Earth and Planetary Astrophysics
Does HD 3167 Have Planets with Perpendicular Orbits?
Joshua N. Winn, Jack Lubin, Gu{\dh}mundur Stefánsson et al. (+5 more)
The two transiting
planets of HD 3167 were reported to follow nearly perpendicular paths, with the inner orbit aligned with the
stellar equator and the outer orbit nearly polar. This interpretation depends critically on a challenging single-transit detection of the Rossiter-McLaughlin effect of the inner
planet. We observed three additional transits of the inner
planet with the Keck
Planet Finder and analyzed the new data together with two archival ESPRESSO transit
datasets. We do not confirm the previously reported low obliquity. Our analysis favors a projected obliquity of $-66^{+14}_{-12}$ degrees, consistent with coplanar orbits. However, because the best-fit projected rotation velocity is higher than expected, and because the obliquity uncertainty grows substantially when the most discrepant of the five transit
datasets is omitted, we regard the geometry of the HD 3167 system as still unsettled.
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All authors Joshua N. Winn, Jack Lubin, Gu{\dh}mundur Stefánsson, Haochuan Yu, Erik Petigura, Howard Isaacson, Andrew W. Howard, Fei Dai
Cosmology and Nongalactic Astrophysics
Generalised Visibility ILC: a new foreground mitigation strategy for interferometric HI intensity mapping in the low-redshift Universe
M. Ruiz-Granda, A. Mazumder, L. Wolz et al. (+3 more)
HI intensity mapping is a powerful probe of the large-scale matter distribution and of the underlying astrophysics and cosmology. However, its application is limited by the challenge of separating the faint neutral hydrogen (HI) signal from much brighter foreground emission. We present a new non-parametric foreground-cleaning method in visibility space for low-
redshift HI intensity mapping and apply it to interferometric MeerKAT and SKA-Mid-like simulations. Our newly-developed Generalised Visibility Internal Linear Combination (GVILC) method combines Principal Component Analysis (PCA) for foreground subspace identification, informed by a prior HI signal-plus-noise covariance
matrix, with a multi-dimensional ILC in visibility space to suppress foregrounds and recover the HI signal with reduced contamination. The number of modes to remove in the PCA is calculated using a data-driven statistical approach, leading to significant foreground residual suppression with limited HI signal loss. Moreover, GVILC in combination with foreground avoidance can prevent most of the signal loss, while simultaneously recovering modes that were initially contaminated by foregrounds. The mean squared error statistic shows that for both MeerKAT and SKA-Mid-like simulations, GVILC outperforms the foreground avoidance only strategy. We find that including a more realistic HI model with line broadening and spatial correlations between HI and continuum sources leads to increased signal loss after foreground removal, without affecting the number of modes removed by GVILC. This paper demonstrates that GVILC is an effective method to clean foreground contamination in HI intensity mapping with
radio interferometric data, enabling the recovery of cosmological information from previously inaccessible regions of
Fourier space.
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All authors M. Ruiz-Granda, A. Mazumder, L. Wolz, M. Remazeilles, D. Herranz, P. Vielva
High Energy Physics (Theory)
Sphere path integrals for fermionic gauge fields
Chiara Baracco and Vasileios A. Letsios
We consider
spin-$s \geq \frac{3}{2}$ complex, strictly massless fermionic gauge fields on the four-sphere, $S^4$, which is the Euclidean continuation of de Sitter spacetime, dS$_4$. For $s=\frac{5}{2}$, after briefly discussing different options for the quantisation of the theory on dS$_4$, we compute the one-loop sphere path integral. We explain how it can be expressed in terms of functional determinants, generalising previous results for $s=\frac{3}{2}$. We proceed to rewrite the result in terms of `bulk'
unitary Harish-Chandra characters in the discrete series of the de Sitter isometry group, $Spin(4,1)$, and `edge' characters. We then generalise the character expression of the sphere path integral for any complex, strictly massless
spin-$s\geq\frac{3}{2}$ fermionic gauge potential. Additionally, we compute the coefficient of the logarithmic divergence of the $S^4$ path integral for all
spin-$s \geq \frac{3}{2}$, and we show that it is fully encoded by bulk and edge characters. We further show that at one loop no imaginary phase appears for strictly massless fermionic gauge potentials, contrary to the case of
bosons. Lastly, we confirm the exact one-loop cancellation between bulk and edge contributions for the case of an infinite tower of complex massless
fermions of
spins $s=\frac{1}{2}, \frac{3}{2},\dots$, observed recently.
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Astrophysics of Galaxies
M. L. L. Dantas, J. J. García-Delgado, I. Rebollido et al. (+1 more)
Stars observed in the
solar vicinity were not necessarily born there. Radial mixing can redistribute
stellar populations across the
Galactic disc, decoupling their present-day locations from the environments in which they formed. We summarise a framework that combines
Galactic chemical
evolution models with a generalised additive model to infer
stellar birth radii. We apply it to 1327 predominantly thin-disc
planet hosts with homogeneous ages,
Gaia DR3 astrometry, and SWEET-Cat atmospheric parameters. We find that
giant-
planet systems preferentially trace metal-rich inner-disc birth environments, whereas rocky-only systems are less centrally concentrated; and no clear relation between radial displacement and detected
planet multiplicity.
