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Quasiparticles are central to condensed matter physics, but their stability can be undermined by quantum many-body interactions. Magnons, quasiparticles in quantum magnets, are particularly intriguing because their properties are governed by both real and spin space. While crystal symmetries may be low, spin interactions often remain approximately isotropic, limiting spontaneous magnon decay. Textbook wisdom holds that collinear Heisenberg magnets follow a dichotomy: ferromagnets host stable magnons, while antiferromagnetic magnons may decay depending on dispersion curvature. Up to now, relativistic spin-orbit coupling and noncollinear order that connect spin space to real space, were shown to introduce more complex magnon instability mechanisms. Here, we show that even in nonrelativistic isotropic collinear systems, this conventional dichotomy is disrupted in altermagnets. Altermagnets, a newly identified class of collinear magnets, exhibit compensated spin order with nonrelativistic time-reversal symmetry breaking and even-parity band splitting. Using kinematic analysis, nonlinear spin-wave theory, and quantum simulations, we reveal that even weak band splitting opens a decay phase space, driving quasiparticle breakdown. Additionally, d-wave altermagnets form a rare ``island of stability'' at the Brillouin zone center. Our findings establish a quasiparticle stability trichotomy in collinear Heisenberg magnets and position altermagnets as a promising platform for unconventional spin dynamics., Comment: 14 pages

RuCl$_3$ was likely the first ever deliberately synthesized ruthenium compound, following the discovery of the $_{44}$Ru element in 1844. For a long time it was known as an oxidation catalyst, with its physical properties being discrepant and confusing, until a decade ago when its allotropic form $\alpha$-RuCl$_3$ rose to exceptional prominence. This "re-discovery" of $\alpha$-RuCl$_3$ has not only reshaped the hunt for a material manifestation of the Kitaev spin liquid, but it has opened the floodgates of theoretical and experimental research in the many unusual phases and excitations that the anisotropic-exchange magnets as a class of compounds have to offer. Given its importance for the field of Kitaev materials, it is astonishing that the low-energy spin model that describes this compound and its possible proximity to the much-desired spin-liquid state is still a subject of significant debate ten years later. In the present study, we argue that the existing key phenomenological observations put strong natural constraints on the effective microscopic spin model of $\alpha$-RuCl$_3$, and specifically on its spin-orbit-induced anisotropic-exchange parameters that are responsible for the non-trivial physical properties of this material. These constraints allow one to focus on the relevant region of the multi-dimensional phase diagram of the $\alpha$-RuCl$_3$ model, suggest an intuitive description of it via a different parametrization of the exchange matrix, offer a unifying view on the earlier assessments of its parameters, and bring closer together several approaches to the derivation of anisotropic-exchange models. We explore extended phase diagrams relevant to the $\alpha$-RuCl$_3$ parameter space using quasi-classical, Luttinger-Tisza, exact diagonalization, and density-matrix renormalization group methods, demonstrating a remarkably c... (arxiv cutoff; for the rest, see the paper), Comment: 39 pages, 28 Figures. Text of immense pedagogical power. Fixed Ref. [1]

Quantum computing has long been an experimental technology with the potential to simulate, at scale, phenomena which on classical devices would be too expensive to simulate at any but the smallest scales. Over the last several years, however, it has entered the NISQ era, where the number of qubits are sufficient for quantum advantage but substantial noise on hardware stands in the way of this achievement. This thesis details NISQ device-centered improvements to techniques of quantum simulation of the out-of-equilbrium real-time dynamics of lattice quantum chromodynamics (LQCD) and of dense 3-flavor neutrino systems on digital quantum devices. The first project concerning LQCD is a comparison of methods for implementing the variational quantum eigensolver (VQE) that initializes the ground state of an SU(3) plaquette-chain. The thesis then pivots to a 1+1D lattice of quarks interacting with an SU(3) gauge-field. A VQE-based state-preparation for the vacua and a Trotterized time-evolution circuit is designed and applied to the problems of simulating beta and neutrinoless double beta decay. Finally, these circuits are adapted to a version useable on quantum devices with nearest-neighbor connectivity with minimal overhead, with an eye towards utilizing the higher qubit count of such devices for hadron dynamics and scattering. This thesis covers two projects that concern dense 3-flavor neutrino systems. The first details design and testing of Trotterized time-evolution circuits on state-of-the-art quantum devices. The second, motivated by the Gottesman-Knill theorem's result that deviation from stabilizer states ("magic") is necessary for a problem to exhibit quantum advantage, details results with implications for the Standard Model in general that the 3 flavor ultradense neutrino systems with the highest, most-persistent magic are those that start with neutrinos in all 3 flavors., Comment: Ph.D. thesis; 362 pages, 106 figures, 41 tables

