Analyzing the Bitcoin Ponzi Scheme Ecosystem

This paper analyzes the supply and demand for Bitcoinbased Ponzi schemes. There are a variety of these types of scams: from long cons such as Bitcoin Savings & Trust to overnight doubling schemes that do not take off. We investigate what makes some Ponzi schemes successful and others less so. By scouring 11 424 threads on bitcointalk.org, we identify 1 780 distinct scams. Of these, half lasted a week or less. Using survival analysis, we identify factors that affect scam persistence. One approach that appears to elongate the life of the scam is when the scammer interacts a lot with their victims, such as by posting more than a quarter of the comments in the related thread. By contrast, we also find that scams are shorter-lived when the scammers register their account on the same day that they post about their scam. Surprisingly, more daily posts by victims is associated with the scam ending sooner

Magnetotransport in graphene on silicon side of SiC

We have studied the transport properties of graphene grown on silicon side of SiC. Samples under study have been prepared by two different growth methods in two different laboratories. Magnetoresistance and Hall resistance have been measured at temperatures between 4 and 100 K in resistive magnet in magnetic fields up to 22 T. In spite of differences in sample preparation, the field dependence of resistances measured on both sets of samples exhibits two periods of magneto-oscillations indicating two different parallel conducting channels with different concentrations of carriers. The semi-quantitative agreement with the model calculation allows for conclusion that channels are formed by high-density and low-density Dirac carriers. The coexistence of two different groups of carriers on the silicon side of SiC was not reported before.Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of Physics: Conference series" as a contribution to the proceedings of the 20th International Conference on "High Magnetic Fields in Semiconductor Physics", HMF 2

Short Paper: An Exploration of Code Diversity in the Cryptocurrency Landscape

Interest in cryptocurrencies has skyrocketed since their introduction a decade ago, with hundreds of billions of dollars now invested across a landscape of thousands of different cryptocurrencies. While there is significant diversity, there is also a significant number of scams as people seek to exploit the current popularity. In this paper, we seek to identify the extent of innovation in the cryptocurrency landscape using the open-source repositories associated with each one. Among other findings, we observe that while many cryptocurrencies are largely unchanged copies of Bitcoin, the use of Ethereum as a platform has enabled the deployment of cryptocurrencies with more diverse functionalities

Impurity-induced diffusion bias in epitaxial growth

We introduce two models for the action of impurities in epitaxial growth. In the first, the interaction between the diffusing adatoms and the impurities is ``barrier''-like and, in the second, it is ``trap''-like. For the barrier model, we find a symmetry breaking effect that leads to an overall down-hill current. As expected, such a current produces Edwards-Wilkinson scaling. For the trap model, no symmetry breaking occurs and the scaling behavior appears to be of the conserved-KPZ type.Comment: 5 pages(with the 5 figures), latex, revtex3.0, epsf, rotate, multico

Computational method for obtaining filiform Lie algebras of arbitrary dimension

This paper shows a new computational method to obtain filiform Lie algebras, which is based on the relation between some known invariants of these algebras and the maximal dimension of their abelian ideals. Using this relation, the law of each of these algebras can be completely determined and characterized by means of the triple consisting of its dimension and the invariants z1 and z2. As examples of application, we have included a table showing all valid triples determining filiform Lie algebras for dimension 13

Density-functional study of hydrogen chemisorption on vicinal Si(001) surfaces

Relaxed atomic geometries and chemisorption energies have been calculated for the dissociative adsorption of molecular hydrogen on vicinal Si(001) surfaces. We employ density-functional theory, together with a pseudopotential for Si, and apply the generalized gradient approximation by Perdew and Wang to the exchange-correlation functional. We find the double-atomic-height rebonded D_B step, which is known to be stable on the clean surface, to remain stable on partially hydrogen-covered surfaces. The H atoms preferentially bind to the Si atoms at the rebonded step edge, with a chemisorption energy difference with respect to the terrace sites of >sim 0.1 eV. A surface with rebonded single atomic height S_A and S_B steps gives very similar results. The interaction between H-Si-Si-H mono-hydride units is shown to be unimportant for the calculation of the step-edge hydrogen-occupation. Our results confirm the interpretation and results of the recent H_2 adsorption experiments on vicinal Si surfaces by Raschke and Hoefer described in the preceding paper.Comment: 13 pages, 8 figures, submitted to Phys. Rev. B. Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

A particular type of non-associative algebras and graph theory

Evolution algebras have many connections with other mathematical fields, like group theory, stochastics processes, dynamical systems and other related ones. The main goal of this paper is to introduce a novel non-usual research on Discrete Mathematics regarding the use of graphs to solve some open problems related to the theory of graphicable algebras, which constitute a subset of those algebras. We show as many our advances in this field as other non solved problems to be tackled in future

Low-dimensional filiform Lie algebras over finite fields

In this paper we use some objects of Graph Theory to classify low-dimensional filiform Lie algebras over finite fields. The idea lies in the representation of each Lie algebra by a certain type of graphs. Then, some properties on Graph Theory make easier to classify the algebras. As results, which can be applied in several branches of Physics or Engineering, for instance, we find out that there exist, up to isomorphism, six 6-dimensional filiform Lie algebras over Z/pZ, for p = 2, 3, 5.Plan Andaluz de Investigación (Junta de Andalucía

Guided vortex motion in superconductors with a square antidot lattice

We have measured the in-plane anisotropy of the vortex mobility in a thin Pb film with a square array of antidots. The Lorentz force, acting on the vortices, was rotated by adding two perpendicular currents and keeping the amplitude of the net current constant. One set of voltage probes was used to detect the vortex motion. We show that the pinning landscape provided by the square antidot lattice influences the vortex motion in two different ways. First, the modulus of the vortex velocity becomes angular dependent with a lower mobility along the diagonals of the pinning array. Second, the vortex displacement is preferentially parallel to the principal axes of the underlying pinning lattice, giving rise to a misalignment between the vortex velocity and the applied Lorentz force. We show that this anisotropic vortex motion is temperature dependent and progressively fades out when approaching the normal state.Comment: 5 pages, 4 figure