More Like this

1. Bounding p-Brauer characters in finite groups with two conjugacy classes of p-elements

   https://doi.org/10.1007/s11856-024-2613-1  

   Hung, Nguyen Ngoc; Sambale, Benjamin; Tiep, Pham Huu (September 2024, Israel Journal of Mathematics)

   Abstract Letk(B₀) andl(B₀) respectively denote the number of ordinary andp-Brauer irreducible characters in the principal blockB₀of a finite groupG. We prove that, ifk(B₀)−l(B₀) = 1, thenl(B₀) ≥p− 1 or elsep= 11 andl(B₀) = 9. This follows from a more general result that for every finite groupGin which all non-trivialp-elements are conjugate,l(B₀) ≥p− 1 or elsep= 11 and$$G/{{\bf{O}}_{{p^\prime }}}(G) \cong C_{11}^2\, \rtimes\,{\rm{SL}}(2,5)$$ $G/O_{p^{\prime }}\left(G\right)\cong C_{11}^2⋊\text{SL}(2,5)$. These results are useful in the study of principal blocks with few characters. We propose that, in every finite groupGof order divisible byp, the number of irreducible Brauer characters in the principalp-block ofGis always at least$$2\sqrt {p - 1} + 1 - {k_p}(G)$$ $2\sqrt{p-1}+1-k_p\left(G\right)$, wherek_p(G) is the number of conjugacy classes ofp-elements ofG. This indeed is a consequence of the celebrated Alperin weight conjecture and known results on bounding the number ofp-regular classes in finite groups. 

   more » « less
2. Constraining Cosmological Parameters Using the Cluster Mass–Richness Relation

   https://doi.org/10.3847/1538-4357/ace773  

   Abdullah, Mohamed H.; Wilson, Gillian; Klypin, Anatoly; Ishiyama, Tomoaki (September 2023, The Astrophysical Journal)

   Abstract The cluster mass–richness relation (MRR) is an observationally efficient and potentially powerful cosmological tool for constraining the matter density Ω_mand the amplitude of fluctuationsσ₈using the cluster abundance technique. We derive the MRR relation usingGalWCat19, a publicly available galaxy cluster catalog we created from the Sloan Digital Sky Survey-DR13 spectroscopic data set. In the MRR, cluster mass scales with richness as $\log M_{200}=\alpha +\beta \log N_{200}$. We find that the MRR we derive is consistent with both the IllustrisTNG and mini-Uchuu cosmological numerical simulations, with a slope ofβ≈ 1. We use the MRR we derived to estimate cluster masses from theGalWCat19catalog, which we then use to set constraints on Ω_mandσ₈. Utilizing the all-member MRR, we obtain constraints of Ω_m= ${0.31}_{-0.03}^{+0.04}$andσ₈= ${0.82}_{-0.04}^{+0.05}$, and utilizing the red member MRR only, we obtain Ω_m= ${0.31}_{-0.03}^{+0.04}$andσ₈= ${0.81}_{-0.04}^{+0.05}$. Our constraints on Ω_mandσ₈are consistent and very competitive with the Planck 2018 results. 

   more » « less
3. Ferrimagnetism and Half-metallicity in Cr-substituted Mn _4–x Cr _x Al ₁₁

   https://doi.org/10.1088/1361-648X/add8d8  

   Noor, Md_Fahel_Bin; Law, Ka_Ming; Yasmin, Nusrat; Hauser, Adam_J; Besara, Tiglet (May 2025, Journal of Physics: Condensed Matter)

   Abstract Single crystals of disordered Mn_4–xCr_xAl₁₁have been synthesized via the flux method. EDS on several crystals of various sizes and shapes revealed an average molar ratio of 17:9:74 for Mn:Cr:Al, while X-ray diffraction on three different crystals yield compositions Mn_2.26Cr_1.74Al₁₁(Mn_4–xCr_xAl₁₁,x= 1.74), Mn_0.83Cr_3.17Al₁₁, and Mn_1.07Cr_2.93Al₁₁. This compound crystallizes in space groupP–1, isostructural with both Mn₄Al₁₁and Cr₄Al₁₁. Magnetic measurements on several crystals show that this disordered compound is ferrimagnetic with a low effective moment ofμ_eff≈1.012±0.004 μ_B/f.u. and a non-reachable transition temperature. DFT calculations display opening of a bandgap in the spin-up channel near the Fermi level with increasing Cr content, an indication of half-metallicity. 