Rapid advancements of large language model (LLM) technologies led to the introduction of powerful open-source instruction-tuned LLMs that have the same text generation quality as the state-of-the-art counterparts such as GPT-4. While the emergence of such models accelerates the adoption of LLM technologies in sensitive-information environments the authors of such models don not disclose the training data necessary for replication of the results thus making the achievements model-exclusive. Since those open-source models are also multilingual this in turn reduces the benefits of training a language specific LLMs as improved inference computation efficiency becomes the only guaranteed advantage of such costly procedure. More cost-efficient options such as vocabulary extension and subsequent continued pre-training are also inhibited by the lack of access to high-quality instruction-tuning data since it is the major factor behind the resulting LLM task-solving capabilities. To address the limitations and cut the costs of the language adaptation pipeline we propose Learned Embedding Propagation (LEP). Unlike existing approaches our method has lower training data size requirements due to minimal impact on existing LLM knowledge which we reinforce using novel ad-hoc embedding propagation procedure that allows to skip the instruction-tuning step and instead implant the new language knowledge directly into any existing instruct-tuned variant. We evaluated four Russian vocabulary adaptations for LLaMa-3-8B and Mistral-7B, showing that LEP is competitive with traditional instruction-tuning methods, achieving performance comparable to OpenChat 3.5 and LLaMa-3-8B-Instruct, with further improvements via self-calibration and continued tuning enhancing task-solving capabilities., Comment: Preprint version of an article published in the Journal of Language and Education. Copyright held by the owner/author(s). Publication rights licensed to the Journal of Language and Education

The phase diagram of the $S\!=\!1/2$ easy-axis triangular-lattice $J_1\!-\!J_2$ model is investigated using the density-matrix renormalization group and analytical insights. We find a significant spin-liquid region extending from the Heisenberg limit and residing between the Y phase-known as the magnetic analogue of the "supersolid"-and collinear stripe phase. The order parameters of the supersolid are analyzed and an understanding of its lack of ferromagnetic moment is suggested., Comment: 5 pages main text, 2+8 pages supplemental material

The current evaluation of mathematical skills in LLMs is limited, as existing benchmarks are either relatively small, primarily focus on elementary and high-school problems, or lack diversity in topics. Additionally, the inclusion of visual elements in tasks remains largely under-explored. To address these gaps, we introduce U-MATH, a novel benchmark of 1,100 unpublished open-ended university-level problems sourced from teaching materials. It is balanced across six core subjects, with 20% of multimodal problems. Given the open-ended nature of U-MATH problems, we employ an LLM to judge the correctness of generated solutions. To this end, we release $\mu$-MATH, a dataset to evaluate the LLMs' capabilities in judging solutions. The evaluation of general domain, math-specific, and multimodal LLMs highlights the challenges presented by U-MATH. Our findings reveal that LLMs achieve a maximum accuracy of only 63% on text-based tasks, with even lower 45% on visual problems. The solution assessment proves challenging for LLMs, with the best LLM judge having an F1-score of 80% on $\mu$-MATH.

