Anomalous skew-scattering nonlinear Hall effect in PTPT-symmetric antiferromagnets

Berry curvature and skew-scattering play central roles in determining both the linear and nonlinear anomalous Hall effects. Yet in $PT$-symmetric antiferromagnetic metals, Hall effects from either intrinsic Berry curvature mediated anomalous velocity or the conventional skew-scattering process individually vanish. Here we reveal an unexpected nonlinear Hall effect that relies on both Berry curvature and skew-scattering working in cooperation. This anomalous skew-scattering nonlinear Hall effect (ASN) is $PT$-even and dominates the low-frequency nonlinear Hall effect for $PT$-symmetric antiferromagnetic metals. Surprisingly, we find that in addition to its Hall response, ASN produces helicity dependent photocurrents, in contrast to other known $PT$-even nonlinearities in metals which are helicity blind. This characteristic enables to isolate ASN and establishes new photocurrent tools to interrogate the antiferromagnetic order of $PT$-symmetric metals

Layer photovoltaic effect in van der Waals heterostructures

We argue that the layer electric polarization of noncentrosymmetric layered heterostructures can be generically controlled by light yielding a layer photovoltaic effect (LPE). The LPE possesses a rich phenomenology and can arise from myriad distinct mechanisms displaying strong sensitivity to symmetry (e.g., point group and time-reversal) as well as the presence/absence of a Fermi surface. We systematically classify these and unveil how LPE manifests for a range of light polarizations and even for unpolarized light. These unusual layer photoresponses can be realized in a range of layered heterostructures such as bilayer graphene aligned on hexagonal Boron Nitride and manifest sizeable layer polarization susceptibilities in the terahertz frequency range that can be used as novel means of bulk photodetection.Comment: 8 pages, 2 figure

The dark side of FIRE: predicting the population of dark matter subhaloes around Milky Way-mass galaxies

A variety of observational campaigns seek to test dark-matter models by measuring dark-matter subhaloes at low masses. Despite their predicted lack of stars, these subhaloes may be detectable through gravitational lensing or via their gravitational perturbations on stellar streams. To set measurable expectations for subhalo populations within LambdaCDM, we examine 11 Milky Way (MW)-mass haloes from the FIRE-2 baryonic simulations, quantifying the counts and orbital fluxes for subhaloes with properties relevant to stellar stream interactions: masses down to 10^6 Msun, distances < 50 kpc of the galactic center, across z = 0 - 1 (lookback time 0 - 8 Gyr). We provide fits to our results and their dependence on subhalo mass, distance, and lookback time, for use in (semi)analytic models. A typical MW-mass halo contains ~16 subhaloes >10^7 Msun (~1 subhalo >10^8 Msun) within 50 kpc at z = 0. We compare our results with dark-matter-only versions of the same simulations: because they lack a central galaxy potential, they overpredict subhalo counts by 2-10x, more so at smaller distances. Subhalo counts around a given MW-mass galaxy declined over time, being ~10x higher at z = 1 than at z = 0. Subhaloes have nearly isotropic orbital velocity distributions at z = 0. Across our simulations, we also identified 4 analogs of Large Magellanic Cloud satellite passages; these analogs enhance subhalo counts by 1.4-2.7 times, significantly increasing the expected subhalo population around the MW today. Our results imply an interaction rate of ~5 per Gyr for a stream like GD-1, sufficient to make subhalo-stream interactions a promising method of measuring dark subhaloes.Comment: 13 pages, submitted to MNRA

Constraining the Tilt of the Milky Way's Dark Matter Halo with the Sagittarius Stream

Recent studies have suggested that the Milky Way (MW)'s Dark Matter (DM) halo may be significantly tilted with respect to its central stellar disk, a feature that might be linked to its formation history. In this work, we demonstrate a method of constraining the orientation of the minor axis of the DM halo using the angle and frequency variables. This method is complementary to other traditional techniques, such as orbit fitting. We first test the method using a simulated tidal stream evolving in a realistic environment inside an MW-mass host from the FIRE cosmological simulation, showing that the theoretical description of a stream in the action-angle-frequency formalism still holds for a realistic dwarf galaxy stream in a cosmological potential. Utilizing the slopes of the line in angle and frequency space, we show that the correct rotation frame yields a minimal slope difference, allowing us to put a constraint on the minor axis location. Finally, we apply this method to the Sagittarius stream's leading arm. We report that the MW's DM halo is oblate with the flattening parameter in the potential $q\sim0.7-0.9$ and the minor axis pointing toward $(\ell,b) = (42^{o},48^{o})$. Our constraint on the minor axis location is weak and disagrees with the estimates from other works; we argue that the inconsistency can be attributed in part to the observational uncertainties and in part to the influence of the Large Magellanic Cloud.Comment: 16 pages, 12 figure

Balancing Tumor Control and Protecting Healthy Tissue in Radiotherapy Dosage Optimization