   more » « less
4. Kepler and the Behemoth: Three Mini-Neptunes in a 40 Million Year Old Association

   https://doi.org/10.3847/1538-3881/ac93ff  

   Bouma, L G; Kerr, R; Curtis, J L; Isaacson, H; Hillenbrand, L A; Howard, A W; Kraus, A L; Bieryla, A; Latham, D W; Petigura, E A; et al (October 2022, The Astronomical Journal)

   Abstract Stellar positions and velocities from Gaia are yielding a new view of open cluster dispersal. Here we present an analysis of a group of stars spanning Cepheus (l= 100°) to Hercules (l= 40°), hereafter the Cep-Her complex. The group includes four Kepler objects of interest: Kepler-1643 b (R_p= 2.32 ± 0.13R_⊕,P= 5.3 days), KOI-7368 b (R_p= 2.22 ± 0.12R_⊕,P= 6.8 days), KOI-7913 Ab (R_p= 2.34 ± 0.18R_⊕,P= 24.2 days), and Kepler-1627 Ab (R_p= 3.85 ± 0.11R_⊕,P= 7.2 days). The latter Neptune-sized planet is in part of the Cep-Her complex called theδLyr cluster. Here we focus on the former three systems, which are in other regions of the association. Based on kinematic evidence from Gaia, stellar rotation periods from TESS, and spectroscopy, these three objects are also ≈40 million years (Myr) old. More specifically, we find that Kepler-1643 is ${46}_{-7}^{+9}$Myr old, based on its membership in a dense subcluster of the complex called RSG-5. KOI-7368 and KOI-7913 are ${36}_{-8}^{+10}$Myr old, and are in a diffuse region that we call CH-2. Based on the transit shapes and high-resolution imaging, all three objects are most likely planets, with false-positive probabilities of 6 × 10⁻⁹, 4 × 10⁻³, and 1 × 10⁻⁴for Kepler-1643, KOI-7368, and KOI-7913, respectively. These planets demonstrate that mini-Neptunes with sizes of ≈2 Earth radii exist at ages of 40 Myr. 

   more » « less
5. JWST Photometric Time-delay and Magnification Measurements for the Triply Imaged Type Ia “SN H0pe” at z = 1.78

   https://doi.org/10.3847/1538-4357/ad3c43  

   Pierel, J_D_R; Frye, B_L; Pascale, M.; Caminha, G_B; Chen, W.; Dhawan, S.; Gilman, D.; Grayling, M.; Huber, S.; Kelly, P.; et al (May 2024, The Astrophysical Journal)

   Abstract Supernova (SN) SN H0pe is a gravitationally lensed, triply imaged, Type Ia SN (SN Ia) discovered in James Webb Space Telescope imaging of the PLCK G165.7+67.0 cluster of galaxies. Well-observed multiply imaged SNe provide a rare opportunity to constrain the Hubble constant (H₀), by measuring the relative time delay between the images and modeling the foreground mass distribution. SN H0pe is located atz= 1.783 and is the first SN Ia with sufficient light-curve sampling and long enough time delays for anH₀inference. Here we present photometric time-delay measurements and SN properties of SN H0pe. Using JWST/NIRCam photometry, we measure time delays of Δt_ab= $-{116.6}_{-9.3}^{+10.8}$observer-frame days and Δt_cb= $-{48.6}_{-4.0}^{+3.6}$observer-frame days relative to the last image to arrive (image 2b; all uncertainties are 1σ), which corresponds to a ∼5.6% uncertainty contribution forH₀assuming 70 km s⁻¹Mpc⁻¹. We also constrain the absolute magnification of each image toμ_a= ${4.3}_{-1.8}^{+1.6}$,μ_b= ${7.6}_{-2.6}^{+3.6}$,μ_c= ${6.4}_{-1.5}^{+1.6}$by comparing the observed peak near-IR magnitude of SN H0pe to the nonlensed population of SNe Ia. 

   more » « less