Background Field Research Articles

Scrutinizing B0-meson flavor changing neutral current decay into scalar K0∗(1430) meson with b→sℓ+ℓ-(νν¯) transition

In this paper, we investigate the rare decay B0→K0∗(1430)ℓ+ℓ- with ℓ=(e,μ,τ) and B0→K0∗(1430)νν¯ induced by the flavor changing neutral current transition of b→sℓ+ℓ-(νν¯). Firstly, the B0→K0∗(1430) transition form factors (TFFs) are calculated by using the QCD light-cone sum rule approach up to next-to-leading order accuracy. In which the K0∗(1430)-meson twist-2 and twist-3 LCDAs have been calculated both from the SVZ sum rule in the background field theory framework and light-cone harmonic oscillator model. Then, we obtain the three TFFs at large recoil point, i.e., f+B0→K0∗(0)=0.470-0.101+0.086, f-B0→K0∗(0)=-0.340-0.068+0.068, and fTB0→K0∗(0)=0.537-0.115+0.112. Meanwhile, we extrapolate TFFs to the whole physical q2-region by using the simplified z(q2)-series expansion. Furthermore, we calculate the B0→K0∗(1430)ℓ+ℓ-(νν¯) decay widths, branching fractions, and longitudinal lepton polarization asymmetries of B0→K0∗(1430)ℓ+ℓ-, which lead to B(B0→K0∗(1430)e+e-)=(6.65-2.42+2.52)×10-7, B(B0→K0∗(1430)μ+μ-)=(6.62-2.41+2.51)×10-7, B(B0→K0∗(1430)τ+τ-)=(1.88-0.97+1.10)×10-8, B(B0→K0∗(1430)νν¯)=3.85-1.48+1.55×10-6 and the integrated longitudinal lepton polarization asymmetries ⟨APL⟩=(-0.99,-0.96,-0.03) for the cases ℓ=(e,μ,τ) respectively.

Impact of Anticyclonic Mesoscale Eddies on the Vertical Structures of Marine Heatwaves in the South China Sea

Under global warming, the South China Sea (SCS) is experiencing increasingly severe marine heatwaves (MHWs), with impacts on marine ecosystems such as coral reefs and marine pastures becoming more evident. The numerous anticyclonic eddies (AEs) distributed in the SCS are important drivers of MHW generation and development, yet their impacts on MHWs are still not fully understood. In this study, the vertical structures of various types of MHWs inside the AEs and in the background field were mapped and compared, and we found that AEs of varying amplitudes have distinct impacts on the vertical structures of MHWs. MHWs inside the AEs can be divided into two categories: subsurface-reversed MHWs and subsurface-intensified MHWs. The former is manifested as anomalous cooling in the subsurface, driven by the uplift of thermocline due to the inhibition of downward mixing. The latter is characterized by anomalous warming in the subsurface, resulting from strong vertical warm-water subsidence induced by large-amplitude AEs. This process may penetrate the thermocline and produce maximum warming anomalies in the layer beneath the region of greatest temperature gradient change. Our research reveals characteristics of various vertical structures of MHWs in the SCS, attributing their differences to the stable water layer’s different response to varying intensities of vertical heat conduction, and deepening people’s understanding of the impact of AEs in the SCS on the vertical structure of MHWs.

Book Review: “Background Independence in Classical and Quantum Gravity” by James Read

Book Review: “Background Independence in Classical and Quantum Gravity” by James Read

Impact of background field localization on vacuum polarization effects

Impact of background field localization on vacuum polarization effects

Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM

Abstract A recent report on the detection of very-high-energy gamma rays from V4641 Sagittarii (V4641 Sgr) up to ≈0.8 PeV has made it the second confirmed “PeVatron” microquasar. Here we report on the observation of V4641 Sgr with X-Ray Imaging and Spectroscopy Mission (XRISM) in 2024 September. Thanks to the large field of view and low background, the CCD imager Xtend successfully detected for the first time X-ray extended emission around V4641 Sgr with a significance of ≳4.5σ and >10σ based on our imaging and spectral analysis, respectively. The spatial extent is estimated to have a radius of 7′ ± 3′ (13 ± 5 pc at a distance of 6.2 kpc) assuming a Gaussian-like radial distribution, which suggests that the particle acceleration site is within ~10 pc of the microquasar. If the X-ray morphology traces the diffusion of accelerated electrons, this spatial extent can be explained by either an enhanced magnetic field (∼80 μG) or a suppressed diffusion coefficient (∼1027 cm2 s−1 at 100 TeV). The integrated X-ray flux, (4–6) × 10−12 erg s−1 cm−2 (2–10 keV), would require a magnetic field strength higher than the Galactic mean (≳8 μG) if the diffuse X-ray emission originates from synchrotron radiation and the gamma-ray emission is predominantly hadronic. If the X-rays are of thermal origin, the measured extension, temperature, and plasma density can be explained by a jet with a luminosity of ∼2 × 1039 erg s−1, which is comparable to the Eddington luminosity of this system.

