Papers

This editorial introduces the topical collection arising from the Lemaitre Conference 2024 - the second in a series of meetings dedicated to the scientific legacy of Georges Lemaitre - held at the Vatican Observatory in Castel Gandolfo, 17-20 June 2024, fifty-seven years after Lemaitre's death and on the eve of the centenary of his foundational 1927 paper on the expanding universe. The nineteen contributions collected here address the most pressing open problems at the interface of cosmology, gravitation, and quantum theory: the Hubble tension and the future of ${\Lambda}$CDM in light of recent DESI data; inflationary cosmology and dark-energy model-building in string theory and supergravity, together with the Swampland constraints that bound them; the observer-dependence of the quantum-cosmological wave function; the removal, or consistent crossing, of spacetime singularities - from the canonical quantization of Lemaitre's own 1933 dust model to string-theoretic pre-Big-Bang bounces and many-body constructions of singularity-free black-hole cores; primordial black holes and their gravitational-wave signatures; the search for a background-independent formulation of quantum gravity and a first-principles account of horizon thermodynamics; and the foundational status of the quantum-to-classical transition in gravitational contexts. A proposal for lunar-based cosmological observations, and a historical reconstruction of the genesis of Lemaitre's primeval-atom hypothesis, complete the collection. A recurring unifying thread was the legacy of Lemaitre himself - who first distinguished coordinate from physical singularities and coined the term "horizon" - whose pioneering vision continues to guide research at the frontier of cosmology and fundamental physics.

Given a superconformal gauge theory at a fixed loop order, BPS states can be studied in two ways — by enumerating cohomology classes of a nilpotent supercharge or by diagonalizing the anomalous dimension matrix. The second one allows for a deeper look at how holographic theories distinguish between operators based on whether they are dual to horizonless geometries or black holes. To this end, we carry out the diagonalization in $\mathrm{U}(N)_k \times \mathrm{U}(N)_{-k}$ ABJM theory with $N$ as a formal parameter. This makes it possible to define trajectories of operators and focus on the fortuitous ones which are characterized by being BPS at only finitely many values of $N$. In contrast to $\mathcal{N} = 4$ Super Yang-Mills, where it has been numerically prohibitive to study more than one of these, ABJM gives us access to 16 such trajectories along with their descendants. We show that they take an especially simple form at large $N$ where they agree with the predictions of integrability. We also show that many of them, as with black holes, can only be dressed by certain types of gravitons and comment on how this exercise in cohomology also has implications for properties of the full operators. Finally, we show that the gap to the first non-BPS state in ABJM theory qualitatively differs from that of $\mathcal{N} = 4$ Super Yang-Mills in the expected way.

Metric-affine gravity provides a natural geometric framework in which spacetime curvature, torsion, and non-metricity are treated as independent degrees of freedom, leading to novel cosmological dynamics beyond General Relativity. A generic consequence of such theories is the emergence of effective interactions among the cosmological fluids, even in the absence of explicit phenomenological couplings. Interestingly, the above happens while the Standard Model of Particle physics remains unmodified. In this work, we investigate interacting cosmological models that arise from metric-affine gravity and analyze their implications for the background evolution of the Universe. We derive the modified continuity equations governing the matter, radiation, and dark-energy components, highlighting the geometric origin of energy exchange in the dark sector. We discuss how these interactions modify the expansion history and can effectively mimic evolving dark-energy behavior. The resulting cosmological scenarios are confronted with the most recent observational data from Type Ia Supernovae (Pantheon+), Cosmic Chronometers, and Baryon Acoustic Oscillations (DESI DR2). Moreover, using model selection criteria, e.g., Akaike Information Criterion, Bayesian Information Criterion and the Bayesian Evidence, we compare the aforementioned models against the standard $\Lambda$CDM model. We find that the proposed framework performs slightly better than $\Lambda CDM$, in the light of the data sets considered here. Our analysis demonstrates that metric-affine-induced interactions constitute a viable and theoretically motivated alternative for the description of the Universe.