Planet-host
stars that migrate towards the inner parts of the
Galaxy have systems with larger orbital separations; however, this may partly reflect the known dependence of planetary orbital properties on host-
star metallicity rather than a causal effect of
Galactic stellar migration. These results illustrate how
Galactic archaeology can complement
exoplanet demographics by linking planetary systems to their probable birth environments.
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All authors M. L. L. Dantas, J. J. García-Delgado, I. Rebollido, R. Smiljanic
General Relativity and Quantum Cosmology
Bosonic stars with dark electroweak fields
Etevaldo dos Santos Costa Filho and Romain Gervalle
We construct bosonic
stars in the Einstein-Weinberg-Salam theory, namely the bosonic sector of the electroweak Standard Model minimally coupled to Einstein's theory of
gravity. These configurations are everywhere regular, spherically symmetric and asymptotically flat, consisting of a static condensate of the massive $W$ and $Z$
bosons, whose masses arise from the
Higgs mechanism. Although the corresponding fields exist in nature, gravitational effects are negligible at the physical electroweak scale and the configurations would be microscopic. Keeping Newton's constant and the electroweak mass ratios at their physical values, we therefore interpret the model as the bosonic sector of a dark electroweak theory with a radically different energy scale. Choosing the ultralight vector
boson mass $m_{\mathrm{W}}c^{2}=8.7\times10^{-13}\,$eV, as suggested by the Proca
star interpretation of GW190521, our bosonic
stars can attain masses in the intermediate-mass black hole range.
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High Energy Physics (Phenomenology)
Probing Scalar-Induced First-Order Phase Transitions with the Diffuse Supernova Neutrino Background
Sudipta Das, Shamik Niyogi and Manibrata Sen
We investigate the possibility of probing a scalar-induced first-order phase transition (FOPT) inside core-collapse
supernovae through the diffuse
supernova neutrino background (DSNB). We consider a light scalar coupled to
neutrinos that is produced and thermalised in the proto-
neutron-
star core. This leads to two distinct
neutrino components: a
prompt contribution from thermally produced scalars and a delayed, spectrally narrow contribution from the decay of coherent scalar excitations due to the FOPT. We study the resulting DSNB signal at Super-Kamiokande, Hyper-Kamiokande, and DUNE, finding a strong dependence on the
neutrino mass ordering. The recent Super-Kamiokande data already constrain the scalar parameter space for inverted ordering and quasi-degenerate
neutrino masses, while future detectors can significantly improve this sensitivity. Our results demonstrate that DSNB measurements can provide a novel probe of finite-temperature scalar dynamics in core-collapse
supernovae.
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High Energy Physics (Phenomenology)
Lukewarm inflation, primordial black holes and gravitational waves
Paulo B. Ferraz, António Torres Manso and João G. Rosa
We show that a secondary period of warm inflation, at temperatures parametrically below the GUT scale, may not only dilute any unwanted thermal relics formed after reheating but also significantly enhance the power spectrum of
primordial curvature perturbations on small scales. The latter is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a
stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-
solar mass
primordial black holes (PBHs). This scenario could, in particular, explain the NANOGrav signal if it persists at much higher frequencies with a comparable magnitude, up to a sharp cut-off, $f_{max}$. The associated PBH mass distribution may exhibit either a peak at a mass $M_*\propto f_{max}^{-2}$ or a broad plateaux above this mass threshold, depending on the spectral tilt. Moreover, in this scenario the NANOGrav signal is compatible with a significant fraction of dark matter in PBHs in the asteroid- and planetary-mass ranges.
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High Energy Physics (Phenomenology)
SHiP as a (post-)discovery machine: identifying the diphoton signals' origin
Matei Climescu, Malte Fogde Mikkelsen and Maksym Ovchynnikov
The upcoming SHiP experiment may probe interaction strengths of decaying feebly coupled particles several orders of magnitude below existing limits. In the event of a discovery, it may also reveal the nature of the new particle. This requires identifying its exact production mechanism, which SHiP does not observe directly. We explore whether this mechanism can be inferred from the kinematics of its visible decays. As a
benchmark, we consider an
axion-like particle (ALP) with a dominant diphoton decay, which may occur for couplings to the $U(1)_Y$ and $SU(2)_L$ gauge fields. For a known ALP mass, the observed energy and angular distributions depend on the relative magnitude and sign of the couplings and on the unknown lifetime, which we profile independently under each hypothesis. We first determine how the ALP energy and its longitudinal and transverse decay positions distinguish the interactions, assuming perfect reconstruction and accounting for production, propagation, decay, and
geometric acceptance. We then include the detector response and reconstruct the diphoton decays using a full simulation of the SHiP electromagnetic calorimeter. Only $2$–$4$ reconstructed diphoton events are needed to distinguish the two pure $U(1)_{Y}$ and $SU(2)_{L}$ interactions for ALP masses between $0.2$ and $1~\mathrm{GeV}$. For coupling admixtures, the study assuming perfect reconstruction indicates requirements of several tens to $\mathcal{O}(10^2)$ events in favorable regions.
