Spontaneous breaking of the Fermi surface symmetry in the t-J model: a numerical study

We present a variational Monte Carlo (VMC) study of spontaneous Fermi surface symmetry breaking in the t-J model. We find that the variational energy of a Gutzwiller projected Fermi sea is lowered by allowing for a finite asymmetry between the x- and the y-directions. However, the best variational state remains a pure superconducting state with d-wave symmetry, as long as the underlying lattice is isotropic. Our VMC results are in good overall agreement with slave boson mean field theory (SBMFT) and renormalized mean field theory (RMFT), although apparent discrepancies do show up in the half-filled limit, revealing some limitations of mean field theories. VMC and complementary RMFT calculations also confirm the SBMFT predictions that many-body interactions can enhance any anisotropy in the underlying crystal lattice. Thus, our results may be of consequence for the description of strongly correlated superconductors with an anisotropic lattice structure.Comment: 6 pages, 7 figures; final versio

Management of Root-Knot Nematodes (Meloidogyne Spp) on Tomato using Antagonistic Plants

African marigold (Tagetes erecta) and Crotalaria juncea were used as intercrops to control root knot nematodes on a susceptible tomato cultivar, Ibadan local in a pot experiment at the roof top of Crop Protection and Environmental Biology Dept, University of Ibadan, Ibadan, Oyo State, Nigeria. Four weeks old tomato plants intercropped with African marigold (Tagetes erecta) and Crotalaria juncea were inoculated with 5000eggs of root knot nematodes. Results indicated that absence of marigold or Crotalaria plants in the inoculated treatments led to increase in the number of second stage juvenile of root knot nematodes. The antagonistic plants produced significant reduction (P<0.05) in the root gall indices, reproductive factor and final nematode population in susceptible tomato plants roots. However, no significant differences were observed across the treatments in terms of mean number of leaves and plant heights. The results obtained have important implications for the design of alternative nematode management strategies using antagonistic plants. Keywords: antagonistic plants, root-knot nematodes, Gall index, Reproductive factor

Variasi Genetik Troides Helena (Lepidoptera: Papilionidae) Berdasarkan Gen COI (Cytochrome C Oxydase I)

Kupu-kupu Troides helena (Kupu-kupu Raja) merupakan salah satu spesies langka yang dilindungi. Eksploitasi yang berlebihan, serta alih fungsi hutan menjadi ancaman bagi kehidupan kupu-kupu ini. Penelitian ini dilakukan untuk mengetahui variasi pada gen cytochrome C oxidase I Troides helena yang diperoleh dari dua lokasi yang berbeda, yaitu Gunung Tumpa dan Gunung Dua-sudara. Analisis sekuens menunjukkan adanya perbedaan satu pasang basa nukleotida dari kedua spesimen tersebut. Selain itu, variasi juga ditunjukan pada sampel yang diperoleh dari basis data GenBank dengan adanya perbedaan 7-8 pasang basa nukleotida dengan spesimen pada penelitian ini. Hasil perhitungan jarak genetik menunjukkan bahwa meskipun secara geografis spesimen-spesimen uji ini berasal dari lokasi yang berjauhan, variasi genetik masih berada dalam kisaran variasi intraspesies.Troides helena (Common Birdwing) is listed as one of endangered and protected butterfly species. Excessive exploitation and forest conversion have become threat to the life of this butterfly. This study was conducted to determine the genetic variation of Troides helena obtained from Mt. Tumpa and Mt. Dua-sudara based on cytochrome C oxidase I gene. Sequence analysis shows one nucleotide difference between these two specimens. Moreover, genetic variation also has been shown by comparing these two specimen with other Troides helena obtained from database in GenBank. There are 7-8 nucleotides differences among tested specimens. The result of genetic distance calculations indicates that although geographically these test specimens derived from remote locations, the genetic variation is still within the range of intraspecific variation

REAL: Resilience and Adaptation using Large Language Models on Autonomous Aerial Robots