We establish a universal approach for studying the semiclassical quantization of both probe M2-branes and fundamental strings in asymptotically AdS$_{4}$ backgrounds. On the field theory side, their partition functions are dual to the vacuum expectation value of half-BPS Wilson loops of a class of three-dimensional $\mathcal{N}\geq 2$ Chern-Simons-matter theories. Utilizing this universal approach we arrive at novel predictions for the semiclassical behaviour of the Wilson loop or upon availability match our results with the previously obtained expressions via supersymmetric localization. We also show that the correct choice of holographic ensemble suggests that the semiclassical quantization of probe M2-branes yields the full perturbative answer in the rank of the gauge group $N$ for the dual Wilson loop. This is a proceedings contribution to the ”Athens Workshop in Theoretical Physics: 10th Anniversary”, held at the National and Kapodistrian University of Athens on December 17-19 2025.

Line operators of 4d $\mathcal{N}=2$ theories of class $\mathcal{S}$ of type $A_{N-1}$ in a half Omega background provide a physical model for $SL_N$ skein algebras. In this paper we extend this correspondence to $GL_N$ skein algebras and prove that the $GL_2$ skein algebra of the punctured torus is isomorphic to the $GL_2$ spherical double affine Hecke algebra ${{\mathbf{S}\ddot{\mathbf{H}}}}^{q,t}_2$. The construction is based on $\mathfrak{q}$-nonabelianization for the $SU(2)$ $\mathcal{N}=2^*$ gauge theory, which realizes the skein algebra as a quantum torus algebra associated with the Seiberg-Witten curve. Different regions of the Coulomb branch yield distinct presentations of ${{\mathbf{S}\ddot{\mathbf{H}}}}^{q,t}_2$. These range from the Macdonald $q$-difference module in Fenchel-Nielsen (weak coupling) charts to cluster-type realizations in Fock-Goncharov (strong coupling) charts. Transitions between these descriptions are governed by the vanilla BPS spectrum of the $\mathcal{N}=2^*$ theory via framed wall-crossing, which provides a unified physical framework for several representations of spherical DAHA.

We establish coefficientwise equality between the refined supersymmetric indices of ABJM theory and the BMN matrix model in the plane-wave limit at every fixed positive Chern-Simons level k. For multi-membrane families with fixed multiplicities, and hence fixed finite ABJM gauge rank, the equality holds as all longitudinal momenta tend to infinity with their pairwise differences fixed. Scalar-dressed equal-flux ABJM monopoles correspond to BMN vacua of fuzzy-sphere membranes: multiplicities count coincident membranes, whereas flux magnitudes give the momentum per membrane along the M-theory circle. At the index level, the associated Higgs residues yield a diagonal-holonomy integral for the ABJM plane-wave contribution, whose monopole-harmonic kernel agrees with the BMN matrix-harmonic kernel up to the finite BMN upper-spin cutoff. At finite momentum, the full index difference splits into the non-plane-wave remainder and the harmonic tail above this cutoff. Increasing k shifts the former to higher fugacity grade without changing the surviving kernel or the cutoff contribution. This gives a coefficientwise, multi-membrane extension of the earlier single-membrane index relation.

Entanglement wedge reconstruction provides the sharpest formulation of bulk locality in AdS/CFT, identifying the entanglement wedge as the largest bulk region reconstructible from a boundary subregion. While this statement is well understood at leading order in the large N expansion through both modular flow and Petz map reconstruction, its extension beyond the semiclassical regime has remained unclear. In this work, we show that quantum error correction provides the natural framework for addressing this problem. At leading order, we reproduce the known leading-order reconstruction formulas, and by employing the twirled Petz map, we obtain a systematic and explicit method for incorporating subleading 1/N corrections. Beyond the leading approximation, we have obtained a bi-local correction controlled by a subleading Petz kernel. Our results establish a controlled approach to bulk reconstruction beyond large N and sharpening the role of quantum error correction in holography. This framework provides a controlled path toward understanding bulk reconstruction in fully quantum gravitational settings.