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Solar and Stellar Astrophysics
A census of massive eclipsing binaries in the Whirlpool Galaxy
Cheyanne Shariat, Kareem El-Badry, Maude Gull et al. (+3 more)
We present a census of massive eclipsing binary (EB) candidates in the Whirlpool
Galaxy (M51), a face-on spiral
galaxy at 7.5 Mpc with $Z\sim Z_\odot$. Using 34 epochs of red-optical Hubble Space
Telescope (HST) photometry and a single epoch of broadband UV-optical photometry, we identify 173 massive EB candidates ($>5~{\rm M_\odot}$) with orbital periods $P_{\rm orb}$=1-30 days. The sample traces young
stellar populations across the spiral arms of M51. Joint light-curve and spectral energy distribution fits for 136 systems yield binaries spanning $T_{\rm eff}=10{,}000$-$50{,}000$ K, $R=7$-$66~{\rm R_\odot}$, and masses of $5$-$120~{\rm M_\odot}$. We use detailed injection-recovery simulations to quantify the survey's completeness and infer intrinsic properties of the massive binary population. At the population level, we infer a close-binary fraction of $f_{\rm close}=27.4\pm7.1\%$ for $2\leq P_{\rm orb}/{\rm d}<20$ and $0.1\leq q\leq1$. Over the same period range, the intrinsic period distribution is consistent with being log-uniform, ${\rm d}N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^{\pi}$ with $\pi=0.29\pm0.32$. These demographics broadly match those of massive-
star populations in the Milky Way, LMC, and SMC, with tentative evidence for a lower close-binary fraction at lower
metallicity. Across the $\sim0.2$-$1.1~Z_\odot$ range spanned by these
galaxies, the overall similarities suggest that the formation of close massive binaries depends only weakly on
metallicity. Our survey establishes EBs as a powerful tool for measuring massive-binary demographics beyond the Local Group and provides a rich panchromatic census of $\sim$100,000 luminous
stars and variables in M51.
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All authors Cheyanne Shariat, Kareem El-Badry, Maude Gull, Daniel R. Weisz, Charlie Conroy, Alessandro Savino
High Energy Physics (Theory)
Algebraic Complexity and Black Hole Complementarity
Aude Corbeel, Jingxin Tu, Pim van den Heuvel et al. (+2 more)
We develop an operator algebraic generalization of the Yoshida-Kitaev information recovery protocol that applies to von Neumann
algebras of arbitrary type. The construction is based on finite-index inclusions, with the Jones basic construction and canonical endomorphisms providing the central algebraic tools. Unlike the finite-dimensional
qubit description, the infinite-dimensional theory exhibits new structural phenomena that play an essential role in information recovery. In particular, the diary information is represented non-locally by a choice of Pimsner-Popa basis associated with the inclusion. Exploiting the Temperley-Lieb relations satisfied by the Jones projections, we introduce an algebraic notion of computational complexity and show that it is naturally measured by the Jones-Kosaki index. For irreducible depth-two inclusions, we demonstrate that the information transfer is implemented by an algebraic
Fourier transform. Finally, we discuss a potential spacetime interpretation of the construction, including the emergence of an island
algebra in terms of (non-)isometric
embeddings and an operator algebraic realization of black hole complementarity.
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All authors Aude Corbeel, Jingxin Tu, Pim van den Heuvel, Jeremy van der Heijden, Erik Verlinde
High Energy Physics (Theory)
Strong coupling spectrum of $\mathrm{AdS}_3\times \mathrm{S}^3$ from string field theory
Luis F. Alday, Shai M. Chester, Kiarash Naderi et al. (+1 more)
We consider type IIB string theory on $\mathrm{AdS}_3\times \mathrm{S}^3\times \mathbb{T}^4$ in a large AdS radius expansion at arbitrary values of the relative RR and NS-NS fluxes. We develop a method for computing scaling dimensions in the dual CFT in this limit by combining a string field theory calculation, valid at finite quantized NS-NS flux but perturbative in RR flux, with a finite mixed-flux ansatz, which is constrained by worldsheet parity and motivated by classical string solutions. We apply the method to three families of states. In the pure-RR limit, our results agree both with a family of states computed using the worldsheet bootstrap and with another family computed using integrability.
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All authors Luis F. Alday, Shai M. Chester, Kiarash Naderi, De-liang Zhong
Astrophysics of Galaxies
A model to mini-quench early galaxies by balancing stellar feedback and gas accretion
Judah Luberto and Steven R. Furlanetto
The James Webb Space
Telescope (JWST) has discovered a population of low-mass, early
galaxies with very low levels of
star formation over tens of Myr. These "mini-quenched"
galaxies were one of the many surprises from JWST and still require a robust explanation. We seek to explain a few important properties of these
galaxies, namely the timescales governing their
star formation and quenching. We use a simple model that pairs
stellar feedback with the forces binding gas to a $z \sim 6$
galaxy, and with plausible parameter choices, this model produces mini-quenching in
galaxies approximately as large as observed mini-quenched
galaxies – up to total
stellar masses of $\sim 10^{10} M_{\odot}$. In our model, the ejected interstellar gas forms into a spherical shell that expands outward during quenching. Our novel improvement is allowing this expanding shell to prevent accreting gas from falling in, in contrast to other models whose shells do not interact with accreting gas. Using our model, if a
galaxy accretes isotropically, we find that
stellar feedback can reproduce observed timescales of mini-quenching with plausible
galaxy-formation parameter values. However, at low
halo masses, the quenching timescale of our model is too long ($> 100$ Myr). A potential solution for a long quenching time is for the
galaxy to accrete via filaments, in which case only a portion of the shell interacts with the accreting gas and the quenching timescale decreases to more accepted values. However, the ram pressure from feedback cannot stop filaments with very small opening angles, as occur in some
halo formation models, making mini-quenching impossible. Finally, we use this model to estimate the fraction of
galaxies undergoing mini-quenching, finding that it can be large.