Finite-temperature instantons from first principles

We derive the finite-temperature quantum-tunneling rate from first principles. The tunneling rate depends on both temperature and time. We demonstrate that the relevant instantons should, therefore, be defined on a Keldysh-Schwinger contour, and we discuss how the familiar Euclidean time result arises from the limit of large physical times. We identify distinct behavior in the high- and low-temperature limits, incorporating effects from background fields. We construct a consistent perturbative scheme that incorporates large finite-temperature effects. Published by the American Physical Society 2024

Probing |Vcs| and lepton flavor universality through D→K0*(1430)ℓνℓ decays

In this paper, we calculate the semileptonic decays D→K0*(1430)ℓνℓ with ℓ=(e,μ) induced by c→sℓνℓ transition. For the key component, D→K0*(1430) transition form factors (TFFs) f±(q2) are calculated within the framework of QCD light cone sum rule. Then, we consider two scenarios for K0*(1430)-meson twist-2 distribution amplitude. For the scenario 1 (S1), we take the truncated form based on Gegenbauer polynomial series. Meanwhile, we also consider the scenario 2 (S2) constructed by light cone harmonic oscillator model, where the model parameters are fixed by the K0*(1430)-meson twist-2 distribution amplitude tenth-order ξ moments calculated by using the background field theory. For the TFFs at a large recoil point, we have f+(S1)(0)=0.597−0.121+0.122 and f−(S1)(0)=−0.136−0.035+0.023, f+(S2)(0)=0.663−0.134+0.135, and f−(S2)(0)=−0.202−0.046+0.026. After extrapolating TFFs to the whole physical q2 region, we calculate the branching fractions of D0→K0*+(1430)ℓ−ν¯ℓ and D+→K0*0(1430)ℓ+νℓ, which at 10−4-order level for the S1 and S2 cases. Meanwhile, we predict the CKM matrix |Vcs|(S1)=0.973−0.183+0.259, |Vcs|(S2)=0.880−0.165+0.234, and lepton flavor universality RK0*(S1)=0.768−0.368+0.560, RK0*(S2)=0.764−0.365+0.555. Finally, we discuss the angular observables of forward-backward asymmetries, lepton polarization asymmetries, and q2-differential flat terms for this decay. Published by the American Physical Society 2024

SOFIA/HAWC+ Far-infrared Polarimetric Large-area CMZ Exploration Survey. IV. Relative Magnetic Field Orientation throughout the CMZ

Abstract The nature of the magnetic field structure throughout the Galactic Center (GC) has long been of interest. The recent Far-InfraREd Polarimetric Large-Area Central Molecular Zone (CMZ) Exploration (FIREPLACE) Survey reveals preliminary connections between the seemingly distinct vertical and horizontal magnetic field distributions previously observed in the GC. We use the statistical techniques of the Histogram of Relative Orientation and the Projected Rayleigh Statistic to assess whether the CMZ magnetic field preferentially aligns with the structure of the CMZ molecular clouds or the morphology of the nonthermal emission of the GC nonthermal filament (NTF) population. We find that there is a range of magnetic field orientations throughout the population of CMZ molecular clouds, ranging from parallel to perpendicular orientation. We posit these orientations depend on the prevalence of gravitational shear in the GC, in contrast with what is observed in Galactic Disk star-forming regions. We also compare the magnetic field orientation from dust polarimetry with individual prominent NTFs, finding a preferred perpendicular relative orientation. This perpendicular orientation indicates that the vertical field component found in the FIREPLACE observations is not spatially confined to the NTFs, providing evidence for a more pervasive vertical field in the GC. From dynamical arguments, we estimate an upper limit on the magnetic field strength for this vertical field, finding B ≤ 4 mG. A field close to this upper limit would indicate that the NTFs are not local enhancements of a weaker background field and that the locations of the NTFs depend on proximity to sites of cosmic-ray production.