The paper presents the results of a theoretical study of the noise shielding effect of a subsonic turbulent jet located near a rigid screen. The developed theoretical model, based on the methods of the Geometrical Theory of Diffraction (GTD), takes into account the effects of scattering of the hydrodynamic fluctuations of the jet near field at the edges of the screen and diffraction of acoustic perturbations generated by small-scale turbulence. Small-scale turbulent noise radiating pulsations are described within the framework of the correlation theory of jet noise in the form of compact quadrupole sources distributed along the jet axis. Hydrodynamic near-field fluctuations are approximated as a superposition of Kelvin-Helmholtz instability wave packets of different azimuthal numbers. Typical parameters of both types of fluctuations are adjusted using experimental data on the near and far fields of a free jet issuing from a profiled nozzle with a diameter of 0.04 m at a velocity of 181 m/s. The result of the jet noise shielding efficiency calculation, using the developed model, is in good agreement with the experimental data obtained for the jet-plate configuration, including correct reproduction of the low-frequency noise amplification (jet-plate installation noise) and the effect of high-frequency noise decrease (shielding itself)., Comment: 19 pages, 10 figures

Training and deploying machine learning models relies on a large amount of human-annotated data. As human labeling becomes increasingly expensive and time-consuming, recent research has developed multiple strategies to speed up annotation and reduce costs and human workload: generating synthetic training data, active learning, and hybrid labeling. This tutorial is oriented toward practical applications: we will present the basics of each strategy, highlight their benefits and limitations, and discuss in detail real-life case studies. Additionally, we will walk through best practices for managing human annotators and controlling the quality of the final dataset. The tutorial includes a hands-on workshop, where attendees will be guided in implementing a hybrid annotation setup. This tutorial is designed for NLP practitioners from both research and industry backgrounds who are involved in or interested in optimizing data labeling projects., Comment: To be presented at COLING 2025

We consider the quantum magic in systems of dense neutrinos undergoing coherent flavor transformations, relevant for supernova and neutron-star binary mergers. Mapping the three-flavor-neutrino system to qutrits, the evolution of quantum magic is explored in the single scattering angle limit for a selection of initial tensor-product pure states for $N_\nu \le 8$ neutrinos. For $|\nu_e\rangle^{\otimes N_\nu}$ initial states, the magic, as measured by the $\alpha=2$ stabilizer Renyi entropy $M_2$, is found to decrease with radial distance from the neutrino sphere, reaching a value that lies below the maximum for tensor-product qutrit states. Further, the asymptotic magic per neutrino, $M_2/N_\nu$, decreases with increasing $N_\nu$. In contrast, the magic evolving from states containing all three flavors reaches values only possible with entanglement, with the asymptotic $M_2/N_\nu$ increasing with $N_\nu$. These results highlight the connection between the complexity in simulating quantum physical systems and the parameters of the Standard Model., Comment: 15 pages, 8 figures

Rare-earth orthoferrites are a promising platform for antiferromagnetic spintronics with a rich variety of terahertz spin and lattice dynamics phenomena. For instance, it has been experimentally demonstrated that the light-driven optical phonons can coherently manipulate macroscopic magnetic states via nonlinear magnetophononic effects. Here using TbFeO$_{3}$ as an example, we reveal the origin of the mode mixing between the LO and TO phonons, which is important for understanding of nonlinear phononics. We performed a comprehensive study of the lattice dynamics of the TbFeO$_{3}$ single crystal by polarized infrared and Raman scattering spectroscopic techniques, and experimentally obtained and carefully analyzed the spectra of anisotropic complex dielectric functions in the far-infrared spectral range. This allowed us to reliably identify the symmetries and parameters of most infrared- and Raman-active phonons. Next, the experimental studies were supplemented by the lattice dynamics calculations which allowed us to propose the normal mode assignments. We reveal that the relation between LO and TO polar phonons is complex and does not strictly follow the ``LO-TO rule'' due to the strong mode mixing. We further analyze how displacements of different ions contribute to phonon modes and reveal that magnetic Fe ions are not involved in Raman-active phonons, thus shedding light on a lack of spin phonon coupling for such phonons. The obtained results establish a solid basis for further in-depth experimental research in the field of nonlinear phononics and magnetophononics in rare-earth orthoferrites., Comment: 23 pages, 15 figures, 6 tables

