arXiv subjects

G. Konstantinidis

Publications and source records attributed to G. Konstantinidis.

4 recordsLinked to original sources

arXiv2018

Selfish Cops and Active Robber: Multi-Player Pursuit Evasion on Graphs

We introduce and study the game of "Selfish Cops and Active Robber" (SCAR) which can be seen as an multiplayer variant of the "classic" two-player Cops and Robbers (CR) game. In classic CR all cops are controlled by a single player, who has no preference over which cop captures the robber. In SCAR, on the other hand, each of N-1 cops is controlled by a separate player, and a single robber is controlled by the N-th player; and the capturing cop player receives a higher reward than the non-capturing ones. Consequently, SCAR is an N-player pursuit game on graphs, in which each cop player has an increased motive to be the one who captures the robber. The focus of our study is the existence and properties of SCAR Nash Equilibria (NE). In particular, we prove that SCAR always has one NE in deterministic positional strategies and (for N greater than two) another in deterministic nonpositional strategies. Furthermore, we study conditions which, at equilibrium, guarantee either capture or escape of the robber and show that (because of the antagonism between the "selfish" cop players) the robber may, in certain SCAR configurations, be captured later than he would be in classic CR, or even not captured at all. Finally we define the selfish cop number of a graph and study its connection to the classic cop number.

cs.DM↗

arXiv2014

Quantum coherence in momentum space of light-matter condensates

We show that the use of momentum-space optical interferometry, which avoids any spatial overlap between two parts of a macroscopic quantum state, presents a unique way to study coherence phenomena in polariton condensates. In this way, we address the longstanding question in quantum mechanics: "\emph{Do two components of a condensate, which have never seen each other, possess a definitive phase?}" [P. W. Anderson, \emph{Basic Notions of Condensed Matter Physics} (Benjamin, 1984)]. A positive answer to this question is experimentally obtained here for light-matter condensates, created under precise symmetry conditions, in semiconductor microcavities taking advantage of the direct relation between the angle of emission and the in-plane momentum of polaritons.

cond-mat.mes-hall↗

arXiv2013

Microwave and millimeterwave electrical permittivity of graphene monolayer

The effective electrical permittivity of a graphene monolayer is experimentally investigated in the 5-40 GHz range, which encompasses the microwave and the lower part of millimeterwave spectrum. The measurements were carried out using a coupled coplanar waveguide placed over a graphene monolayer flake, which is deposited on Si/SiO2. In contrast to some initial predictions, the effective permittivity of the graphene monolayer is slightly decreasing in the above-mentioned frequency range and has an average value of 3.3.

cond-mat.mes-hall↗

arXiv2012

Graphene-like metallic-on-silicon field effect transistor

In this manuscript, we present a field effect transistor with a channel consisting of a two-dimensional electron gas located at the interface between an ultrathin metallic film of Ni and a p-type Si(111) substrate. We have demonstrated that the two-dimensional electron gas channel is modulated by the gate voltage. The dependence of the drain current on the drain voltage has no saturation region, similar to a field effect transistor based on graphene. However, the transport in this transistor is not ambipolar, as in graphene, but unipolar.

cond-mat.mes-hall↗