New channel selection method of hyperspectral infrared sounders for use in numerical weather prediction

AbstractThis study proposed a new channel selection method by examining explicit analysis results obtained from the assimilation of hyperspectral infrared radiances in a numerical weather prediction model. Initially, this new method was evaluated to expand the limited use of infrared atmospheric sounding interferometer (IASI) channels in the current operational Korean Integrated Model (KIM) data assimilation system. To reduce the computational cost of getting the analysis results, we divided all IASI channels into 20 channel groups using the K‐means clustering algorithm based on the three‐dimensional Jacobian probability density function calculated for each channel. We selected the first channel group with the smallest temperature and humidity analysis errors compared to the ERA5 reanalysis. The channel group that made the smallest errors along with previously selected groups was added sequentially until the additional channel group increased the error. The IASI channel list was expanded to 138 by adding channels sensitive to upper‐tropospheric temperature and mid‐ and upper‐tropospheric water vapor. The impact of the new IASI channel set on the background, analysis, and forecast fields in the KIM was assessed by comparing the results to those obtained using the current operational IASI channels. It was confirmed that the new channels have an overall positive impact on the background and analysis and have improved the KIM forecast accuracy, particularly demonstrating significant improvements in the Northern Hemisphere. Hence, this study potentially provides a new way of channel selection for the assimilation of any future hyperspectral radiances.

General relativistic stochastic thermodynamics

Based on the recent work [J. Stat. Phys. 190, 193 (2023), J. Stat. Phys. 190, 181 (2023)], we formulate the first law and the second law of stochastic thermodynamics in the framework of general relativity. These laws are established for a charged Brownian particle moving in a heat reservoir and subjecting to an external electromagnetic field in generic stationary spacetime background, and in order to maintain general covariance, they are presented respectively in terms of the divergences of the energy current and the entropy density current. The stability of the equilibrium state is also analyzed.

Spurious gauge-invariance and γ5 in dimensional regularization

Dimensional regularization is arguably the most popular and efficient scheme for multi-loop calculations. Yet, when applied to chiral (gauge) theories like the Standard Model and its extensions, one is forced to deal with the infamous “γ5 problem”. The only formulation that has been demonstrated to be consistent at all orders in perturbation theory, known as Breiteinlohner-Maison-’t Hooft-Veltman scheme, is rather cumbersome because of the lack of manifest chiral gauge-invariance. In this paper we point out that this drawback can be alleviated by the introduction of auxiliary fields that restore a spurious version of gauge-invariance. If combined with the background field method, all 1PI amplitudes and the associated counterterms are formally covariant and thus severely constrained by the symmetries. As an illustration we evaluate the symmetry-restoring counterterms at 1-loop in the most general renormalizable gauge theory with Dirac fermions and scalar fields, the Standard Model representing a particular example.

Gradient corrections to the quantum effective action

We derive the quantum effective action up to second order in gradients and up to two-loop order for an interacting scalar field theory. This expansion of the effective action is useful to study problems in cosmological settings where spatial or time gradients are important, such as bubble nucleation in first-order phase transitions. Assuming spacetime dependent background fields, we work in Wigner space and perform a midpoint gradient expansion, which is consistent with the equations of motion satisfied by the propagator. In particular, we consider the fact that the propagator is non-trivially constrained by an additional equation of motion, obtained from symmetry requirements. At one-loop order, we show the calculations for the case of a single scalar field and then generalise the result to the multi-field case. While we find a vanishing result in the single field case, the one-loop second-order gradient corrections can be significant when considering multiple fields. As an example, we apply our result to a simple toy model of two scalar fields with canonical kinetic terms and mass mixing at tree-level. Finally, we calculate the two-loop one-particle irreducible (1PI) effective action in the single scalar field case, and obtain a nonrenormalisable result. The theory is rendered renormalisable by adding two-particle irreducible (2PI) counterterms, making the 2PI formalism the right framework for renormalization when resummed 1PI two-point functions are used in perturbation theory.