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Strongly Correlated Electrons
Bad metallicity in the semi-quantum regime of the Hubbard model
Evyatar Tulipman, Vadim Oganesyan, Thomas P. Devereaux et al. (+1 more)
Bad metals exhibit approximately $T$-linear dc resistivity beyond the Ioffe–Regel limit. That this behavior occurs in systems with radically different ground states suggests it is a generic manifestation of strong local correlations. We test this hypothesis in the infinite-$U$ Hubbard model with small hole densities using exact diagonalization to compute thermodynamic and transport properties of finite clusters. Upon cooling, we find an intermediate temperature range, an electronic analogue of the “semi-
quantum regime” of
liquid helium, in which
quantum effects produce a roughly $T$-independent compressibility, yet the resistivity is $T$-linear and exceeds the Ioffe–Regel limit. Entry into this regime is accompanied by the formation of quasi-local
ferromagnetic “
spin cages” around doped holes, regions that facilitate local
quantum motion embedded in a fluctuating
spin background, analogous to the transient crystalline cages thought to control incoherent transport in semi-
quantum liquid helium. Remarkably, despite the simplicity of the model, the bad metal behavior found here resembles that seen in various material platforms.
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All authors Evyatar Tulipman, Vadim Oganesyan, Thomas P. Devereaux, Steven A. Kivelson
High Energy Astrophysical Phenomena
A Significant Dust Reservoir Uncovered with JWST in the Type Ic SN 1983V More Than 40 Years Post-Explosion
Sophia S. Kressy, Thomas Moore, Ori D. Fox et al. (+26 more)
Searching for late-time emission from
supernovae (SNe) is an active field. Infrared (IR) wavelengths are sensitive to thermal emission from
dust, which can be used to probe SN contributions to the
cosmic dust budget and progenitor mass-loss histories. The older an SN, the more likely it is for any existing
dust to have cooled below the detection threshold of most observatories, even JWST. Decades-old IR observations of SNe are therefore exceedingly rare. Here we present fortuitous and serendipitous JWST IR observations that detect a point source at the position of the Type Ic SN 1983V more than 40 yr post-explosion. We demonstrate that the source is unlike nearby HII regions and likely to be the dusty SN. We further show evidence from archival HST data of a plausible H/alpha counterpart associated with ongoing SN shock interaction that collisionally heats the
dust. In this scenario, the
dust is distributed in a
torus, more consistent with mass loss from binary interaction than a spherical wind. While not the oldest SN detected by JWST (SN 1980K), SN 1983V is a close second. Moreover, it has a relatively large
dust mass (~7.7 x 10^-3 M_
solar), particularly for a stripped-envelope SN. Although the
dust is not likely newly formed, it does suggest such systems may contribute to
dust production, particularly in the early Universe where massive
stars and binary systems were more common. Spectroscopic observations can ultimately confirm the SN nature of this source.
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All authors Sophia S. Kressy, Thomas Moore, Ori D. Fox, Nathan Smith, Raphael Baer-Way, Luc Dessart, Michael J. Dulude, W. V. Jacobson-Galán, Melissa Shahbandeh, Tea Temim, Chris Ashall, David A. Coulter, Alexei V. Filippenko, Sebastian Gomez, Jacob Jencson, Kyle Medler, Daniel Patnaude, Tamás Szalai, Schuyler D. Van Dyk, Aiden Agostinelli, Sarah Healy, Zachary G. Lane, Dan Milisavljevic, Shazrene Mohamed, Benjamin Radmore, Armin Rest, Arkaprabha Sarangi, Yossef Zenati, Noah Zimmer
High Energy Physics (Theory)
Tameness and Complexity in Quantum Field Theory and Gravity
Mick van Vliet
Finiteness appears to play a fundamental role in the mathematical structures underlying the laws of physics. Tame geometry, defined by the theory of o-minimality, provides a framework for making this idea precise. In this thesis we study the concept of tameness and finiteness of complexity across applications in
quantum field theory and
quantum gravity, and demonstrate that many classes of physical functions and theories are tame. To quantify these ideas, we use the novel theory of sharp o-minimality to measure the complexity of physical objects. The analysis covers wavefunctions in
quantum mechanics, classical field configurations, non-perturbative observables in zero-dimensional
quantum field theories, cosmological correlation functions, and Lagrangians of effective field theories. Finally, we argue that the emergence of tameness in physics aligns with manifestations of finiteness in
quantum gravity, converging towards the idea that effective theories of
quantum gravity admit a description of finite complexity. The thesis contains an introductory review for readers who wish to get familiar with tame geometry and its applications to physics.
