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We study the Higgs boson decay into dark matter (DM) in the framework of freeze-in at stronger coupling. Even though the Higgs-DM coupling is significant, up to order one, DM does not thermalize due to the Boltzmann suppression of its production at low temperatures. We find that this mechanism leads to observable Higgs decay into invisible final states with the branching fraction of 10% and below, while producing the correct DM relic abundance. This applies to the DM masses down to the MeV scale, which requires a careful treatment of the hadronic production modes. For DM masses below the muon threshold, the Boltzmann suppression is not operative and the freeze-in nature of the production mechanism is instead guaranteed by the smallness of the electron Yukawa coupling. As a result, MeV DM with a significant coupling to the Higgs boson remains non-thermal as long as the reheating temperature does not exceed $\mathcal{O}(100)\;$MeV. Our findings indicate that there are good prospects for observing light non-thermal DM via invisible Higgs decay at the LHC and FCC., Comment: 23 pages, 9 figures, formulas corrected

Natural language processing (NLP) has seen significant advancements with the advent of large language models (LLMs). However, substantial improvements are still needed for languages other than English, especially for specific domains like the applications of Mercosur Common Nomenclature (NCM), a Brazilian Harmonized System (HS). To address this gap, this study uses TeenyTineLLaMA, a foundational Portuguese LLM, as an LLM source to implement the NCM application processing. Additionally, a simplified Retrieval-Augmented Fine-Tuning (RAFT) technique, termed SLIM-RAFT, is proposed for task-specific fine-tuning of LLMs. This approach retains the chain-of-thought (CoT) methodology for prompt development in a more concise and streamlined manner, utilizing brief and focused documents for training. The proposed model demonstrates an efficient and cost-effective alternative for fine-tuning smaller LLMs, significantly outperforming TeenyTineLLaMA and ChatGPT-4 in the same task. Although the research focuses on NCM applications, the methodology can be easily adapted for HS applications worldwide., Comment: 13 pages, 1 figure, to be publish in International Conference on Web Information Systems and Technologies - WEBIST 2024 proceedings

We use optical-optical double-resonance (OODR) spectroscopy with a continuous wave (CW) pump and a cavity-enhanced frequency comb probe to measure high rotational energy levels of methane in the upper part of the triacontad polyad (P6). A high-power CW optical parametric oscillator, tunable around 3000 cm$^{-1}$, is consecutively locked to the P(7, A$_2$), Q(7, A$_2$), R(7, A$_2$), and Q(6, F$_2$) transitions in the ${\nu}$$_3$ band, and a comb covering the 5800-6100 cm$^{-1}$ range probes sub-Doppler ladder-type transitions from the pumped levels with J' = 6 to 8, respectively. We report 118 probe transitions in the 3${\nu}$$_3$ $\leftarrow$ ${\nu}$$_3$ spectral range with uncertainties down to 300 kHz (1 x 10$^{-5}$ cm$^{-1}$), reaching 84 unique final states in the 9070-9370 cm$^{-1}$ range with rotational quantum numbers J between 5 and 9. We assign these states using combination differences and by comparison to theoretical predictions from a new ab initio-based effective Hamiltonian and dipole moment operator. This is the first line-by-line experimental verification of theoretical predictions for these hot-band transitions, and we find a better agreement of transition wavenumbers with the new calculations compared to the TheoReTS/HITEMP and ExoMol databases. We also compare the relative intensities and find an overall good agreement with all three sets of predictions. Finally, we report the wavenumbers of 27 transitions in the 2${\nu}$$_3$ spectral range, observed as V-type transitions from the ground state, and compare them to the new Hamiltonian, HITRAN2020, ExoMol and the WKMLC line lists.

We propose an active sampling flow, with the use-case of simulating the impact of combined variations on analog circuits. In such a context, given the large number of parameters, it is difficult to fit a surrogate model and to efficiently explore the space of design features. By combining a drastic dimension reduction using sensitivity analysis and Bayesian surrogate modeling, we obtain a flexible active sampling flow. On synthetic and real datasets, this flow outperforms the usual Monte-Carlo sampling which often forms the foundation of design space exploration., Comment: 7 pages