We study a scalar field nonminimally coupled to metric-affine gravity within actions linear in the affine curvature and containing all independent parity-even and parity-odd terms quadratic in torsion and nonmetricity, including mixed contractions. We also include Nieh-Yan-like derivative couplings between the scalar-field derivative and the four torsion and nonmetricity vectors. We derive the connection, metric, and scalar-field equations and, since the connection equation is algebraic, eliminate the independent connection on the generic nondegenerate branch to obtain an equivalent metric scalar-tensor theory in which the non-Riemannian interactions are encoded in an effective kinetic function. We classify several sectors and find that the pure quadratic nonmetricity and pure quadratic torsion sectors separately leave the Einstein-frame kinetic function unchanged relative to the simplest metric-affine scalar-tensor model, whereas their simultaneous presence, the derivative couplings, and generic mixed torsion-nonmetricity interactions can modify it. In the derivative-coupling sector, projective consistency imposes a relation among the couplings. We then consider polynomial coupling functions and study the resulting canonical field redefinition and Einstein-frame potentials. In particular, we illustrate how derivative and mixed torsion–nonmetricity couplings reshape quadratic and quartic potentials in canonical-field space, and show that a quadratic Jordan-frame potential can be mapped, for a suitable choice of derivative and nonminimal couplings, into a natural-inflation potential after canonical normalization. Finally, we separately impose the cosmological principle, determine the reduced combinations of quadratic couplings and the scalar field hypermomentum, and obtain the corresponding modified cosmological equations in the simplest sectors.

We study the double-copy structure of tree amplitudes of the bosonic null string in the flipped vacuum. We show that its level-one vector correlator supplies the Cachazo-He-Yuan (CHY) kinematic half-integrand of the higher-derivative $(DF)^2$ gauge theory, while distinguished compact momentum-winding sectors generate the complementary Parke-Taylor factor. For factorized level-two states, the same Carrollian world-sheet produces two kinematic half-integrands and hence the symmetric double copy to the six-derivative Weyl-cubed graviton sector. Lattice sectors with common external momenta reproduce the Bern-Carrasco-Johansson (BCJ) ordering relation and the corresponding field-theory Kawai-Lewellen-Tye (KLT) representation. These results provide a direct Carrollian world-sheet origin of the double copy and point toward a current-algebra realization of the emergent color sector compatible with the $O(d,d)$ structure of the compact lattice.

We investigate the scattering of null tensionless strings. Classical null strings, given by the ILST action, give rise to three distinct quantum theories built on different vacua and representations of the underlying 2d Conformal Carroll algebra (CCA) which form the residual gauge symmetries on the null worldsheet. In this paper, we are interested in the quantum theory built out of the so-called "flipped" vacuum which realises the highest weight representation of the 2d CCA. By considering a novel class of vertex operators, intimately connected to the compactified null string, we build scattering amplitudes of the theory. We show that one naturally obtains the Cachazo-He-Yuan (CHY) formulae when one considers scattering of massless states in the null “flipped” string.

We extend the recently proposed truncated Polyakov bootstrap to boundary conformal field theories (BCFTs). The formalism uses the analytic functional framework to find approximate solutions of BCFT crossing. We show that a generic nonperturbative solution can be identified by relating it to a family of deformations around generalized free fields (GFF) with a fixed boundary condition. We show this by tracking the flow of BCFT data from GFF with Neumann boundary condition to that with Dirichlet. The same method is then used for the 3d Ising special transition, using the perturbative Wilson-Fisher description as the deformation to identify it. The BCFT data obtained are in remarkable agreement with existing lattice results where available, and are otherwise new.

Recent developments have established exact bosonization and fermionization with a $\mathbb{Z}_2$ symmetry as dualities through gauging. In this work, we apply fermionic gauging, which realizes generalized Jordan-Wigner transformations, to the Bose-Hubbard (BH) model with a global $U(1)$ symmetry and derive an exact dual description in terms of fermionic composites, built from bosons and fermions. In 1D, this duality generalizes the exact mapping between the extended hard-core BH model and the spinless Fermi-Hubbard model to include soft-core bosons. At low energies, the mapping reduces to the well-known equivalence between the sine-Gordon model and the Thirring model. The oscillation wave vector of the fermionic composite correlation function in the gapless phase is fixed by their density, providing a novel manifestation of Luttinger's theorem. We verify the exact duality using density matrix renormalization group (DMRG) calculations and demonstrate that the gapless phase and the phase transition are governed by the compact boson conformal field theory. Our construction naturally extends to generic bosonic systems and higher dimensions, opening new avenues for studying Bose-Fermi mixtures in optical lattices and other strongly correlated quantum systems.