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High Energy Physics (Theory)
Schwarzschild Black Hole in Uniform Magnetic Field in Einstein-Maxwell-Dilaton Theories
Liang Ma, Peng-Yu Wu and H.Lu
We obtain the Kerr black hole in an external uniform
magnetic field in the Kaluza-Klein (KK) theory via a standard solution-generating technique. Using this as our starting point, we construct exact static solutions describing a Schwarzschild black hole immersed in the external uniform
magnetic field in general string-inspired Einstein-Maxwell-dilaton (EMD) theories, thereby
embedding the static Kerr-Bertotti-Robinson (KBR) solution into the general framework of EMD theories. We also construct electrovacuum solutions involving both electric and
magnetic fields in EMD theories and generalize the system to include mutltiple Maxwell fields and dilatons. These equations of motion can be reduced to Toda-like equations, allowing us to obtain analytic electrovacua associated with Toda equations of all rank-2 Lie groups. We further construct exact solutions of a Schwarzschild black hole immersed in these electrovacua.
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Quantum Gases
Hysteresis in Atomic Josephson Junctions
Vijay Pal Singh, Ludwig Mathey and Luigi Amico
Hysteresis and retrapping are hallmarks of underdamped Josephson dynamics, yet they have remained elusive in atomic Josephson junctions. Here, we introduce a velocity-sweep protocol to demonstrate these phenomena in the underdamped regime of an atomic Josephson junction. Specifically, using classical-field simulations of a two-dimensional bosonic superfluid, we show hysteresis in the velocity-imbalance characteristics and determine the retrapping current. The dynamics are quantitatively captured by the resistively and capacitively shunted junction (RCSJ) model. We show that hysteresis originates from persistent phase slips below the critical current, with the associated dissipation mediated by
vortex-antivortex pair nucleation at the weak link. The retrapping current follows the Stewart-McCumber scaling of underdamped junctions, establishing a common phase-dynamical framework for atomic and superconducting Josephson junctions.
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Cosmology and Nongalactic Astrophysics
On the Clustering Bias of Unresolved Gamma-Ray Sources
Bhashin A. Thakore, Marco Regis, Michela Negro et al. (+4 more)
The Unresolved $\gamma$-Ray Background (UGRB) encodes the collective emission of source populations that are too faint to be detected individually, and its cross-correlation with tracers of the large-scale structure has emerged as a powerful tool to characterize those populations. In this work, we analyze the weak-
lensing–UGRB cross-correlation using a reference blazar model. By modeling the relation between blazar $\gamma$-ray luminosity and host-
halo mass, we infer the average linear bias $\langle b(z) \rangle$ and host-
halo mass $\langle M(z) \rangle$ of the unresolved blazar population. We find that the signal is dominated by moderately biased sources, with $\langle b \rangle \gtrsim 2$ at $z\simeq 1$, hosted by
halos with $\langle M \rangle \sim \mathcal{O}(10^{13}\,M_\odot)$. Repeating the analysis with a misaligned-AGN model yields consistent bias values, indicating that the result is determined by the clustering properties of the UGRB rather than by the details of the $\gamma$-ray source model.
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All authors Bhashin A. Thakore, Marco Regis, Michela Negro, Stefano Camera, Daniel Gruen, Nicolao Fornengo, Aaron J. Roodman
High Energy Physics (Phenomenology)
A phenomenological profile of Higgs portals at future colliders
Maximilian Detering, Christoph Englert, Victor Maura et al. (+1 more)
Should the
Higgs boson be found to couple to a hidden dark sector, it will become necessary to determine the nature of the
Higgs portal responsible. Could the minimal, marginal
Higgs portal operator be distinguished from a
Higgs portal interaction involving a higher-dimensional operator? This is unlikely for
Higgs portals with on-shell invisible decays to light dark sectors, but for an off-shell
Higgs portal above threshold, where the dark sector is too heavy to contribute to the invisible
Higgs decay width, we find that the higher-dimensional
Higgs portal operators could in principle be differentiated by combining measurements across the integrated programme of HL-LHC, FCC-ee, and FCC-hh. This illustrates the complementarity of precision and high-energy exploration to phenomenologically profile
Higgs portal interactions and probe possible connections between the electroweak scale and a hidden universe.
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All authors Maximilian Detering, Christoph Englert, Victor Maura, Tevong You
Solar and Stellar Astrophysics
The T-GEX project. II. Chrono-chemo-dynamic signatures of UV-bright FGK stars
D. Beltrán, M. L. L. Dantas, R. Smiljanic et al. (+1 more)
We compare the ages, chemical abundances,
Galactic orbits, and inferred birth environments of 37 T-GEX
stars with strong (G1), normal (G2), and intermediate (G3) UV emission. The groups show distinct correlation structures: UV colours correlate with chemical and orbital quantities in G1; G2 has the largest number of significant (anti-)correlations; and no UV-colour correlation reaches the adopted threshold in G3. Most
stars have prograde disc-like orbits, while both
halo-like objects belong to G2. The groups overlap in the [Mg/Fe]-[Fe/H] plane, but G1 is shifted towards lower [Fe/H] and higher [Mg/Fe]. Among the 18 probable thin-disc members, G3 has a smaller median birth radius than G2 (5.70 versus 8.10 kpc), despite their nearly identical median guiding radii ($\langle R_g \rangle$; 8.23 versus 8.25 kpc). All five G1
stars are Ti-enriched compared to Fe, and four combine enhanced Co with comparatively low Mn and, in some cases, Cr. A related but less complete pattern occurs in G3, whereas Co enhancement in some G2
stars does not reproduce the joint signature. The UV-defined groups are heterogeneous and do not correspond to unique
Galactic components. The convergence of $\alpha$-enhancement (likely thick disc members), positive Ti ratios, and the Cr-Mn-Fe-Co-Ni chemical abundance pattern (clearest in G1 but present in related form in G3) supports high-energy core-collapse (i.e. hypernovae) enrichment of the natal material of some UV-excess
stars. Additionally, the smaller G3 birth radii (for those in the
Galactic thin disc) indicate more inward formation regions and provide a possible spatial link to UV-bright
stellar populations in the bulges of spiral
galaxies. Neither result establishes a single causal pathway. Whether mixture-dependent metal-line blanketing connects this enrichment to the UV emission requires tailored spectral modelling.