Transition metal dichalcogenide (TMD) monolayers present a singular coupling in their spin and valley degrees of freedom. Moreover, by applying an external magnetic field it is possible to break the energy degeneracy between their K and $-$K valleys. Thus, this analogous valley Zeeman effect opens the possibility of controlling and distinguishing the spin and valley of charge carriers in TMDs by their optical transition energies, making these materials promising for the next generation of spintronic and photonic devices. However, the free excitons of pristine TMD monolayer samples present a moderate valley Zeeman splitting, which is measured by their g-factor values that are approximately $-4$. Therefore, for application purposes it is mandatory alternative excitonic states with higher magnetic responses. Here we investigate the valley Zeeman effect in aged WS$_{2}$ and WSe$_{2}$ grown monolayers by magneto-photoluminescence measurements at cryogenic temperatures. These samples present a lower energy defect-bound exciton emission related to defects adsorbed during the aging process. While the free excitons of these samples exhibit g-factors between $-3$ and $-4$, their defect-bound excitons present giant effective g-factor values of $-(25.0 \pm 0.2)$ and $-(19.1 \pm 0.2)$ for WS$_{2}$ and WSe$_{2}$ aged monolayers, respectively. In addition, we observe a significant spin polarization of charge carriers in the defective mid gap states induced by the external magnetic fields. We explain this spin polarized population in terms of a spin-flip transition mechanism, which is also responsible for the magnetic dependent light emission of the defect-bound exciton states. Our work sheds light in the potential of aged TMDs as candidates for spintronic based devices.

The simplest anisotropic model of the early Universe is the one with two conformal factors, which can be identified as Kantowski-Sachs metric, or the reduced version of the Bianchi-I metric. To fit the existing observational data, it is important that the anisotropy is washed out in the early stage of the evolution. We explore the possible effect of the running cosmological constant (RCC) on the dynamics of isotropy, in the case of the space filled by radiation., Comment: The paper has 16 pages and 16 figures

In this work, we investigate the physical aspects of the inflection-point inflation scenario and assess its observational viability in light of current Cosmic Microwave Background (CMB) data. The model we consider encapsulates the inflaton with a pseudo-scalar (the dark matter candidate) in a complex neutral scalar singlet. The cosmological constraints on the parameters of inflation derived at a high energy scale are translated to a low energy scale by running these parameters. Ensuring the entire Lagrangian to be invariant under a $Z_3$ symmetry with the adequate transformation of the fields, the imaginary part of the singlet decouples from the other scalars of the model. We then investigate if the observational viability of inflation is also compatible with this pseudo-scalar being the dark matter component.We show that the CMB constraints on the inflationary parameters assure that the pseudo-scalar is stable and provides the correct relic dark matter abundance only when the pseudo-scalar is thermally produced., Comment: This manuscript contains 17 pages, 17 figures and 3 tables. Version accepted for publication

Fluidization of solid particles by an ascending fluid is frequent in industry because of the high rates of mass and heat transfers achieved. However, in some cases blockages occur and hinder the correct functioning of the fluidized bed. In this paper, we investigate the crystallization (defluidization) and refluidization that take place in very-narrow solid-liquid fluidized beds under steady flow conditions. For that, we carried out experiments where either monodisperse or bidisperse beds were immersed in water flows whose velocities were above those necessary for fluidization, and the ratio between the tube and grain diameters was smaller than 6. For monodisperse beds consisting of regular spheres, we observed that crystallization and refluidization alternate successively along time, which we quantify in terms of macroscopic structures and agitation of individual grains. We found the characteristic times for crystallization, and propose a new macroscopic parameter quantifying the degree of bed agitation. The bidisperse beds consisted of less-regular spheres placed on the bottom of a layer of regular spheres (the latter was identical to the monodisperse beds tested). We measured the changes that macroscopic structures and agitation of grains undergo, and show that the higher agitation in the bottom layer hinders crystallization of the top layer. Our results bring new insights into the dynamics of very-narrow beds, in addition to proposing a way of mitigating defluidization.

Accurate parameters of molecular hot-band transitions, i.e., those starting from vibrationally excited levels, are needed to accurately model high-temperature spectra in astrophysics and combustion, yet laboratory spectra measured at high temperatures are often unresolved and difficult to assign. Optical-optical double-resonance (OODR) spectroscopy allows the measurement and assignment of individual hot-band transitions from selectively pumped energy levels without the need to heat the sample. However, previous demonstrations lacked either sufficient resolution, spectral coverage, absorption sensitivity, or frequency accuracy. Here we demonstrate OODR spectroscopy using a cavity-enhanced frequency comb probe that combines all these advantages. We detect and assign sub-Doppler transitions in the spectral range of the 3${\nu}$${_3}$${\leftarrow}$${\nu}$${_3}$ resonance of methane with frequency precision and sensitivity more than an order of magnitude better than before. This technique will provide high-accuracy data about excited states of a wide range of molecules that is urgently needed for theoretical modeling of high-temperature data and cannot be obtained using other methods., Comment: Addendum added on Aug 20, 2024, containing comparison of experimental line positions and intensities to new predictions from an effective Hamiltonian and the ExoMol database