The hadroproduction of single isolated photon at high energies is studied within the framework of the NLO${}^\star$ approximation of the Parton Reggeization Approach based on the modified Multi-Regge limit of the hard scattering QCD amplitudes. The contribution from the LO subprocess $Q \bar Q \to \gamma$ and the NLO tree-level corrections $Q R \to \gamma q$ and $Q \bar Q \to \gamma g$ are considered. To avoid specific double counting in rapidity between tree-level corrections to the hard scattering coefficient and unintegrated PDFs, a corresponding subtraction scheme is proposed. We demonstrated self-consistency of the Parton Reggeization Approach using the subtraction scheme. The results of calculations are compared with data from various Collaborations in the wide energy range $\sqrt{S} = 24 \ {\rm GeV} - 13 \ {\rm TeV}$. We obtained a quite satisfactory agreement with data up to $p_T^\gamma / \sqrt{S} \simeq 0.2 - 0.3$. Predictions for the future SPD NICA experiment were discussed., Comment: 27 pages, 12 figures, 1 Table

We propose the conjecture that every graph $G$ of order $n$ with less than $3n-6$ edges has a vertex cut that induces a forest. Maximal planar graphs do not have such vertex cuts and show that the density condition would be best possible. We verify the conjecture for planar graphs and show that every graph $G$ of order $n$ with less than $\frac{11}{5}n-\frac{18}{5}$ edges has a vertex cut that induces a forest.

In the article, we study pair production of $\psi[1S]$ and $\psi[2S]$ charmonium states in the forward rapidity region of the LHCb experiment at the $\sqrt{s} = 13$ TeV using the improved color evaporation model and the parton Reggeization approach, which is a gauge invariant version of the $k_T$-factorization approach. Taking into account single and double parton scattering mechanisms and using the set of model parameters which have been fixed early, we compare our theoretical predictions with the recent LHCb experimental data as well as with another theoretical predictions. The numerical calculations are performed using the parton--level Monte-Carlo event generator KaTie and modified KMRW model for unintegrated parton distribution functions. We have found absolutely dominant role of the double parton scattering mechanism in the charmonium pair production at the LHCb., Comment: 12 pages, 3 figures, 1 table

In the article, we study the processes of single isolated photon production at the LHC energies in the framework of the Parton Reggeization Approach taking into account LO and NLO* contributions, the last one includes only tree-level corrections. Reggeized amplitudes are constructed according to the effective field theory formalism for multi-Regge kinematics processes suggested by L.N. Lipatov. To avoid the double counting between tree-level corrections and unintegrated parton distribution functions, a subtraction scheme is introduced. The results of calculations are compared with experimental data., Comment: 8 pages, 3 figures, Talk at the Hadron Structure and Fundamental Interactions: from Low to High Energies, Gatchina, Russia, July 8 - 12, 2024

We explore the utility of qutrits and qubits for simulating the flavor dynamics of dense neutrino systems. The evolution of such systems impacts some important astrophysical processes, such as core-collapse supernovae and the nucleosynthesis of heavy nuclei. Many-body simulations require classical resources beyond current computing capabilities for physically relevant system sizes. Quantum computers are therefore a promising candidate to efficiently simulate the many-body dynamics of collective neutrino oscillations. Previous quantum simulation efforts have primarily focused on properties of the two-flavor approximation due to their direct mapping to qubits. Here, we present new quantum circuits for simulating three-flavor neutrino systems on qutrit- and qubit-based platforms, and demonstrate their feasibility by simulating systems of two, four and eight neutrinos on IBM and Quantinuum quantum computers., Comment: 19 pages, 4 tables, 15 figures

In this paper, we propose a fast method for crack detection in 3D computed tomography (CT) images. Our approach combines the Maximal Hessian Entry filter and a Deep-First Search algorithm-based technique to strike a balance between computational complexity and accuracy. Experimental results demonstrate the effectiveness of our approach in detecting the crack structure with predefined misclassification probability.