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All authors D. Beltrán, M. L. L. Dantas, R. Smiljanic, P. B. Tissera
High Energy Physics (Phenomenology)
Damiano F. G. Fiorillo
Compact transient sources, such as
supernovae (SNe) and
neutron star mergers (NSMs), host a population of thermal
neutrinos in their inner cores, which decouple from the dense matter as they stream out. Yet, collisionless does not mean free; their density is large enough to mediate collective waves driven by the coherent weak
neutrino–
neutrino interaction. These collective waves carry little energy, but crucially they transport
flavor.
Neutrinos thus form a collisionless
plasma with
flavor transport driven by
flavor waves, whose quanta are called flavomons $\psi$. The wavelength of these flavomons is much shorter than the characteristic scales of SNe and NSMs, so that a brute-force numerical treatment of the
neutrino plasma is beyond our capabilities. Yet flavomons cannot be neglected, as the stimulated
neutrino decays, schematically $\overline{\nu}_e\to \overline{\nu}_\mu\psi$, cause a rapid buildup in their population, more conventionally called a
flavor instability. We review the theory of the
neutrino plasma, and systematically discuss the instabilities leading to flavomon growth, and connect this emerging quasiparticle description with recent advances in numerical
neutrino flavor kinetics.
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High Energy Physics (Theory)
Deterministic Hypergraph SYK: Melonic Dominance and Maximal Chaos Without Disorder Averaging
Shiroman Prakash
We show that SYK-like melonic solvability and maximal chaos survive in a sparse deterministic model, without disorder averaging. Our deterministic hypergraph SYK model (hSYK) consists of $N$ Majorana
fermions on a $q$-uniform, $d$-regular interaction hypergraph with only $O(dN)$ interaction terms and uniform positive couplings. Under explicit
geometric and spectral expansion conditions, its two-point function satisfies the standard melonic Schwinger-Dyson equation up to $O(d^{-1})$ corrections, while the leading bilocal effective action coincides with that of ordinary SYK at the dominant large-$d$ saddle. Its connected four-point function factorizes into a temporal SYK ladder kernel and a line-graph random walk. A finite line-graph spectral gap controls the visibility of the maximally chaotic uniform mode in generic localized OTOCs and, by gapping non-uniform spatial modes in the bilocal spectrum, excludes additional light fluctuation modes beyond the Schwarzian. Exact diagonalization further shows melonic two-point scaling, single-instance Wigner-Dyson statistics, and the predicted graph-controlled spatial decay of OTOCs. The model therefore offers a disorder-free realization of the essential melonic and chaotic features of SYK, in a form more amenable to
quantum simulation.
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Quantum Physics
Emergent classicality and wavefunction branching in an isolated quantum many-body system
Saúl Pilatowsky-Cameo, Jordan Cotler, Daniel Ranard et al. (+1 more)
Decoherence in
quantum systems is conventionally modeled as the effect of interactions with an external environment. However, such a prescription excludes isolated many-body systems, which are also expected to display classical behavior at macroscopic scales. In isolated systems, decoherence must emerge internally from microscopic degrees of freedom that are invisible to the macroscopic description. Here we explicitly show that classicality can emerge in such a fashion. We consider a weakly disordered, $3$-local chaotic kicked top of $N$
qubits, where the collective
spin sector serves as the macroscopic description, while the microscopic permutation sector acts as an internal bath, decohering the collective
spin sector. Starting from closed
unitary dynamics, we derive and numerically confirm an effective Lindblad equation for the collective
spin variables. In the thermodynamic limit these reduced dynamics converge to a classical chaotic Fokker–Planck equation with vanishingly small
diffusion on the spherical phase space, producing a
quantum-classical correspondence beyond the Ehrenfest time. The chaotic dynamics evolve the pure many-body wavefunction into continuously branching components associated with distinct classical trajectories. These branches acquire nearly orthogonal microscopic records in the permutation sector, preventing
quantum interferences and ensuring the corresponding histories remain consistent.
