Two ultracold atoms in a completely anisotropic trap

As a limiting case of ultracold atoms trapped in deep optical lattices, we consider two interacting atoms trapped in a general anisotropic harmonic oscillator potential, and obtain exact solutions of the Schrodinger equation for this system. The energy spectra for different geometries of the trapping potential are compared.Comment: 4 pages, 2 figure

Physical Layer Security for Massive MIMO Systems Impaired by Phase Noise

In this paper, we investigate the impact of phase noise on the secrecy performance of downlink massive MIMO systems in the presence of a passive multiple-antenna eavesdropper. Thereby, for the base station (BS) and the legitimate users, the effect of multiplicative phase noise is taken into account, whereas the eavesdropper is assumed to employ ideal hardware. We derive a lower bound for the ergodic secrecy rate of a given user when matched filter data precoding and artificial noise transmission are employed at the BS. Based on the derived analytical expression, we investigate the impact of the various system parameters on the secrecy rate. Our analytical and simulation results reveal that distributively deployed local oscillators (LOs) can achieve a better performance than one common LO for all BS antennas as long as a sufficient amount of power is assigned for data transmission.Comment: Invited paper, submitted to IEEE SPAWC 201

Secure Transmission in Multi-Cell Massive MIMO Systems

In this paper, we consider physical layer security provisioning in multi-cell massive multiple-input multiple-output (MIMO) systems. Specifically, we consider secure downlink transmission in a multi-cell massive MIMO system with matched-filter precoding and artificial noise (AN) generation at the base station (BS) in the presence of a passive multi-antenna eavesdropper. We investigate the resulting achievable ergodic secrecy rate and the secrecy outage probability for the cases of perfect training and pilot contamination. Thereby, we consider two different AN shaping matrices, namely, the conventional AN shaping matrix, where the AN is transmitted in the null space of the matrix formed by all user channels, and a random AN shaping matrix, which avoids the complexity associated with finding the null space of a large matrix. Our analytical and numerical results reveal that in multi-cell massive MIMO systems employing matched-filter precoding (1) AN generation is required to achieve a positive ergodic secrecy rate if the user and the eavesdropper experience the same path-loss, (2) even with AN generation secure transmission may not be possible if the number of eavesdropper antennas is too large and not enough power is allocated to channel estimation, (3) for a given fraction of power allocated to AN and a given number of users, in case of pilot contamination, the ergodic secrecy rate is not a monotonically increasing function of the number of BS antennas, and (4) random AN shaping matrices provide a favourable performance/complexity tradeoff and are an attractive alternative to conventional AN shaping matrices

Regulatory Focus and Interdependent Economic Decision-Making

Traditional theories of self-interest cannot predict when individuals pursue relative and absolute economic outcomes in interdependent decision-making, but we argue that regulatory focus (Higgins, 1997) can. We propose that a concern with security (prevention focus) motivates concerns with social status, leading to the regulation of relative economic outcomes, but a concern with growth (promotion focus) motivates the maximization of opportunities, leading to a focus on absolute outcomes. Two studies supported our predictions; regardless of prosocial or proself motivations, a promotion focus yielded greater concern with absolute outcomes, but a prevention focus yielded greater concern with relative outcomes. Also, Study 3 revealed that a prevention focus led to a greater rejection of a negative relative but positive absolute outcome in an ultimatum game because of concerns with status. This research reveals that apparently opposing orientations to interdependence – equality and relative gain – serve the same self-regulatory purpose: the establishment of security