We provide a novel diffeomorphism-invariant approach to asymptotically safe metric quantum gravity. It is based on physics-informed renormalisation group flows with a renormalisation group kernel that guarantees diffeomorphism invariance at each renormalisation group step. Importantly, it also allows us to control and maintain the relevance counting of operators in metric quantum gravity. The resulting effective action is quantum diffeomorphism-invariant and background-independent. As a first non-trivial application, we compute the Reuter fixed point in a manifestly diffeomorphism-invariant way. This computation is augmented with a detailed discussion of regularisation dependence and a systematic estimate of the errors arising from approximations.

We impose unitarity constraints on two-dimensional field theories whose symmetries form the quantum conformal Bondi-Metzner-Sachs algebra, which combines conformal symmetries with asymptotic symmetries of asymptotically flat spacetimes. Positivity constraints put bounds on the central charge, 0<c<2.053. Positivity of the associated vertex algebra allows only four central charges, c = 1, 3/2, 13/7, 2. Thus, only four candidates for unitary field theories remain. We calculate their spectra of primaries and show that they are compatible with BPS-like and holographic inequalities.

A supergravity solution in the literature is an artifact that cannot be verified without re-deriving it: conventions might not be clearly stated, papers have typos, algebra is tedious. SolutionsX is a Mathematica package that turns an xAct environment, whatever physics it may describe, into a stored, machine-verifiable record: code that replays in a fresh kernel, carries its own verification, and can later be fetched for re-use or extension. The shipped examples are supergravity theories and their solutions, but the scope is anything xAct reaches: abstract tensors, differential forms, spinors in any dimension. We follow one published solution through the entire workflow, benchmark the package's component engine against xAct's, and report on three blind runs of an agentic workflow in which an AI coding agent, given the package and a small toolkit, correctly codified a recent paper in under three hours. A database of such records is useful to researchers today and gives agents worked examples to learn from. The package acts as an internal verifier during the thought process of an agent: a claim is checked in the kernel before it is made.

The spherically symmetric sector of broad classes of $D$-dimensional gravitational theories can be effectively described by general two-dimensional Horndeski theories. Exploiting this correspondence, we study the low-temperature dynamics of near-extremal black hole solutions of the parent theories by deriving a universal near-horizon effective description in terms of Jackiw–Teitelboim (JT) gravity. We explicitly show that the logarithmic quantum correction to the entropy, $S_{\rm JT}=\frac{3}{2}\log \left(T/T_{\rm breakdown} \right)$, previously derived for near-extremal black holes in Einstein gravity coupled to matter from the one-loop exact JT partition function, is universal across all models admitting an effective two-dimensional Horndeski description. We determine the general form of the scale at which this correction becomes dominant, $T_{\rm breakdown}$, in terms of the data of the $D$-dimensional theories. We illustrate our general results with charged black holes in Lovelock gravities and regular black holes in Quasitopological gravities.

Recently, the LUX-ZEPLIN (LZ) collaboration reported the observation of a single dark matter (DM)-nucleus scattering event at a nuclear recoil energy of $248\pm23_{\rm stat}\pm23_{\rm sys}$ keV, corresponding to an exposure of 2.84 tonne-year. The absence of events at lower nuclear recoil energies in the predicted spectrum is naturally explained if the underlying process is inelastic DM-nucleus scattering. Motivated by this, we investigate the singlet-doublet fermion DM model, in which the DM consists of two pseudo-Dirac states: the Majorana nature of the lighter state forbids tree level $Z$-mediated elastic scattering identically, while the same states enable inelastic DM-nucleus scattering via $Z$ exchange, with any residual elastic scattering proceeding only through a suppressed Higgs-mediated channel. We further extend the model with a $Z_2$-even scalar triplet, which is responsible both for generating the pseudo-Dirac splitting and for realizing Majorana neutrino masses via the Type-II seesaw mechanism.