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All authors Saúl Pilatowsky-Cameo, Jordan Cotler, Daniel Ranard, C. Jess Riedel
Astrophysics of Galaxies
A High-Mass Size Deficit for Void Galaxies in the Complete SDSS DR7
Olivia Curtis, Bryanne McDonough and Tereasa G. Brainerd
We characterize how environment shapes the sizes, luminosity functions, and mass functions of
galaxies in large-scale underdensities by comparing the NSA catalog of the Sloan Digital Sky Survey Data Release 7 with an identically selected TNG300 sample, both built with the void finding
algorithm VoidFinder, and by assigning a local average underdensity contrast to each
galaxy via a spherical top-hat smoothed density field approximation. Void
galaxies have fainter characteristic magnitudes than their non-void counterparts, and, at fixed
stellar mass,
redshift, and color, NSA void
galaxies with $M_*>10^{11}h^{-1}M_\odot$ are about $11\pm3\%$ more compact than
galaxies in the field, a deficit the TNG300 simulation reproduces. The
galaxies that are responsible for this effect are almost all central and predominantly early type, i.e., the systems that are most likely to grow their outer envelopes via late-time mergers. These trends hold across two
redshift bins to $z\leq0.114$. Crucially, this deficit is not a fixed property of the void sample but a steep function of the underdensity contrast, deepening toward the emptiest interiors and washing out at a typical density, implying that strict density control and sample selection are imperative when conducting environmental dependency studies like these. The same environmental dependence appears in the
stellar mass function, which shifts to lower masses in the deepest voids, and in the close-pair (i.e., the ongoing merger) fraction, which falls toward the emptiest regions. Together, these point to a late-time, merger-driven growth of massive
galaxies that is suppressed in voids, leaving their most massive members structurally distinct today.
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High Energy Physics (Theory)
Cosmological Correlators from Scattering Amplitudes: A Review
Soner Albayrak and Savan Kharel
The
primordial statistics underlying the CMB and large-scale structure are encoded in late-time cosmological correlation functions (constructed from the coefficients of the wavefunction of the universe). They are the closest analogue cosmology has to an $S$-
matrix, yet the standard $S$-
matrix toolkit does not directly apply. This review explains how the modern scattering-amplitudes program (spinor helicity, on-shell recursion, the double copy, positive geometry, and generalized unitarity) has nevertheless been extended to cosmology and, through a single analytic continuation, to Euclidean anti-de Sitter space, where the same objects appear as
holographic boundary correlators and are often cleanest to compute. The organizing framework is momentum space on the late-time boundary, where the
primordial statistics are simplest and where the total energy of the external legs, the sum of their momentum magnitudes, controls the analytic structure. At the total-energy singularity, the flat-space scattering amplitude emerges. We develop this toolkit starting from the wave equation and use it to compute tree-level scalar, gauge-field, and graviton correlators, exposing relations across
spins and dimensions. We then show how bulk integrals can be bypassed using cosmological polytopes, on-shell recursion, and curved-space versions of the double copy, before extending the discussion to loops, soft limits, transition amplitudes, and (A)dS cutting rules. Finally, we connect these structures to inflationary observables and to three allied programs: the cosmological optical
theorem, the cosmological bootstrap, and the cosmological
collider. We conclude with a map of the current frontier and a set of open and interesting problems.
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Quantum Physics
Theory of post-selected entanglement transitions in monitored bosons
Ilia Komissarov, Emanuele G. Dalla Torre and Ahana Chakraborty
Entanglement phase transitions driven by
quantum measurements have emerged as a central paradigm in open
quantum many-body physics. Such phase transitions are well established for systems with finite local
Hilbert-space dimensions, such as
qubits and
fermions, while their realization in bosonic systems with unbounded local occupation numbers remains poorly understood. Even in the absence of interactions, number states of
bosons are intrinsically non-Gaussian, preventing the use of standard correlation-
matrix approaches. To address this problem, we develop a replica-free Keldysh field-theoretic framework that expresses the Renyi
entropy of bosonic systems initialized in on-site Fock states in terms of permanents of
matrices constructed from single-particle Green's functions. Applying this framework to a continuously monitored one-dimensional cross-stitch
lattice conditioned on the no-click trajectory, we uncover a transition from volume-law to logarithmic
entanglement scaling. We show that the transition is controlled by a restructuring of the non-Hermitian spectrum that changes the number of long-lived modes from extensive to finite. In the strongly monitored regime,
bosons dynamically condense into a microscopic number of slowest-decaying modes, producing logarithmic
entanglement scaling, whereas an extensive
manifold of long-lived modes at weak monitoring gives rise to volume-law
entanglement. Our results establish a distinct mechanism for measurement-induced
entanglement transitions in free bosonic systems and provide a computationally efficient diagnostic of the measurement-induced bosonic condensation.
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Quantum Physics
Achieving the limits of automorphism gates
Jin Ming Koh, Shayan Majidy, Aranya Chakraborty et al. (+3 more)
Universal fault-tolerant
quantum computing combines versatile but expensive operations with specialized but cheap ones. Its efficiency depends on how much computation can be pushed onto the cheap operations and on the size of the code needed to do so.
Automorphism gates provide such cheap operations using only physical single-
qubit Clifford gates and
qubit permutations. Yet no general theory characterizes their maximum logical power or the minimum code size needed to attain it. We develop such a theory. For stabilizer codes encoding $k\geq3$ logical
qubits, we show that the largest logical group attainable by
automorphisms is generated by all addressable $S$ and $\mathrm{CX}$ gates, and we construct codes attaining it. While this group contains exponentially fewer gates than the full Clifford group, adding one suitable non-Clifford gate yields universality. We further classify the largest logical groups attainable using
qubit permutations, physical single-
qubit Cliffords, or both across general stabilizer and CSS codes, and derive refined bounds for self-dual CSS subclasses. Achieving the maximum-size logical group through
automorphisms requires $n=\Theta(2^k)$ physical
qubits. By contrast, all addressable diagonal Clifford gates, generated by $S$ and $\mathrm{CZ}$, require only $n=\Theta(k^2)$ physical
qubits when implemented using physical single-
qubit Cliffords alone. Both bounds are tight. This
polynomial qubit cost extends beyond Cliffords to all addressable diagonal gates at any fixed level of the Clifford hierarchy, using physical single-
qubit diagonal gates. Thus, for full addressability, the sharpest physical-
qubit cost divide lies between diagonal and $\mathrm{CX}$-type gates, not between Clifford and non-Clifford gates.