Theoretical Studies on the Evolution of Solar Filaments in Response to New Emerging Flux

Abstract New emerging flux (NEF) has long been considered a mechanism for solar eruptions, but the detailed process remains an open question. In this work, we explore how NEF drives a coronal magnetic configuration to erupt. This configuration is created by two magnetic sources of strengths M and S embedded in the photosphere, one electric-current-carrying flux rope (FR) floating in the corona, and an electric current induced on the photospheric surface by the FR. The source M is fixed, accounting for the initial background field, and S changes, playing the role of NEF. We introduce the channel function C to forecast the overall evolutionary behavior of the configuration. The location, polarity, and strength of NEF govern the evolutionary behavior of the FR before eruption. In the case of ∣S/M∣ < 1, with reconnection occurring between new and old fields, the configuration in equilibrium evolves to the critical state, invoking the catastrophe. In this case, if the polarities of the new and old fields are opposite, reconnection occurs as NEF is close to the FR, and if the polarities are the same, reconnection happens as NEF appears far from the FR. With different combinations of the relative polarity and the location, the evolutionary behavior of the system gets complex, and the catastrophe may not occur. If ∣S/M∣ > 1 and the two fields have opposite polarity, the catastrophe always takes place, but if the polarities are the same, the catastrophe occurs only as NEF is located far from the FR; otherwise, the evolution ends up either with a failed eruption or without a catastrophe at all.

Sensitivity of two-mode SRF cavity to generic electromagnetism of sub-μeV dark matter

The low-mass dark matter (DM) such as axion or wave-like scalar is a plausible DM candidate. Recently, the possible non-standard couplings of low-mass DM has drawn much attention. In this work we investigate the detection of electromagnetic couplings in a few benchmark models of low-mass DM. For illustration, we consider the generic axion electrodynamics including CP-violating coupling as well as the newly proposed axion electromagnetodynamics. The superconducting radio frequency (SRF) cavity with two modes has more advantages than the traditional cavity approach with static background field. We utilize the two-mode SRF cavity to probe the generic couplings of low-mass DM with frequency lower than GHz. We show the sensitivity of the SRF cavity to the axion couplings in the above frameworks.

The causal effects of gut microbiota on quantitative susceptibility mapping (QSM) and T2* imaging-derived phenotypes: insights from a Mendelian randomization study.

Gut microbiota are associated with brain imaging-derived phenotypes (IDPs); however, the specific causal relationship between the gut microbiota and brain iron-related IDPs remains unclear. Thus, we sought to analyze the potential causal effects of gut microbiota on brain iron-related IDPs using Mendelian randomization (MR). We obtained the data of 196 gut microbiota from a genome-wide association study (GWAS) from the MiBioGen database, as well as the data of 18 quantitative susceptibility mapping (QSM) IDPs and 10 T2* IDPs from the United Kingdom Biobank (UKB). We then conducted one-way two-sample MR analyses to examine their causal interactions. To guarantee the robustness of the results, we performed two independent analysis processes by selecting statistically significant instrumental variables (IVs) with a distinct level of statistical strictness, and derived the intersection of these two analyses. Our results showed that the genus Howardella was positively correlated with the median susceptibility in the right caudate [β: 0.0935, 95% confidence interval (CI): 0.0601, 0.1269, Pinverse variance weighting (IVW)=4.00E-08]; the genus Dialister was positively correlated with the median susceptibility in the right accumbens (β: 0.0949, 95% CI: 0.0575, 0.1324, PIVW=6.90E-07); the genus Butyricicoccus was positively associated with the median T2* in the left hippocampus with the additional deconfounding of the background field gradient (β: 0.1543, 95% CI: 0.0959, 0.2127, PIVW=2.20E-07); the genus Desulfovibrio was positively related to the T2* white matter hyperintensity (WMH) IDP with WMH volume regressed out (β: 0.1168, 95% CI: 0.0697, 0.1639, PIVW=1.20E-06). Notably, both the family Defluviitaleaceae (β: -0.1215, 95% CI: -0.1604, -0.0827, PIVW=8.40E-10) and genus DefluviitaleaceaeUCG011 (β: -0.1142, 95% CI: -0.1614, -0.0670, PIVW=2.10E-06) were negatively correlated with the median T2* in the right accumbens with the additional deconfounding of the background field gradient. This study found genetic evidence that gut microbiota dysbiosis has causal effects on brain iron-related IDPs. Our findings provide novel insights into the diagnosis and therapeutic management of central nervous system (CNS) diseases.

