27 research outputs found
Inference on Categorical Survey Response: A Predictive Approach
We consider the estimation of finite population proportions of categorical survey responses obtained by probability sampling. The customary design-based estimator does not make use of the auxiliary data available for all the population units at the estimation stage. We adopt a model-based predictive approach to incorporate this information and make the estimates more efficient. In the first part of our paper we consider a multinomial logit type model when logit function is a known parametric function of the covariates. We then use it for the prediction of non-sampled responses. This together with sampled responses is used to obtain the estimates of the proportions. The asymptotic biases and variances of these estimators are obtained. The main drawback of this approach is, being a parametric model it may suffer from model misspecification and thus, may lose it’s efficiencies over the usual design-based estimates. To overcome this drawback, in the next part of this paper we replace the multinomial logit type model by a nonparametric model using recently developed random coefficients splines models. Finally, we carry out a simulation study. It shows that the nonparametric approach may lead to an appreciable improvement over both parametric and design-based approaches when the regression function is quite different from multinomial logit.
Three-dimensional quasi-quantized Hall insulator phase in SrSi2
In insulators, the longitudinal resistivity becomes infinitely large at zero
temperature. For classic insulators, the Hall conductivity becomes zero at the
same time. However, there are special systems, such as two-dimensional quantum
Hall isolators, in which a more complex scenario is observed at high magnetic
fields. Here, we report experimental evidence for a quasi-quantized Hall
insulator in the quantum limit of the three-dimensional semimetal SrSi2. Our
measurements reveal a magnetic field-range, in which the longitudinal
resistivity diverges with decreasing temperature, while the Hall conductivity
approaches a quasi-quantized value that is given only by the conductance
quantum and the Fermi wave vector in the field-direction. The quasi-quantized
Hall insulator appears in a magnetic-field induced insulating ground state of
three-dimensional materials and is deeply rooted in quantum Hall physics.Comment: 29 pages including SI, 3 main figures and 6 SI figure
Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the
India-based Neutrino Observatory (INO) is designed to study the atmospheric
neutrinos and antineutrinos separately over a wide range of energies and path
lengths. The primary focus of this experiment is to explore the Earth matter
effects by observing the energy and zenith angle dependence of the atmospheric
neutrinos in the multi-GeV range. This study will be crucial to address some of
the outstanding issues in neutrino oscillation physics, including the
fundamental issue of neutrino mass hierarchy. In this document, we present the
physics potential of the detector as obtained from realistic detector
simulations. We describe the simulation framework, the neutrino interactions in
the detector, and the expected response of the detector to particles traversing
it. The ICAL detector can determine the energy and direction of the muons to a
high precision, and in addition, its sensitivity to multi-GeV hadrons increases
its physics reach substantially. Its charge identification capability, and
hence its ability to distinguish neutrinos from antineutrinos, makes it an
efficient detector for determining the neutrino mass hierarchy. In this report,
we outline the analyses carried out for the determination of neutrino mass
hierarchy and precision measurements of atmospheric neutrino mixing parameters
at ICAL, and give the expected physics reach of the detector with 10 years of
runtime. We also explore the potential of ICAL for probing new physics
scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration,
Contents identical with the version published in Pramana - J. Physic
Magnetic Properties of Transition Metal Oxides with Novel Crystal Structure
The family of transition metal oxides (TMOs) are acclaimed for their fascinating,
complex, and diverse thermodynamic properties. This complexity and diversity are
the manifestation of strong interplay between electronic, lattice, orbital and spin degrees of freedom. The magnetic ground states of such oxides depend strongly on the oxygen ions surrounding the metal and also on the interaction pathways between
two adjacent metal ions, which is often mediated through the 2p levels of oxygen.
Therefore, the magnetism of TMOs is closely connected to the crystal structure of the material concerned. The thesis entitled “Magnetic Properties of Transition Metal Oxides with Novel Crystal Structures” is devoted to the experimental investigations focusing the magnetic properties of some exotic transition metal oxides with unusual crystal structures. Where necessary, the electronic properties (dc and ac conductivity, dielectric permittivity, impedance and electric modulus analysis etc.) have also been studied to have a comprehensive understanding of the systems. All the results and analyses based on the investigations performed during this tenure have been included in this thesis along with the theoretical background and experimental methodologies.The research was carried out under the supervision of Prof. Subham Majumdar of the Solid State Physics division under SPS [School of Physical Sciences]The research was conducted under CSIR fellowshi
Wreath product of a semigroup and a Γ-semigroup
Let S = {a,b,c,...} and Γ = {α,β,γ,...} be two nonempty sets. S is called a Γ -semigroup if aαb ∈ S, for all α ∈ Γ and a,b ∈ S and (aαb)βc = aα(bβc), for all a,b,c ∈ S and for all α,β ∈ Γ. In this paper we study the semidirect product of a semigroup and a Γ-semigroup. We also introduce the notion of wreath product of a semigroup and a Γ-semigroup and investigate some interesting properties of this product