We study the emission of a massless closed-string state in the scattering of two D0-branes using the boundary-state formalism. We compute the corresponding five-point amplitudes for graviton and dilaton emission in bosonic string theory and in type II superstring theory, and analyze their field-theory limit. For nonzero impact parameter, the resulting amplitudes are reproduced by an independent calculation in the worldline formulation of the corresponding low-energy theory.

We construct a $dS_d$ null string in a novel way by lifting the standard tensionless string to $R^{1,d}$. Gauging worldsheet scale symmetry introduces terms in the action breaking translation invariance, but preserving the $dS_d$ symmetry $SO(1,d)$. Choosing a De Sitter symmetric gauge fixing of the scale symmetry yields a $d$ dimensional theory which we show has all the expected properties of $dS_d$ tensionless strings. The action happens to be the intriguing Carrol-Weyl symmetric string action in $R^{1,d}$, now with a clear target space interpretation in $d$ dimensions. That it does not, as recently claimed, represent a ($d+1$)-dimensional string in flat ($d+1$)-dimensional Minkowski space settles an apparent issue with the Carrol-Weyl string model. Furthermore, while there are clear obstacles for similar formulations of tensile strings in (A)dS backgrounds, our new insights are easily modified to the formulation of Anti-De Sitter tensionless strings. That our construction generates a curved geometry purely algebraically may have even wider applications.

We evaluate the variations in the area and the entropy of Kerr-Taub-NUT black holes perturbed by bosonic and fermionic test fields. We demonstrate that the critical frequency for a test field at which the variation of the area vanishes is strictly larger than the superradiance limit for Kerr-Taub-NUT black holes. Therefore both bosonic fields in the relevant range and fermionic fields which do not exhibit superradiant scattering can induce a decrease in the area of a Kerr-Taub-NUT black hole. However, the entropy is not directly proportional to the area for Kerr-Taub-NUT black holes. Only fermionic fields with frequencies below the superradiance limit can induce an entropy decrease. The simultaneous loss of entropy by the black hole and the environment identifies a generic violation of the Generalized Second Law (GSL) for fermionic perturbations that fail to satisfy the Null Energy Condition (NEC). For bosonic perturbations that satisfy the NEC, we evaluate the limiting case, where a nearly extremal black hole is perturbed by a scalar field with frequency slightly above the superradiance limit. Our analysis reveals that the minimum increase in the black hole entropy compensates for the entropy loss of the environment, when one assigns Von Neumann entropy to the test field. The GSL remains valid for perturbations satisfying the NEC.

We determine exact finite-volume spin form factors and two-point correlations for a massive Kramer–Wannier interface in the scaling Ising model, separating ordered and disordered phases. The interface admits two complementary lattice realizations: a self-dual inhomogeneous Ising chain whose continuum limit has a sign-changing Majorana mass profile, and, after exchanging Euclidean space and time, a mixed thermal average amenable to Toeplitz/Fredholm methods. Combining these descriptions, we obtain the exact Neveu-Schwarz-Ramond spin matrix elements and a factorized Fredholm determinant for the interface correlator. Defect TCSA and independent fermionic spin-chain calculations confirm the predicted spectrum and matrix elements.

We compute the large overtone quasinormal frequencies $\omega_n$ of asymptotically AdS black holes with interior near-singularity Kasner epochs. We show that the Kasner exponents can be extracted cleanly from the large $n$ behaviour of the dispersion $\partial \omega_n/\partial k^2$ at $k=0$, where $k$ is a boundary momentum. We show that Kasner transitions, as occur in BKL near-singularity chaos, are audible in the quasinormal frequencies and reveal a map between overtone number $n$ and proper time to the singularity. Our results are obtained using a WKB analysis that isolates non-analytic exponents, determined by the near-singularity spacetime, from non-universal data such as the optical distance from the boundary to the singularity. We check our formulae in several numerical models.