Large Language Models (LLMs) pre-trained on internet-scale datasets have shown impressive capabilities in code understanding, synthesis, and general purpose question-and-answering. Key to their performance is the substantial prior knowledge acquired during training and their ability to reason over extended sequences of symbols, often presented in natural language. In this work, we aim to harness the extensive long-term reasoning, natural language comprehension, and the available prior knowledge of LLMs for increased resilience and adaptation in autonomous mobile robots. We introduce REAL, an approach for REsilience and Adaptation using LLMs. REAL provides a strategy to employ LLMs as a part of the mission planning and control framework of an autonomous robot. The LLM employed by REAL provides (i) a source of prior knowledge to increase resilience for challenging scenarios that the system had not been explicitly designed for; (ii) a way to interpret natural-language and other log/diagnostic information available in the autonomy stack, for mission planning; (iii) a way to adapt the control inputs using minimal user-provided prior knowledge about the dynamics/kinematics of the robot. We integrate REAL in the autonomy stack of a real multirotor, querying onboard an offboard LLM at 0.1-1.0 Hz as part the robot's mission planning and control feedback loops. We demonstrate in real-world experiments the ability of the LLM to reduce the position tracking errors of a multirotor under the presence of (i) errors in the parameters of the controller and (ii) unmodeled dynamics. We also show (iii) decision making to avoid potentially dangerous scenarios (e.g., robot oscillates) that had not been explicitly accounted for in the initial prompt design.Comment: 13 pages, 5 figures, conference worksho

The spin 1/2 Heisenberg star with frustration II: The influence of the embedding medium

We investigate the spin 1/2 Heisenberg star introduced in J. Richter and A. Voigt, J. Phys. A: Math. Gen. {\bf 27}, 1139 (1994). The model is defined by $H=J_1 \sum_{i=1}^{N}{{\bf s}_0{\bf s}_i} + J_2 H_{R}\{{\bf s}_i\}$ ; $J_1,J_2 \ge 0$ , $i=1,...,N$. In extension to the Ref. we consider a more general $H_{R}\{{\bf s}_i\}$ describing the properties of the spins surrounding the central spin ${\bf s}_0$. The Heisenberg star may be considered as an essential structure element of a lattice with frustration (namely a spin embedded in a magnetic matrix $H_R$) or, alternatively, as a magnetic system $H_R$ with a perturbation by an extra spin. We present some general features of the eigenvalues, the eigenfunctions as well as the spin correlation $\langle {\bf s}_0{\bf s}_i \rangle$ of the model. For $H_R$ being a linear chain, a square lattice or a Lieb-Mattis type system we present the ground state properties of the model in dependence on the frustration parameter $\alpha=J_2/J_1$. Furthermore the thermodynamic properties are calculated for $H_R$ being a Lieb--Mattis antiferromagnet.Comment: 16 pages, uuencoded compressed postscript file, accepted to J. Phys. A: Math. Ge

Equation of motion approach to the Hubbard model in infinite dimensions

We consider the Hubbard model on the infinite-dimensional Bethe lattice and construct a systematic series of self-consistent approximations to the one-particle Green's function, $G^{(n)}(\omega),\ n=2,3,\dots\$ . The first $n-1$ equations of motion are exactly fullfilled by $G^{(n)}(\omega)$ and the $n$'th equation of motion is decoupled following a simple set of decoupling rules. $G^{(2)}(\omega)$ corresponds to the Hubbard-III approximation. We present analytic and numerical results for the Mott-Hubbard transition at half filling for $n=2,3,4$.Comment: 10pager, REVTEX, 8-figures not available in postscript, manuscript may be understood without figure

Dzyaloshinskii-Moriya interaction in NaV2_2O5_5: a microscopic study

We present a unified account of magnetic exchange and Raman scattering in the quasi-one-dimensional transition-metal oxide NaV$_2$O$_5$. Based on a cluster-model approach explicit expressions for the exchange integral and the Raman-operator are given. It is demonstrated that a combination of the electronic-structure and the Dzyaloshinskii-Moriya interaction, allowed by symmetry in this material, are responsible for the finite Raman cross-section giving rise to both, one- and two-magnon scattering amplitudes.Comment: 7 pages, 1 figur

Flexible terabit/s Nyquist-WDM super-channels using a gain-switched comb source

Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7\% or 20\% for forward- error correction depending on the individual sub-channel quality after fiber transmission

Modeling the electronic behavior of γ\gamma-LiV2O5: a microscopic study

We determine the electronic structure of the one-dimensional spin-1/2 Heisenberg compound $\gamma$-LiV$_2$O$_5$, which has two inequivalent vanadium ions, V(1) and V(2), via density-functional calculations. We find a relative V(1)-V(2) charge ordering of roughly $70:30$. We discuss the influence of the charge ordering on the electronic structure and the magnetic behavior. We give estimates of the basic hopping matrix elements and compare with the most studied $\alpha '$-NaV$_2$O$_5$.Comment: Final version. To appear in Phys. Rev. Let