Radiotherapy is an important part of treating cancer because it stops tumors from growing while hurting good cells around them as little as possible. The treatment goal is to give enough radiation to effectively target and kill cancer cells while saving normal tissue from harmful side effects. Optimizing the dose of radiation is a key part of achieving this careful balance. This paper talks about the ideas, problems, and progress made in figuring out the best radiation doses to kill tumors and protect good tissue at the same time. In the past, radiation treatment doses were set by regular guidelines that took into account things like the type, size, and position of the growth. But these methods don\u27t always take into account how different patients\u27 bodies are, how the tumor\u27s environment changes, or how healthy cells change when they are exposed to radiation. To fix this, individual treatment planning, made possible by improvements in imaging methods such as functional MRI and PET scans, is becoming more and more important for finding the best dose. These tools give us a more complete picture of the tumor\u27s location and biology in real time, which can help us apply radiation more precisely. New methods, like intensity-modulated radiotherapy (IMRT), proton treatment, and stereotactic body radiotherapy (SBRT), have made dose distribution more accurate. This means that bigger amounts can be sent to tumors while exposing healthy tissue nearby less. Biological models and dose-painting techniques are also becoming more popular. In these methods, the radiation dose is changed in different parts of the tumor based on how different they are, which makes the treatment even more effective. Even with these improvements, one of the biggest problems still is finding the best balance between the competing goals of controlling tumors and keeping healthy organs safe

On the stability of tidal streams in action space

In the Gaia era it is increasingly apparent that traditional static, parameterized models are insufficient to describe the mass distribution of our complex, dynamically evolving Milky Way (MW). In this work, we compare different time-evolving and time-independent representations of the gravitational potentials of simulated MW-mass galaxies from the FIRE-2 suite of cosmological baryonic simulations. Using these potentials, we calculate actions for star particles in tidal streams around three galaxies with varying merger histories at each snapshot from 7 Gyr ago to the present day. We determine the action-space coherence preserved by each model using the Kullback-Leibler Divergence to gauge the degree of clustering in actions and the relative stability of the clusters over time. We find that all models produce a clustered action space for simulations with no significant mergers. However, a massive (mass ratio prior to infall more similar than 1:8) interacting galaxy not present in the model will result in mischaracterized orbits for stars most affected by the interaction. The locations of the action space clusters (i.e. the orbits of the stream stars) are only preserved by the time-evolving model, while the time-independent models can lose significant amounts of information as soon as 0.5--1 Gyr ago, even if the system does not undergo a significant merger. Our results imply that reverse-integration of stream orbits in the MW using a fixed potential is likely to give incorrect results if integrated longer than 0.5 Gyr into the past

The Debris of the "Last Major Merger" is Dynamically Young

The Milky Way's (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the "last major merger." Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor collided with the MW proto-disk 8-11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the MW disk within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space, because the morphology of debris depends on how long it has had to phase mix. The recently-identified phase-space folds in Gaia DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations at late times. Roughly 20\% of the stars in the prograde local stellar halo are associated with the observed caustics. Based on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1--2 Gyr ago. We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data 1--2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the "last major merger" did not collide with the MW proto-disk at early times, as is thought for the GSE, but instead collided with the MW disk within the last few Gyr, consistent with the body of work surrounding the VRM

Prevalence of antimicrobial resistance genes among Escherichia coli isolated from poultry

Antimicrobial resistance has become a global threat. In the poultry industry, antibiotic usage has been widespread and been used for multiple purposes, viz. growth promoters, therapeutic agent and prophylaxis. This usage has probably led to accumulation of antimicrobial resistant genes. A study on presence of antibiotic resistant genes in poultry farms of Ferozepur and Ludhiana, Punjab were undertaken. A total of 50 faecal samples were collected from eight farms. The samples were processed for isolation of E. coli by using selective media, were identified using various biochemical tests and confirmed with the help of PCR. A total of 35 E. coli isolates were obtained and all were subjected to antibiotic sensitivity test against 10 antibiotics. Also, these isolates were subjected to amplification of antibiotic resistance genes, viz. blaTEM, blaSHV, DHAM, MOXM, sul1, dhfrV, aadA, tetA and tetB using published primers. The isolates revealed resistance to penicillin (100%), ampicillin/sulbactum (100%), erythromycin (94.28%), streptomycin (91.4%), tetracycline (60%), chloramphenicol (60%), trimethoprim (51.4%), co-trimoxazole (48.57%), gentamicin (8.5%) and colistin (8.5%). Seven isolates were found to be positive for blaTEM, nine for sulI, four for dhfrV, 11 for aadA and cmlA, respectively, while none of the isolate showed the blaSHV, DHAM, MOXM, tetA and tetB. The present study revealed that the multiple AMR genes may be prevalent among E. coli isolates of poultry origin which needs urgent attention