High-z Supernova Type Ia Data: non-Gaussianity and Direction Dependence

We use the $\Delta_{\chi^2}$ statistic introduced in \cite{gup08,gup10} to study directional dependence, in the high-z supernovae data. This dependence could arise due to departures from the cosmological principle or from direction dependent statistical systematics in the data. We apply our statistic to the gold data set from \cite{rie04} and \cite{rie07}, and Union2 catalogue from \cite{aman10}. Our results show that all the three data sets show a weak but consistent direction dependence. In 2007 data errors are Gaussian, however other two data sets show non-Gaussian features.Comment: 5 pages, 5 figures, 2 tables; submitted to MNRAS. arXiv admin note: substantial text overlap with arXiv:1005.286

Non-Gaussianity and direction dependent systematics in HST key project data

Two new statistics, namely $\Delta_\chi^2$ and $\Delta_\chi$, based on extreme value theory, were derived in \cite{gupta08,gupta10}. We use these statistics to study direction dependence in the HST key project data which provides the most precise measurement of the Hubble constant. We also study the non-Gaussianity in this data set using these statistics. Our results for $\Delta_\chi^2$ show that the significance of direction dependent systematics is restricted to well below one $\sigma$ confidence limit, however, presence of non-Gaussian features is subtle. On the other hand $\Delta_\chi$ statistic, which is more sensitive to direction dependence, shows direction dependence systematics to be at slightly higher confidence level, and the presence of non-Gaussian features at a level similar to the $\Delta_\chi^2$ statistic.Comment: 6 pages, 4 figures; accepted for publication in MNRA

Resource Allocation Policy for Virtualized Network Interfaces

Over the last decade, virtualization has gained widespread importance. Virtual Machines (VMs) can now share network access in hardware, or in software or in a hybridized way. Input/Output (IO) virtualization technologies based on software utilize emulation technique, but this requires Virtualization Manager which presents central processing overhead in a significant amount. Besides, each IO operation in turn poses overhead additionally and any supported advanced capabilities inherent of physical hardware are not utilized properly. Some direct assignment based IO virtualization technologies suffer from limitations to scalability. The support for Quality of Service (QoS) may be offered within the software layers at the Virtualization Manager or Guest Operating System level which interact with the IO device that is being shared. With a preliminary investigation of the functionality of the RiceNIC (an open standard platform meant for research and education into concurrent network interface design), a study of the various network interface technologies supporting IO device virtualization was carried out to precisely understand IO virtualized network interfaces. The project describes a resource allocation policy for the on-device memory of the IO device being shared, taking the instance of a complex IO device, i.e., a Network Interface Controller(NIC) supporting a reconfigurable virtualized network interface architecture design which endures multiple reconfigurable virtualized network interfaces working independently using a reconfigurable partitioned memory. It enhances the scalability of the IO device

Cosmology with decaying tachyon matter

We investigate the case of a homogeneous tachyon field coupled to gravity in a spatially flat Friedman-Robertson-Walker spacetime. Assuming the field evolution to be exponentially decaying with time we solve the field equations and show that, under certain conditions, the scale factor represents an accelerating universe, following a phase of decelerated expansion. We make use of a model of dark energy (with p=-\rho) and dark matter (p=0) where a single scalar field (tachyon) governs the dynamics of both the dark components. We show that this model fits the current supernova data as well as the canonical \LambdaCDM model. We give the bounds on the parameters allowed by the current data.Comment: 14 pages, 6 figures, v2, Discussions and references addede

Investigating the Evolution of Amati Parameters with Redshift

Gamma Ray Bursts (GRB) are among the brightest objects in the Universe and hence can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of GRBs can be used to estimate the cosmological parameters. However, the possibility of the evolution of GRBs with the redshift is a long-standing puzzle. In this work, we used 162 long-duration GRBs to determine whether GRBs below and above a certain redshift have different properties. The GRBs are split into two groups, and we fit the Amati relation for each group separately. Our findings demonstrate that estimations of the Amati parameters for the two groups are substantially dissimilar. We perform simulations to investigate whether the selection effects could cause the difference. Our analysis shows that the differences may be intrinsic, and the selection effects are not their true origin.Comment: 6 pages, 8 figure

