Optical emission investigation of laser-produced MgB2 plume expanding in an Ar buffer gas

Optical emission spectroscopy is used to study the dynamics of the plasma generated by pulsed-laser irradiation of a MgB2 target, both in vacuum and at different Ar buffer gas pressures. The analysis of the time-resolved emission of selected species shows that the Ar background gas strongly influences the plasma dynamics. Above a fixed pressure, plasma propagation into Ar leads to the formation of blast waves causing both a considerable increase of the fraction of excited Mg atoms and a simultaneous reduction of their kinetic flux energy. These results can be particularly useful for optimizing MgB2 thin film deposition processes.Comment: 11 pages,4 figures, Applied Physics Letters in pres

Scalings of domain wall energies in two dimensional Ising spin glasses

We study domain wall energies of two dimensional spin glasses. The scaling of these energies depends on the model's distribution of quenched random couplings, falling into three different classes. The first class is associated with the exponent theta =-0.28, the other two classes have theta = 0, as can be justified theoretically. In contrast to previous claims, we find that theta=0 does not indicate d=d_l but rather d <= d_l, where d_l is the lower critical dimension.Comment: Clarifications and extra reference

“Left and right prefrontal routes to action comprehension”

Successful action comprehension requires the integration of motor information and semantic cues about objects in context. Previous evidence suggests that while motor features are dorsally encoded in the fronto-parietal action observation network (AON); semantic features are ventrally processed in temporal structures. Importantly, these dorsal and ventral routes seem to be preferentially tuned to low (LSF) and high (HSF) spatial frequencies, respectively. Recently, we proposed a model of action comprehension where we hypothesized an additional route to action understanding whereby coarse LSF information about objects in context is projected to the dorsal AON via the prefrontal cortex (PFC), providing a prediction signal of the most likely intention afforded by them. Yet, this model awaits for experimental testing. To this end, we used a perturb-and-measure continuous theta burst stimulation (cTBS) approach, selectively disrupting neural activity in the left and right PFC and then evaluating the participant's ability to recognize filtered action stimuli containing only HSF or LSF. We find that stimulation over PFC triggered different spatial-frequency modulations depending on lateralization: left-cTBS and right-cTBS led to poorer performance on HSF and LSF action stimuli, respectively. Our findings suggest that left and right PFC exploit distinct spatial frequencies to support action comprehension, providing evidence for multiple routes to social perception in humans

Subextensive singularity in the 2D ±J\pm J Ising spin glass

The statistics of low energy states of the 2D Ising spin glass with +1 and -1 bonds are studied for $L \times L$ square lattices with $L \le 48$, and $p$ = 0.5, where $p$ is the fraction of negative bonds, using periodic and/or antiperiodic boundary conditions. The behavior of the density of states near the ground state energy is analyzed as a function of $L$, in order to obtain the low temperature behavior of the model. For large finite $L$ there is a range of $T$ in which the heat capacity is proportional to $T^{5.33 \pm 0.12}$. The range of $T$ in which this behavior occurs scales slowly to $T = 0$ as $L$ increases. Similar results are found for $p$ = 0.25. Our results indicate that this model probably obeys the ordinary hyperscaling relation $d \nu = 2 - \alpha$, even though $T_c = 0$. The existence of the subextensive behavior is attributed to long-range correlations between zero-energy domain walls, and evidence of such correlations is presented.Comment: 13 pages, 7 figures; final version, to appear in J. Stat. Phy

Pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3: plasma plume effects

Pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3 interfaces has been analyzed with a focus on the kinetic energy of the ablated species. LaGaO3 and LaAlO3 plasma plumes were studied by fast photography and space-resolved optical emission spectroscopy. Reflection high energy electron diffraction was performed proving a layer-by-layer growth up to 10-1 mbar oxygen pressure. The role of the energetic plasma plume on the two-dimensional growth and the presence of interfacial defects at different oxygen growth pressure has been discussed in view of the conducting properties developing at such polar/non-polar interfaces

