Acceptance dependence of fluctuation measures near the QCD critical point

We argue that a crucial determinant of the acceptance dependence of fluctuation measures in heavy-ion collisions is the range of correlations in the momentum space, e.g., in rapidity, $\Delta y_{\rm corr}$. The value of $\Delta y_{\rm corr}\sim1$ for critical thermal fluctuations is determined by the thermal rapidity spread of the particles at freezeout, and has little to do with position space correlations, even near the critical point where the spatial correlation length $\xi$ becomes as large as $2-3$ fm (this is in contrast to the magnitudes of the cumulants, which are sensitive to $\xi$). When the acceptance window is large, $\Delta y\gg\Delta y_{\rm corr}$, the cumulants of a given particle multiplicity, $\kappa_k$, scale linearly with $\Delta y$, or mean multiplicity in acceptance, $\langle N\rangle$, and cumulant ratios are acceptance independent. While in the opposite regime, $\Delta y\ll\Delta y_{\rm corr}$, the factorial cumulants, $\hat\kappa_k$, scale as $(\Delta y)^k$, or $\langle N\rangle^k$. We demonstrate this general behavior quantitatively in a model for critical point fluctuations, which also shows that the dependence on transverse momentum acceptance is very significant. We conclude that extension of rapidity coverage proposed by STAR should significantly increase the magnitude of the critical point fluctuation signatures.Comment: 9 pages, 4 figures, references adde

Chiral topological insulator of magnons

We propose a magnon realization of 3D topological insulator in the AIII (chiral symmetry) topological class. The topological magnon gap opens due to the presence of Dzyaloshinskii-Moriya interactions. The existence of the topological invariant is established by calculating the bulk winding number of the system. Within our model, the surface magnon Dirac cone is protected by the sublattice chiral symmetry. By analyzing the magnon surface modes, we confirm that the backscattering is prohibited. By weakly breaking the chiral symmetry, we observe the magnon Hall response on the surface due to opening of the gap. Finally, we show that by changing certain parameters the system can be tuned between the chiral topological insulator (mcTI), three dimensional magnon anomalous Hall (3D-mAH), and Weyl magnon phases.Comment: 6 page

Anomalous Josephson effect in d-wave superconductor junctions on TI surface

We study Josephson effect of $d$-wave superconductor (DS)/ferromagnet insulator(FI)/DS junctions on a surface of topological insulator (TI). We calculate Josephson current $I\left(\varphi \right)$ for various orientations of the junctions where $\varphi$ is the macroscopic phase difference between two DSs. In certain configurations, we find anomalous current-phase relation $I(\varphi)=-I\left( -\varphi +\pi \right)$ with $2\pi$ periodicity. In the case where the first order Josephson coupling is absent without magnetization in FI, $I(\varphi)$ can be proportional to $\cos \varphi$. The magnitude of the obtained Josephson current is enhanced due to the zero energy states on the edge of DS on TI. Even if we introduce an $s$-wave component of pair potential in DS, we can still expect the anomalous current-phase relation in asymmetric DS junctions with $I\left( \varphi =0\right) \neq 0$. This can be used to probe the induced $d$-wave component of pair potential on TI surface in high-$T_{c}$ cuperate/TI hybrid structures.Comment: 6 pages, 4 figure

Integration of Elymus repens control and post-harvest catch crop growing in organic cropping systems

In Northern Europe, Elymus repens (L.) Gould infestations are traditionally controlled by repeated stubble cultivation in the period from harvest to ploughing in autumn. However, in organic farming, post-harvest tillage is undesirable due to the need for retaining nutrients in the cropping system. The soil is mostly cropped in that period, limiting post-harvest tillage. Two control strategies against E. repens are presented that merge the objectives of achieving a significant reduction of E. repens while having the soil covered with plants during the post-harvest period. Strategy I is an integration of rhizome fragmentation by soil cultivation within two days after harvest in early August with subsequent sowing of a catch crop to suppress shoot growth from the rhizome fragments. Strategy II also includes growing a catch crop but is preceded by a mid-summer fallow period lasting 4-6 weeks where repeated soil cultivations are conducted to fragment, weaken and desiccate the rhizomes. Strategy II controlled 91-90% of the E. repens population while strategy I only controlled up to 40%, mainly because of the weakening and desiccation of rhizomes caused by repeated cultivations. However, the fallow period may lead to undesirable nutrient leaching from sandy soils and the grower will have to desist from growing a profitable maturing crop, aspects that should be counterbalanced against the urgency for E. repens control and other possible control options. Strategy I appears to be more relevant for low infestation levels of E. repens while strategy II would be more appropriate where infestations have become large

Diffractive optics approach towards subwavelength pixels

Pixel size in cameras and other refractive imaging devices is typically limited by the free-space diffraction. However, a vast majority of semiconductor-based detectors are based on materials with substantially high refractive index. We demonstrate that diffractive optics can be used to take advantage of this high refractive index to reduce effective pixel size of the sensors below free-space diffraction limit. At the same time, diffractive systems encode both amplitude and phase information about the incoming beam into multiple pixels, offering the platform for noise-tolerant imaging with dynamical refocusing. We explore the opportunities opened by high index diffractive optics to reduce sensor size and increase signal-to-noise ratio of imaging structures.Comment: submitted to SPIE-DCS 201

Three `species' of Schr\"odinger cat states in an infinite-range spin model

We explore a transverse-field Ising model that exhibits both spontaneous symmetry-breaking and eigenstate thermalization. Within its ferromagnetic phase, the exact eigenstates of the Hamiltonian of any large but finite-sized system are all Schr\"odinger cat states: superpositions of states with `up' and `down' spontaneous magnetization. This model exhibits two dynamical phase transitions {\it within} its ferromagnetic phase: In the lowest-temperature phase the magnetization can macroscopically oscillate between up and down. The relaxation of the magnetization is always overdamped in the remainder of the ferromagnetic phase, which is divided in to phases where the system thermally activates itself {\it over} the barrier between the up and down states, and where it quantum tunnels.Comment: 7 pages, added numerical result