Learned video compression methods already outperform VVC in the low-delay (LD) case, but the random-access (RA) scenario remains challenging. Most works on learned RA video compression either use HEVC as an anchor or compare it to VVC in specific test conditions, using RGB-PSNR metric instead of Y-PSNR and avoiding comprehensive evaluation. Here, we present an end-to-end learned video codec for random access that combines training on long sequences of frames, rate allocation designed for hierarchical coding and content adaptation on inference. We show that under common test conditions (JVET-CTC), it achieves results comparable to VTM (VVC reference software) in terms of YUV-PSNR BD-Rate on some classes of videos, and outperforms it on almost all test sets in terms of VMAF BD-Rate. On average it surpasses open LD and RA end-to-end solutions in terms of VMAF and YUV BD-Rates.

In extreme environments such as core-collapse supernovae, neutron-star mergers, and the early Universe, neutrinos are dense enough that their self-interactions significantly affect, if not dominate, their flavor dynamics. In order to develop techniques for characterizing the resulting quantum entanglement, I present the results of simulations of Dirac neutrino-neutrino interactions that include all three physical neutrino flavors and were performed on D-Wave Inc.'s {\tt Advantage} 5000+ qubit quantum annealer. These results are checked against those from exact classical simulations, which are also used to compare the Dirac neutrino-neutrino interactions to neutrino-antineutrino and Majorana neutrino-neutrino interactions. The D-Wave {\tt Advantage} annealer is shown to be able to reproduce time evolution with the precision of a classical machine for small numbers of neutrinos and to do so without Trotter errors. However, it suffers from poor scaling in qubit-count with the number of neutrinos., Comment: 31 pages, 7 figures, 4 tables

We study the $k$-Canadian Traveller Problem, where a weighted graph $G=(V,E,\omega)$ with a source $s\in V$ and a target $t\in V$ are given. This problem also has a hidden input $E_* \subsetneq E$ of cardinality at most $k$ representing blocked edges. The objective is to travel from $s$ to $t$ with the minimum distance. At the beginning of the walk, the blockages $E_*$ are unknown: the traveller discovers that an edge is blocked when visiting one of its endpoints. Online algorithms, also called strategies, have been proposed for this problem and assessed with the competitive ratio, {\em i.e.}, the ratio between the distance actually traversed by the traveller divided by the distance he would have traversed knowing the blockages in advance. Even though the optimal competitive ratio is $2k+1$ even on unit-weighted planar graphs of treewidth 2, we design a polynomial-time strategy achieving competitive ratio 9 on unit-weighted outerplanar graphs. This value 9 also stands as a lower bound for this family of graphs as we prove that, for any $\varepsilon > 0$, no strategy can achieve a competitive ratio $9-\varepsilon$ on it. This comes actually from a strong connexion with another well-known online problem called the cow-path problem. Finally, we show that it is not possible to achieve a competitive ratio $e^{W(\frac{\ln k}{2})} - 1$ on arbitrarily weighted outerplanar graphs, where $W$ is the Lambert W function. This lower bound is asymptotically greater than $\frac{\ln k}{\ln \ln k}$.

In the article, we study associated production of prompt $J/\psi(\Upsilon)$ and $D-$mesons in the improved color evaporation model using the high-energy factorization approach as it is realized in the Monte-Carlo event generator KaTie. The modified Kimber-Martin-Ryskin-Watt model for unintegrated parton distribution functions is used. We predict cross sections for associated $J/\psi(\Upsilon)$ and $D-$meson hadroproduction via the single and double parton scattering mechanisms using the set of model parameters which has been fixed early for description of prompt single and pair heavy quarkonium production at the LHC energies. We found the results of calculations agree with the LHCb Collaboration data at the energies $\sqrt{s} = 7,8$ TeV and we present theoretical predictions for the energy $\sqrt{s} = 13$ TeV ., Comment: 16 pages, 8 figures, 1 table

In this article we continue to study the concept of entropy introduced in [4], [15]-[17]. We calculate entropy for a wider class of finite-dimensional operators in comparison with [15]. We also approximate the entropy of a unitary operator on $l^2(\mathbb{N}_0)$ by the entropy of finite-dimensional operators. Finally we calculate the entropy of several operators on $l^2(\mathbb{N}_0)$.