Static Properties of Trapped Bose-Fermi Mixed Condensate of Alkali Atoms

Static properties of a bose-fermi mixture of trapped potassium atoms are studied in terms of coupled Gross-Pitaevskii and Thomas-Fermi equations for both repulsive and attractive bose-fermi interatomic potentials. Qualitative estimates are given for solutions of the coupled equations, and the parameter regions are obtained analytically for the boson-density profile change and for the boson/fermion phase separation. Especially, the parameter ratio $R_{int}$ is found that discriminates the region of the large boson-profile change. These estimates are applied for numerical results for the potassium atoms and checked their consistency. It is suggested that a small fraction of fermions could be trapped without an external potential for the system with an attractive boson-fermion interaction.Comment: 8 pages,5 figure

Zero sound in a single component fermion - Bose Einstein Condensate mixture

The resonant dynamics of mediated interactions supports zero-sound in a cold atom degenerate mixture of a single component fermion gas and a Bose-Einstein condensate (BEC). We characterize the onset of instability in the phase separation of an unstable mixture and we find a rich collective mode structure for stable mixtures with one undamped mode that exhibits an avoided crossing and a Landau-damped mode that terminates.Comment: 4 pages, 2 figure

A Web Infrastructure for Certifying Multimedia News Content for Fake News Defense

In dealing with altered visual multimedia content, also referred to as fake news, we present a ready-to-deploy extension of the current public key infrastructure (PKI), to provide an endorsement and integrity check platform for newsworthy visual multimedia content. PKI, which is primarily used for Web domain authentication, can directly be utilized with any visual multimedia file. Unlike many other fake news researches that focus on technical multimedia data processing and verification, we enable various news organizations to use our developed program to certify/endorse a multimedia news content when they believe this news piece is truthiness and newsworthy. Our program digitally signs the multimedia news content with the news organization's private key, and the endorsed news content can be posted not only by the endorser, but also by any other websites. By installing a web browser extension developed by us, an end user can easily verify whether a multimedia news content has been endorsed and by which organization. During verification, our browser extension will present to the end user a floating logo next to the image or video. This logo, in the shape of a shield, will show whether the image has been endorsed, by which news organization, and a few more pieces of essential text information of the news multimedia content. The proposed system can be easily integrated to other closed-web system such as social media networks and easily applied to other non-visual multimedia files.Comment: 7 pages, 6 figure

Temperature Chaos in Two-Dimensional Ising Spin Glasses with Binary Couplings: a Further Case for Universality

We study temperature chaos in a two-dimensional Ising spin glass with random quenched bimodal couplings, by an exact computation of the partition functions on large systems. We study two temperature correlators from the total free energy and from the domain wall free energy: in the second case we detect a chaotic behavior. We determine and discuss the chaos exponent and the fractal dimension of the domain walls.Comment: 5 pages, 6 postscript figures; added reference

Miscibility in a degenerate fermionic mixture induced by linear coupling

We consider a one-dimensional mean-field-hydrodynamic model of a two-component degenerate Fermi gas in an external trap, each component representing a spin state of the same atom. We demonstrate that the interconversion between them (linear coupling), imposed by a resonant electromagnetic wave, transforms the immiscible binary gas into a miscible state, if the coupling constant, $\kappa$, exceeds a critical value, $\kappa _{\mathrm{cr}}$. The effect is predicted in a variational approximation, and confirmed by numerical solutions. Unlike the recently studied model of a binary BEC with the linear coupling, the components in the immiscible phase of the binary fermion mixture never fill two separated domains with a wall between them, but rather form anti-locked ($\pi$ -phase-shifted) density waves. Another difference from the bosonic mixture is spontaneous breaking of symmetry between the two components in terms of numbers of atoms in them, $N_{1}$ and $N_{2}$. The latter effect is characterized by the parameter $\nu \equiv (N_{1}-N_{2})/(N_{1}+N_{2})$ (only $N_{1}+N_{2}$ is a conserved quantity), the onset of miscibility at $\kappa \geq \kappa_{\mathrm{cr}}$ meaning a transition to $\nu \equiv 0$. At $\kappa <\kappa_{\mathrm{cr}}$, $\nu$ features damped oscillations as a function of $\kappa$. We also briefly consider an asymmetric model, with a chemical-potential difference between the two components.Comment: 9 pages, 12 figures, PRA (in press