The quantum mechanical problem of a particle in a infinite potential well with slanted walls is studied. The energy eigenvalues are determined by a transcendental equation involving the Airy function of the first kind. Two limiting cases are discussed. Next, the allowed energies are found by graphical and numerical methods. The graphical analysis hints that for large quantum numbers the consecutive energy levels get arbitrarily close together. This asymptotic behavior of the energy spectrum actually holds, as shown by means of an intuitive argument and confirmed by resorting to basic properties of Airy functions. In a sense, Bohr's correspondence principle is more accurately fulfilled than in the cases of the standard particle in a box or the harmonic oscillator. A state is regarded the more confined the less the probability of finding the particle in the classically forbidden region. For some stationary states the confinement degree is calculated and a comparison is made with the harmonic oscillator, for which the ground state is the least confined of all stationary states. In the symmetric case — right and left walls of equal slope — something unexpected happens: beyond a certain critical slope the ground state is no longer the least confined eigenstate. Over and above its interesting physical features, this problem provides students with the opportunity to get acquainted with Airy functions, which do not belong to the standard mathematical repertoire of physics undergraduates.

The relationship between Regge factorization of amplitudes and the Collins-Soper-Sterman factorization of hadronic cross sections is explored. Seeking a unified description of rapidity divergences in high-energy scattering and transverse-momentum-dependent factorization, a connection emerges between the Collins-Soper kernel and the Regge trajectory. This provides a framework for bridging high-energy and low-transverse-momentum resummation and for future extensions of $k_T$-factorization beyond leading-logarithmic accuracy.

Ringdown gravitational waves probe black hole spacetimes via quasinormal modes (QNMs). Recent studies have reported oscillatory features in QNM-filtered waveforms, and have led to conflicting interpretations as to whether they represent a near-horizon "direct wave". Reexamining a particle plunging into a Kerr black hole, we show that the saddle-point approximation underlying the proposed interpretation fails near the horizon. Our exact analysis reveals that every source-induced horizon-mode pole is canceled by an infinite tower of Matsubara zeros, independently of orbital and black-hole parameters. The first four stages of this sequential screening are also confirmed by time-domain numerical integration. Thus, within the near-horizon perturbative framework, source-induced horizon-mode signals do not survive at late times.

A localized Gaussian or Pöschl-Teller bump is widely used to probe the sensitivity of Schwarzschild quasinormal modes, where it is typically added to both the Regge-Wheeler and Zerilli potentials. We show that such an additive prescription is generically incompatible with the Darboux transformation connecting the two parity sectors. The reason is that such a transformation restricts a parity-blind bump to a fixed family of bumps with an unavoidable $r^{-2}$ tail, excluding any Gaussian or Pöschl-Teller profile with arbitrary amplitude, center, or width in the additive prescription. We give the complete classification of Darboux-admissible axial and polar pairs of bumps and propose two consistent scenarios: Darboux generator prescription in which a Gaussian or Pöschl-Teller profile is retained as a generator of the bump pair rather than as the bump itself, and Riccati completion prescription in which a Gaussian or Pöschl-Teller profile is regarded as one of the bump pair and its partner will be solved from the Riccati equation. Our frequency-domain calculations confirm that a finite and spurious axial-polar splitting of quasinormal modes will be produced if the Darboux-consistent scenarios are absent, while the centroid shift of the fundamental mode is nearly unchanged.

Recently, it has been proposed that the classical effective action of bosonic string theory should contain only couplings with an even number of tachyon fields. We employ the T-duality procedure to derive such couplings at order \(\alpha'\) (four-derivative order) for the tachyon and massless fields. We first observe that, through higher-derivative field redefinitions of the tachyon potential term, one can choose a scheme in which, apart from the tachyon potential itself, all remaining couplings involve only covariant derivatives of the tachyon and the massless fields. We then construct a minimal basis of such couplings at four-derivative order, consisting of 14 independent terms. Imposing T-duality reduces this set to 6 nonzero couplings, expressed in terms of two unfixed parameters. One of these parameters is determined by matching to the known effective action in the zero-tachyon limit, while the other is fixed by comparison with the sphere-level S-matrix element of four tachyon vertex operators. This latter comparison also establishes that the coefficient of the \(T^4\) term in the tachyon potential is positive. Remarkably, the tachyon mass term and this quartic term are consistent with a potential of the form \((2/\alpha')(-1+\cos T)\), which implies that the closed string tachyon condenses to the minimum of the potential at \(T=\pi\), thereby generating an Anti-de Sitter spacetime with cosmological constant \(\Lambda =-4/\alpha'\).