Low-energy limit of N-photon amplitudes in a constant field: Part II

We employ the worldline formalism to derive a series representation of the low-energy limit of the N-photon amplitude in a constant background field for both scalar and spinor QED. The amplitudes are then written in terms of a single proper-time integral. The above-mentioned series representation terminates when considering a constant crossed field. This allows us to obtain even more compact expressions for these particular amplitudes for which the result of the proper-time integral, for fixed parameters, takes the form of a factorial function. In addition, we derive all helicity components of these amplitudes and express them explicitly in terms of Bernoulli numbers and spinor products.

Benchmark Dataset Applied to Quantitative Precipitation Estimation and Forecasting of Qinghai

We collected short-duration heavy precipitation events around weather radar since 2020 and get radar base data of these events. Then, we extracted radar products like Composite Reflectivity (CR), echo top height (ET) and Vertically Integrated Liquid Water (VIL) from radar base data after quality control as the input of dataset, and merge the surface precipitation of 6 minutes with background field using multi-grid variation to generate precipitation label by 6 minutes. Thus, we constructed two datasets artificial intelligence application QpefQH for short-duration heavy precipitation. QpefQH dataset has a scale of more than 15,000 images available for radar echo extrapolation and quantitative precipitation estimation tasks based on deep learning. QpefQH dataset also includes multi-source data such as satellite, numerical model, sounding, lightning, land surface temperature, pressure, wind and other observation data. QpefQH can be shared as a benchmark dataset for artificial intelligence research on short-duration heavy precipitation in Qinghai Province.

Probing CPT Invariance with Top Quarks at the LHC.

The first model-independent sensitivity to CPT violation in the top-quark sector is extracted from ATLAS and CMS measurements of the top and antitop kinematical mass difference. We find that the temporal component of a CPT-violating background field interacting with the top-quark vector current is restricted within the interval [-0.13,0.29] GeV at 95% confidence level.

Investigating Tropical Cyclone Warm Core and Boundary Layer Structures with Constellation Observing System for Meteorology, Ionosphere, and Climate 2 Radio Occultation Data

The Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC-2) collects data covering latitudes primarily between 40 degrees north and south, providing abundant data for tropical cyclone (TC) research. The radio occultation data provide valuable information on the boundary layer. However, quality control of the data within the boundary layer remains a challenging issue. The aim of this study is to obtain a more accurate COSMIC-2 radio occultation (RO) dataset through quality control (QC) and use this dataset to validate warm core structures and explore the planetary boundary layer (PBL) structures of TCs. In this study, COSMIC-2 data are used to analyze the distribution of the relative local spectral width (LSW) and the confidence parameter characterizing the random error of the bending angle. An LSW less than 20% is set as a data QC threshold, and the warm core and PBL composite structures of TCs at three intensities in the Northwest Pacific Ocean are investigated. We reproduce the warm core intensity and warm core height characteristics of TCs. In the radial direction of the typhoon eyewall, the impact height of the PBL increases from 3.45 km to 4 km, with the tropopause ranging from 160 hPa to 100 hPa. At the bottom of the troposphere, the variations in the positive and negative bias between the RO-detected and background field bending angles correspond well to the PBL heights, and the variations in the positive bias between the RO-detected and background field refractivity reach 14%. This research provides an effective QC method and reveals that the bending angle is sensitive to the PBL height.

QCD with 2+1 flavors at the physical point in external chromomagnetic fields

We investigate full quantum chromodynamics (QCD) with (2+1)-flavor of highly improved staggered quarks fermions at the physical point in the presence of uniform Abelian chromomagnetic background fields. Our focus is to conduct an exploratory study on the renormalized light and strange chiral condensates around the pseudocritical temperature. We find that in the confined region the gauge system is subjected to the chromomagnetic catalysis that turns into the inverse catalysis in the high-temperature regime. We further observe that the chiral condensates are subjected to the so-called thermal hysteresis. Our estimate of the deconfinement temperature indicates that the critical temperature begins to decrease in the small field region, soon after it seems to saturate and finally increase with the strength of the chromomagnetic field. Published by the American Physical Society 2024