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All authors Jin Ming Koh, Shayan Majidy, Aranya Chakraborty, Anqi Gong, Shi Jie Samuel Tan, Norman Y. Yao
Earth and Planetary Astrophysics
Stellar companions sculpt hot Jupiter formation and spin-orbit evolution
Cheyanne Shariat, Kareem El-Badry, Songhu Wang et al. (+4 more)
Stellar companions can drive hot-Jupiter (HJ) migration and
spin-orbit misalignment, but their role in HJ formation remains uncertain. We construct a homogeneous census of resolved
stellar companions to $147$ northern HJs with measured projected obliquities. We obtain uniform adaptive-optics imaging and combine these observations with
Gaia common proper-motion pairs to identify 8 new companion candidates, bringing the observed companion fraction to $71/147=48\%$. Modeling the full survey selection function yields an intrinsic companion fraction of $62\pm5\%$ for mass ratios $q_\star=0.1$-$1$ and projected separations $s=50$-$50{,}000$~au, roughly 3-4$\times$ enhanced relative to field
stars. Including white-
dwarf companions would increase this fraction further. HJs with resolved companions at $50$-$2{,}000$~au are nearly twice as likely to be misaligned compared to systems without detected companions: $46\%$ compared to $24\%$ ($p=0.009$). The misaligned fraction rises steadily from $5\%$ among the coolest hosts to $80\%$ among the hottest, without a sharp transition at the Kraft Break, while the intrinsic companion fraction remains roughly constant across the temperature range. These trends are consistent with HJs beginning with a broad obliquity distribution, followed by progressively weaker
tidal realignment at higher
stellar temperatures. Contrary to previous work, we find that most
stellar companions in our sample are capable of driving eccentric Kozai-Lidov (EKL) oscillations to the
tidal limit under suitable orbital configurations, making high-eccentricity migration dynamically promising. Taken together, these results indicate that
stellar companions sculpt HJ formation and
spin–orbit architectures.
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All authors Cheyanne Shariat, Kareem El-Badry, Songhu Wang, Xian-Yu Wang, Malena Rice, Jerry W. Xuan, David R. Ciardi
Solar and Stellar Astrophysics
Precise and Accurate Mass and Radius Measurements of Thirty Galactic Metal-Poor Stars in Detached Eclipsing Binaries
D. M. Rowan, K. Z. Stanek, C. S. Kochanek et al. (+4 more)
Detached eclipsing binaries have long served as fundamental
benchmarks for making direct comparisons with
stellar models. By combining the light curve and radial velocity orbit of a detached eclipsing binary, precise masses and radii can be measured for both components. However, catalogs of eclipsing binaries are dominated by
solar-
metallicity stars. Here we characterize fifteen eclipsing binaries selected to have $[\rm{M/H}]\lesssim -0.5$ using TESS photometry,
Gaia XP spectra, large spectroscopic surveys, and
Galactic kinematics. We use three spectrographs, PEPSI on the Large Binocular
Telescope, the Levy spectrograph on the Automated
Planet Finder
telescope, and CHIRON on the SMARTS 1.5m
telescope. We jointly model the light curves and radial velocities and measure the
stellar masses and radii with median fractional uncertainties of < 1%. We use spectral disentangling to extract the spectra of both
stars and model them using the spectral synthesis code Korg. We find three systems with $[\rm{M/H}] < -2.0$, two of which are kinematically consistent with the Milky Way's
halo. J0001+2156 has $[\rm{M/H}]=-2.51$, making it the most metal-poor detached eclipsing binary characterized to date. Eleven of the twelve other systems have $[\rm{M/H}] \lesssim -0.5$ and are split between being highly ($[\alpha/\rm{M}] > 0.25$) and moderately ($[\alpha/\rm{M}] < 0.25$) $\alpha$-enhanced. We compare our measured masses and radii to predictions from theoretical isochrones and estimate the ages of the binaries. We estimate ages with typical uncertainties of $\lesssim 0.5$ Gyr, and three of the binaries have estimated ages greater than 10 Gyr, up to $13.8^{+0.8}_{-0.7}$ Gyr. Finally, we update the empirical relations for
stellar masses and radii on the main sequence using a sample of 621
stars.
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All authors D. M. Rowan, K. Z. Stanek, C. S. Kochanek, Benjamin J. Fulton, Ilya Ilyin, Howard Isaacson, David V. Martin
High Energy Physics (Theory)
Vijay Balasubramanian and Charlie Cummings
We derive an
entropy formula for a recently proposed tensor network model of states in 3D
gravity which satisfy the constraint equations of diffeomorphism invariance, and including the effects of matter. After accounting for the invertibility of the spacetime metric, we argue that this formula matches the
quantum extremal surface formula (for small but finite $G_N$), and is not restricted to time symmetric spacetimes. We derive the result via canonical quantization without relying on path integrals, and discuss an extension to compact bulk subregions.
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