In this work, we study effects of magnon interactions in the excitation spectrum of CoNb$_2$O$_6$ in the quantum paramagnetic phase in transverse field, where the $1/S$ spin-wave theory exhibits unphysical divergences at the critical field. We propose a self-consistent Hartree-Fock approach that eliminates such unphysical singularities while preserving the integrity of the singular threshold phenomena of magnon decay and spectrum renormalization that are present in both theory and experiment. With the microscopic parameters adopted from previous studies, this method yields a close quantitative agreement with the available experimental data for CoNb$_2$O$_6$ in the relevant regime. Insights into the general structure of the spin-anisotropic model of CoNb$_2$O$_6$ and related zigzag chain materials are also provided and a discussion of the effects of additional longitudinal field on the spectrum is given., Comment: 27 pages, 18 figures, must-read appendices; recipient of the PRB beauty Award

Latest instruction-tuned large language models (LLM) show great results on various tasks, however, they often face performance degradation for non-English input. There is evidence that the reason lies in inefficient tokenization caused by low language representation in pre-training data which hinders the comprehension of non-English instructions, limiting the potential of target language instruction-tuning. In this work we investigate the possibility of addressing the issue with vocabulary substitution in the context of LLaMa Russian language adaptation. We explore three variants of vocabulary adaptation and test their performance on Saiga instruction-tuning and fine-tuning on Russian Super Glue benchmark. The results of automatic evaluation show that vocabulary substitution not only improves the model's quality in Russian but also accelerates fine-tuning (35%) and inference (up to 60%) while reducing memory consumption. Additional human evaluation of the instruction-tuned models demonstrates that models with Russian-adapted vocabulary generate answers with higher user preference than the original Saiga-LLaMa model.

The extraordinary properties of the Kitaev model have motivated an intense search for new physics in materials that combine geometrical and bond frustration. In this work, we employ inelastic neutron scattering, spin wave theory, and exact diagonalization to study the spin dynamics in the perfect triangular-lattice antiferromagnet (TLAF) CsCeSe$_2$. This material orders into a stripe phase, which is demonstrated to arise as a consequence of the off-diagonal bond-dependent terms in the spin Hamiltonian. By studying the spin dynamics at intermediate fields, we identify an interaction between the single-magnon state and the two-magnon continuum that causes decay of coherent magnon excitations, level repulsion, and transfer of spectral weight to the continuum that are controlled by the strength of the magnetic field. Our results provide a microscopic mechanism for the stabilization of the stripe phase in TLAF and show how complex many-body physics can be present in the spin dynamics in a magnet with strong Kitaev coupling even in an ordered ground state., Comment: 6 + 10 pages, 4 + 11 figures

The two-dimensional triangular-lattice antiferromagnet (TLAF) is a textbook example of frustrated magnetic systems. Despite its simplicity, the TLAF model exhibits a highly rich and complex magnetic phase diagram, featuring numerous distinct ground states that can be stabilized through frustrated next-nearest-neighbor couplings or anisotropy. In this paper, we report low-temperature magnetic properties of the TLAF material CsCeSe$_2$. The inelastic neutron scattering (INS) together with specific heat measurements and density functional theory calculations of crystalline electric field suggest that the ground state of Ce ions is a Kramers doublet with strong easy-plane anisotropy. Elastic neutron scattering measurements demonstrate the presence of stripe-$yz$ magnetic order that develops below $T_{\rm N} = 0.35$ K, with the zero-field ordered moment of $m_{\rm Ce} \approx 0.65~\mu_{\rm B}$. Application of magnetic field first increases the ordering temperature by about 20% at the intermediate field region and eventually suppresses the stripe order in favor of the field-polarized ferromagnetic state via a continuous quantum phase transition (QPT). The field-induced response demonstrates sizable anisotropy for different in-plane directions, $\mathbf{B}\parallel{}\mathbf{a}$ and $\mathbf{B}\perp{}\mathbf{a}$, which indicates the presence of bond-dependent coupling in the spin Hamiltonian. We further show theoretically that the presence of anisotropic bond-dependent interactions can change the universality class of QPT for $\mathbf{B}\parallel{}\mathbf{a}$ and $\mathbf{B}\perp{}\mathbf{a}$., Comment: 15 pages, 8 figures