Investigating the Hubble Tension: Effect of Cepheid Calibration

Recent observations of Type Ia supernovae (SNe) by SH0ES collaboration (R11 and R16) diverge from the value reported by recent CMBR observations utilising the Planck satellite and application of the $\Lambda CDM$ cosmological model by at least $3 \sigma$. It is among the most challenging problems in contemporary cosmology and is known as the Hubble tension. The SNe Ia in R11 and R16 were calibrated through cepheid variables in three distinct galaxies: Milky Way, LMC, and NGC4258. Carnegie Hubble Program (CHP) observations of type Ia SNe calibrated using the tip of the red giant approach yielded a somewhat different estimate for the Hubble constant. This decreased the Hubble tension from over 3$\sigma$ to below 2$\sigma$. It is a legitimate question to answer whether there are any issues with SNe Ia calibration and to investigate whether the Hubble tension is real or not. We use statistical techniques namely, ANOVA, K-S test, and t-test to examine whether the cepheid calibration is host-dependent. Our analysis shows that (i) both R11 and R16 data suffer from non-Gaussian systematic effects, (ii) $H_0$ values in the sub-samples (different anchor-based) in both R11 and R16 groups are significantly different at a 99\% confidence level, and (iii) neglecting the metal-rich MW sample does not reduce the $H_0$ value significantly, and thus Hubble tension persists. A small reduction in the Hubble constant could be linked to the differences in the host environment. Hence instead of using a single universal relation environment based slope and zero point should be preferred.Comment: 15 pages (single column), 7 figure

Effective interventional approach to control anaemia in pregnant women

Anaemia in pregnancy and low birth weight babies, a serious public health problem, troubles India and several other nations. This article reports the results of a approach to address the issue. Women up to 20 week pregnancy with haemoglobin (Hb) 9.0 g/dl or less, those with urinary fluoride beyond 1.0 mg/l and not suffering from any other ailments, were selected. Out of the 205 pregnant women attending antenatal clinics (ANCs) during 1st and 2nd trimesters, the sample and control groups were selected through computerized random sampling procedure. Ninety pregnant women formed the sample group and 115 formed the control group. The sample group was introduced to two interventions, viz.: (1) removal of fluoride from ingestion through drinking water, food and other sources, (2) counselling based intake of essential nutrients, viz. calcium, iron, folic acid, vitamins C, E and other antioxidants through dairy products, vegetables and fruits. No intervention was introduced for the control group. Sample and control groups were monitored for urinary fluoride and Hb until delivery during their visits to ANC. Birth weight of the babies were recorded from the labour room register. Results reveal that (1) the urine fluoride levels decreased in 67% and 53% of the pregnant women respectively, who attended ANCs during 1st and 2nd trimester of pregnancy. (2) An increase in Hb upon withdrawal of fluoride followed by nutritional intervention in 73% and 83% respectively has also been recorded. (3) Body mass index (BMI) also enhanced. (4) The percentage of pre-term deliveries was decreased in sample group compared to control. (5) Birth weight of babies enhanced in 80% and 77% in sample group women who attended ANC in 1st and 2nd trimester respectively as opposed to 49% and 47% respectively in the control group. (6) The number of low birth weight babies was reduced to 20% and 23% respectively in sample as opposed to 51% and 53% in control groups

Direction Dependence in Supernova Data: Constraining Isotropy

We revise and extend the extreme value statistic, introduced in \cite{gup08}, to study directional dependence in the high redshift supernova data; arising either from departures from the cosmological principle or due to direction dependent statistical systematics in e data. We introduce a likelihood function that analytically marginalises over the Hubble constant, and use it to extend our previous statistic. We also introduce a new statistic that is sensitive to direction dependence arising from living off-centre inside a large void, as well as previously mentioned reasons for anisotropy. We show that for large data sets this statistic has a limiting form that can be computed analytically. We apply our statistics to the gold data sets from \cite{rie04} and \cite{rie07}, as in our previous work. Our revision and extension of previous statistic shows that 1) the effect of marginalsing over Hubble constant instead of using its best fit value has only a marginal effect on our results. However, correction of errors in our previous work reduce the level of non-Gaussianity in the 2004 gold data that was found in our earlier work. The revised results for the 2007 gold data show that the data is consistent with isotropy and Gaussianity. Our second statistic confirms these results.Comment: 8 pages, 6 figures. Accepted for publication in MNRA