The extended nuclear-recoil analysis of LUX-ZEPLIN (LZ) has reported one event compatible with a recoil energy near $248$ keV, motivating endothermic dark-matter scenarios with support at large recoil energy. We study a pseudo-Dirac electroweak-doublet dark-matter model embedded in a five-dimensional Dark-Dimension framework. The Standard Model and the vectorlike electroweak doublets are localized on the visible brane, while dark-number violation is communicated through a neutral bulk state. The resulting mass splitting is exponentially suppressed, $\delta=\delta_{\rm UV}e^{-2\pi MR}$, providing a geometric origin for the few-hundred-keV scale relevant to inelastic scattering. The neutral weak current is dominantly off diagonal, fixing the neutron-scale normalization at $\sigma_{\chi n}^{Z}\simeq1.86\times10^{-39}\,\mathrm{cm^2}$. Using a two-bin Poisson diagnostic of the extended LZ recoil window, we find a shallow minimum near $(m_\chi,\delta)\simeq(1.35~\TeV,366~\keV)$, while the thermally motivated point $(1.1~\TeV,360~\keV)$ lies only $\Delta\chi^2\simeq0.21$ higher. The same benchmark is kinematically inaccessible to light targets but remains open for xenon and tungsten, providing a characteristic multi-target test of the model. For CaWO$_4$ we obtain an integrated tungsten rate of $3.15\times10^{-2}$ events kg$^{-1}$ yr$^{-1}$ in the $95$–$150$ keV interval. These results connect the geometric origin of the pseudo-Dirac splitting with high-recoil direct-detection phenomenology.

We find a new set of four-dimensional $\mathcal{N}=1$ Lagrangian gauge theories that flow in the infrared to $\mathcal{N}=2$ Argyres-Douglas theories of type $(A_1, A_{2n})$, $(A_1, A_{2n+1})$, $(A_1, D_{2n+1})$, and $(A_1, D_{2n+2})$. The new dual theories are given by $SU(2)^n$ quiver gauge theories with a number of gauge-singlet flip fields. This description provides dual theories for the previous $\mathcal{N}=1$ Lagrangian realizations given by $Sp(n)$ or $SU(n+1)$ gauge theories, exchanging the rank and the number of nodes in a quiver diagram.

The recently discovered S301 star, with an orbital period of 8.7 years and eccentricity $e = 0.982$, reaches a pericenter of just $140\,R_{\mathrm{s}}$ — approximately nine times closer than S2's $\sim 1200R_{\mathrm{s}}$ — offering an unprecedented laboratory for testing strong-field gravity. We demonstrate that S301's stellar spin precession provides a novel probe of the PPN parameter $\gamma$, scaling as $(2\gamma_{\mathrm{PPN}} + 1)/3$ relative to general relativity (GR). For maximum projected velocity shifts of $46.1~\mathrm{km\,s^{-1}}$, next-generation spectrographs could constrain $\gamma_{\mathrm{PPN}}$ to $\sim 10\%$ precision. When combined with S301's orbital precession — a substantial $\sim 1.95^\circ$ pericenter advance per orbit (GR prediction), approximately an order of magnitude larger than S2's $\sim 0.2^\circ$, constraining $(2\beta_{\mathrm{PPN}} + 2\gamma_{\mathrm{PPN}} - 1)/3$ — the spin measurement breaks the $\beta$-$\gamma$ degeneracy. A MCMC analysis of projected S2 and S301 observations yields $\sigma_\beta \approx 2.3 \times 10^{-4}$, with the $\gamma$ precision limited by the spin precession measurement to $\sigma_\gamma \approx 0.1$. While the spin precession provides an independent consistency check, its true significance lies in probing gravity at $\phi/c^2 \sim 10^{-4}$ and $v/c \sim 0.08$ — four orders of magnitude stronger than Solar System tests and an order of magnitude stronger than current S-star constraints. This complementary approach opens a new window for testing the PPN framework in the strong-field regime and demonstrates the power of combining multiple stellar probes at the Galactic Center.