (gram-negative bacteria) & Staphylococcus aureus (gram-positive bacteria). Among the tested extracts, both the leaf and bark extracts were found to have high bactericidal potential and can kill more than 60% of both bacterial strains with a concentration of 300µg/mL through an agar diffusion test. The MIC (Minimum Inhibitory Concentration) values for the leaf and bark extracts were recorded at ≤1000µg/mL & ≤500µg/mL, respectively. It has also been found that both the bark and leaf extracts contain high tannins, which might be essential for the antibacterial properties of Knema sp. There is currently a lack of proper documentation on using K. linifolia, which makes it challenging to conduct clinical or commercial research to support new uses in modern phototherapy. This study aims to fill this gap and provide significant information that could lead to changes in modern medicine
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