Wormhole inspired by non-commutative geometry

In the present work we search for a new wormhole solution inspired by noncommutative geometry with the additional condition of allowing conformal Killing vectors (CKV). A special aspect of noncommutative geometry is that it replaces point-like structures of gravitational sources with smeared objects under Gaussian distribution. However, the purpose of this paper is to obtain wormhole solutions with noncommutative geometry as a background where we consider a point-like structure of gravitational object without smearing effect. It is found through this investigation that wormhole solutions exist in this Lorentzian distribution with viable physical properties.Comment: 15 pages, 6 figures, 1 table, Substantial modifications in the whole manuscript, Accepted in Phys. Lett.

Security Vulnerabilities in Smart Contracts as Specifications in Linear Temporal Logic

Ethereum is a distributed computer with a native cryptocurrency. Like other monetary transaction based systems, a problem this platform faces is accounts and transactions being susceptible to theft and other hacks. Smart contracts (programs which run on this blockchain) can store money and initiate financial transactions. They need to be carefully studied to safeguard against threats. This is especially true before deployment, as they become immutable after. Software analysis and verification techniques are applied to study security vulnerabilities in smart contracts. Currently, there are over 35 tools that do so. Many of them directly study contracts written in high level languages such as Solidity. In this work, we similarly study contracts, but at the lower bytecode level. We focus on different classes of smart contract vulnerabilities– access control, bad randomness, denial of service, front running, integer overflow/underflow, re-entrancy, short address, time manipulation, and unchecked low-level calls. We create specifications based on linear temporal logic to describe vulnerabilities in each of these categories, and we test them against real-world contracts

Analysis of Offset Pulse Position Modulation

This work presents the performance analysis of the offset pulse position modulation (PPM) scheme using graded-index plastic optical fibre with a Gaussian impulse response. The aim of this analysis is to predict how sensitivity, error, number of required photons, threshold voltage, and the effect of inter-symbol interference will change with the change in the number of data bits encoded at a rate of 1 Gbit/s. An information theory analysis is presented in detail and also the band-utilization efficiency is determined. Results are compared to equivalent digital PPM and multiple PPM schemes and it is also shown that offset PPM gives an advantage over on-off keying (OOK). Bit error rate (BER) analysis has been presented numerically. The errors due to different coding techniques are compared. It has also been shown that offset pulse position modulation is more power efficient than multiple pulse position modulation. The spectral analysis of offset pulse position modulation coding scheme has been carried out. For an offset PPM sequence the spectral characteristics is presented both theoretically and numerically. The results show strong frequency components at the frame rate and, if return-to-zero pulses are used, the slot rate. Slot synchronisation has been taken into consideration for the first time as offset PPM spectrum exhibits discrete slot rate component. The effect of pulse shaping and modulating index on the spectrum has been shown. The dependency of slot component on the pulse shape is examined. The results show that the frame synchronisation is possible for offset PPM as this coding exhibits a strong frame rate component. A comparison of spectral characteristics has been presented considering digital, multiple and shortened PPM. For ease of implementation an offset PPM coder has been designed. In this work an efficient clock recovery topology is presented for offset PPM data sequence at the receiver end. For clock recovery, a phase locked loop is designed. Data recovery has also been presented. It is shown that a frame clock can be extracted from the data sequence that yields the possibility of frame synchronization. A detailed noise analysis has been performed for random offset PPM input. It has been shown that the proposed clock recovery system is also effective for extracting other data sequence. To elucidate, a multiple Pulse Position Modulation (MPPM) data sequence is considered. The MPPM data sequence has also been synchronised with the recovered clock. A noise analysis is carried out for multiple PPM

Detection of biomarker in breath: A step towards noninvasive diabetes monitoring

Along with more than two hundred volatile organic compounds (VOCs), acetone is also a normal constituent of breath of healthy individuals, albeit in the sub-ppm range, and its concentration increases in diabetic patients. Considering the importance of breath acetone as a biomarker of diabetes, some studies have already been made to measure breath acetone concentration (and correlate with blood sugar level) using GC-MS. There are a few reports of measuring breath acetone concentration using semiconductor sensor in the background of air (i.e. in the absence of VOCs present in normal breath and hence the question of selectivity remains in the real situation) and at a higher concentration (above 10 ppm). We report excellent sensitivity of sonochemically prepared nanosized gamma-Fe2O3 sensors towards sub-ppm acetone (pathological range) in the background of human breath. Our preliminary results should stimulate further research towards developing cheap, rugged and compact semiconductor sensors for noninvasive monitoring of diabetes

Strange stars in Krori-Barua space-time

The singularity space-time metric obtained by Krori and Barua\cite{Krori1975} satisfies the physical requirements of a realistic star. Consequently, we explore the possibility of applying the Krori and Barua model to describe ultra-compact objects like strange stars. For it to become a viable model for strange stars, bounds on the model parameters have been obtained. Consequences of a mathematical description to model strange stars have been analyzed.Comment: 9 pages (two column), 12 figures. Some changes have been made. " To appear in European Physical Journal C