Antikaons and higher order couplings in relativistic-mean field study of neutron stars

We investigate the role of higher order couplings, along with the condensation of antikaons ($K^-$ and $\bar K^0$), on the properties of neutron star (NS). We employ extended versions of the relativistic mean-field model, in which kaon-nucleon and nucleon-nucleon interactions are taken on the same footing. We find that the onset of condensation of $K^-$ and $\bar K^0$ highly depends not only on the strength of optical potential but also on the new couplings. The presence of antikaons leads to a softer equation of state and makes the neutron star core symmetric and lepton-deficient. We show that these effects strongly influence the mass-radius relation as well as the composition of neutron star. We also show that the recently observed 1.97$\pm$.04 solar mass NS can be explained in three ways: (i) a stiffer EoS with both antikaons, (ii) a relatively soft EoS with $K^-$ and (iii) a softer EoS without antikaons

Role of higher order couplings in the presence of kaons in relativistic mean field description of neutron stars

We discuss the role of higher order couplings in conjunction with kaon condensation using recent versions of relativistic mean field models.We focus on an interaction (G2) in which all the parameters are obtained by fitting the finite nuclear data and successfully applied to reproduce a variety of nuclear properties. Our results show that the higher order couplings play a significant role at higher densities where kaons dominate the behavior of the equation of state. We compare our results with other interactions (NLl, NL3, G1, and FSUGold) and show that the new couplings bring down the mass of a neutron star (NS), which is further reduced in the presence of kaons to yield results consistent with the present observational constraints. We show that the composition of the NS varies with the parameter sets.Comment: 10 pages, 11 figure

DO AUCTION BIDS BETRAY EXPECTATIONS-BASED REFERENCE DEPENDENT PREFERENCES? A TEST, EXPERIMENTAL EVIDENCE, AND ESTIMATES OF LOSS AVERSION

In this paper, we provide a novel experimental auction design that exploits an exogenous variation in the probability of winning to test for the presence of expectations-based reference dependent preferences. We prove that (i) in this design, (which is a one parameter modification of a Becker-de Groote-Marschak (BDM) auction), a lower probability of winning will cause a loss averse agent to bid lower, for a large range of intrinsic values for the object. Data from an experiment demonstrate the existence of this effect. The effect would be absent if preferences were 'standard', or if the status quo was the reference point. Thus we contribute to the nascent literature that empirically documents the importance of expectations as a source of reference points. (ii) We further prove that the experimental design enables unique identification of participants' value distribution and loss averse than men. Finally, as a contribution to experimental methodology, we prove that the BDM mechanism will underestimate loss averse participants' values, we quantify the underestimation, and we suggest methods to bound this bias.Auctions, Expectations, Loss Aversion, Reference dependence

bit.ly/malicious: Deep Dive into Short URL based e-Crime Detection

Existence of spam URLs over emails and Online Social Media (OSM) has become a massive e-crime. To counter the dissemination of long complex URLs in emails and character limit imposed on various OSM (like Twitter), the concept of URL shortening has gained a lot of traction. URL shorteners take as input a long URL and output a short URL with the same landing page (as in the long URL) in return. With their immense popularity over time, URL shorteners have become a prime target for the attackers giving them an advantage to conceal malicious content. Bitly, a leading service among all shortening services is being exploited heavily to carry out phishing attacks, work-from-home scams, pornographic content propagation, etc. This imposes additional performance pressure on Bitly and other URL shorteners to be able to detect and take a timely action against the illegitimate content. In this study, we analyzed a dataset of 763,160 short URLs marked suspicious by Bitly in the month of October 2013. Our results reveal that Bitly is not using its claimed spam detection services very effectively. We also show how a suspicious Bitly account goes unnoticed despite of a prolonged recurrent illegitimate activity. Bitly displays a warning page on identification of suspicious links, but we observed this approach to be weak in controlling the overall propagation of spam. We also identified some short URL based features and coupled them with two domain specific features to classify a Bitly URL as malicious or benign and achieved an accuracy of 86.41%. The feature set identified can be generalized to other URL shortening services as well. To the best of our knowledge, this is the first large scale study to highlight the issues with the implementation of Bitly's spam detection policies and proposing suitable countermeasures.Comment: arXiv admin note: substantial text overlap with arXiv:1405.151