We study a simple extension of the Standard Model featuring a dark sector with an ultralight pseudo Nambu-Goldstone boson as dark matter candidate. We focus on the mass range $\mathcal{O}(10^{-20} - 10^{-10})$ eV, relevant for strong gravity applications, and explore its production and evolution in the early Universe. The model is formulated in such a way that dark matter does not couple directly to photons or other Standard Model particles avoiding some of the most stringent cosmological bounds related to axion-like particles. In this work, two different scenarios are considered depending on whether dark matter is produced in a pre-inflationary or post-inflationary regime. We also discuss the effect from emergent topological defects such as cosmic strings and domain walls, and estimate the spectrum of stochastic gravitational waves produced by their decay, enabling to test the model at current and future gravitational-wave experiments., Comment: 22 pages, 5 figures

Meson and anti-meson mixing processes constitute an important source of constraints on models that give tree level contributions to flavor violating neutral processes. In electroweak $ \text{SU}(3)_\text{L} \times \text{U}(1)_N $ models, where anomaly cancellation requires that one family of quarks transforms differently from the other ones, processes involving flavor changing neutral currents gain tree level contributions mediated by gauge and scalar fields. Here, we firstly investigate the contributions of the neutral scalar that mimics the standard Higgs to the $K^0-\bar K^0$, $B^0-\bar B^0$, and $D^0-\bar D^0$ mixing processes and confront our predictions with experiments. The results will determine the quark mixing matrices $V^{u,d}_L$. In possession of this information we, next, evaluate the contributions of the neutral gauge bosons $Z^{\prime}$ and $Z$ to the $K^0-\bar K^0$, $B^0-\bar B^0$, and $D^0-\bar D^0$ processes. This realistic approach to meson transitions will provide severe bounds on $M_{ Z^{\prime}}$ and $Z-Z^{\prime}$ mixing angle., Comment: Typos fixed, references added, 19 pages, 3 figures. Matches published version

In 3-3-1 models anomaly cancellation requires that one of the three families of quarks transforms as triplet by $\text{SU}(3)_\text{L}$ with the other two transforming necessarily as anti-triplet. This is an important feature of the model because with it we explain family replication. Thus it is mandatory to discriminate which of the families will transform as triplet by $\text{SU}(3)_\text{L}$ because the main consequence of anomaly cancellation in 3-3-1 models is the arising of processes violating flavor at tree level by means of neutral currents mediated by gauge and scalar fields and each case leads to different results. In this work we consider the 3-3-1 model with right-handed neutrinos. Among the spectrum of 3-3-1 particles that contributes to the flavor changing neutral processes, there is a pseudoscalar that may be the lightest of the 3-3-1 particles and then should give the main contribution to such processes. We then calculate its contribution to the $K^0 -\bar K^0$ mixing transition and confront it with the current experimental results. We do this for the three cases in which one of the family of quarks transforms as a triplet by $\text{SU}(3)_\text{L}$. According to our findings each case leads to different constraints on the mass of the pseudoscalar and the case in which the third family of quarks transforms as triplet seems to be the favoured one. We also obtain the most stringent bounds on the mass of the pseudoscalar of the model., Comment: Typos fixed, references added, conclusions unchanged, 17 pages, 1 figures. Matches published version

We report the broadband absorption spectrum of the $3\nu_{2}$ band of $^{14}$NH$_{3}$ near 4 $\mu m$. The data were recorded using a mid-infrared frequency comb coupled to a homebuilt Fourier-transform spectrometer with a resolution of 0.00501 $cm^{-1}$. Line positions, line intensities, self-broadening, and self-shift parameters for six rovibrational lines were determined at room temperature ($T=296$ K). Comparison with HITRAN 2016 shows good agreement at improved precision. The high precision and the rapid tunability of our experiment enables advanced fast spectroscopy of molecular gases.

The framework of the so-called 3-3-1LHN model may accommodate two different, but viable, scenarios of dark matter: one involving a heavy Dirac neutrino , $N_1$, or another having a scalar, $\phi$, as dark matter candidate. In both cases the dark matter phenomenology, relic abundance and scattering cross section off of nuclei, is controlled by exchange of $Z^{\prime}$. We then investigate the impact on the parameter space $(M_{Z^{\prime}}\,,\,M_{(N_1\,,\, \phi)})$ due to the recent Pandax-4T experimental result in both scenarios. First, the Pandax-4T experiment excludes scenarios with dark matter mass below $1.9$ TeV. Concerning $Z^{\prime}$, we find the lower bound $M_{Z^{\prime}}> 4.1$ TeV for the case when $N_1$ as the dark matter and $ M_{Z^{\prime}}>5.7$ TeV for the other case. This implies that the 3-3-1 symmetry is spontaneously broken above $10$ TeV scale. We also comment on the contributions to the relic abundance of processes involving flavor changing neutral current mediated by $Z^{\prime}$., Comment: 15 pages, 8 figures, Matches version accepted in Phys. Rev. D