We report resolution of a halo of X-ray line emission surrounding the Zero Age Main Sequence (ZAMS) G8.5V star HD 61005 by Chandra ACIS-S. Located only 36.4 pc distant, HD 61005 is young (approx. 100 Myr), x-ray bright (300 times Solar), observed with nearly edge-on geometry, and surrounded by Local Interstellar Medium (LISM) material denser than in the environ of the Sun. HD 61005 is known to harbor large amounts of circumstellar dust in a dense ecliptic plane full of mm-sized particles plus attached, extended wing like structures full of micron sized particles, which are evidence for a strong LISM-dust disk interaction. These properties aided our ability to resolve the 220 au wide astrosphere of HD61005, the first ever observed for a main sequence G-star. The observed x-ray emission morphology is roughly spherical, as expected for an astrospheric structure dominated by the host star. The Chandra spectrum of HD 61005 is a combination of a hard stellar coronal emission (T=8 MK) at Lx = 6 x10e29 erg per sec, plus an extended halo contribution at Lx = 1x10e29 erg per sec dominated by charge exchange (CXE) lines, such as those of OVIII and NeIX. The Chandra CXE x-ray morphology does not track the planar dust morphology but does extend out roughly to where the base of the dust wings begins. We present a toy model of x-ray emission produced by stellar wind (SW)-LISM CXE interactions, similar to the state of the young Sun when it was approximately 100 Myrs old (Guinan and Engle 2007), and transiting through an approximately 1000 times denser part of the interstellar medium (ISM) such as a Giant Molecular Cloud (Stern 2003, Opher and Loeb 2024).

We provide a precise, model- and parametrization-independent dispersive determination of the $f_0(500)$, $ρ(770)$, $f_0(980)$, $f_2(1270)$, $f_0(1370)$, $ρ(1450)$, $f_0(1500)$, and $ρ_3(1690)$ resonance pole parameters. They are obtained from the analytic continuation, by means of continued fractions, of forward dispersion relations, whose input is a recent global dispersive analysis of $ππ$ scattering data. From this dispersive study, we find no indications of other resonant poles below 1.7 GeV. Beyond this energy, we also provide resonance pole parameters from the direct analytic continuation of Global Fits to the three existing incompatible datasets. Depending on the dataset we find poles for the $ρ(1700)$, $f_0(1710)$, $ρ(1900)$, $f_2(1950)$, and $f_0(2020)$ resonances. We also present the Argand diagrams of these Global Fits and illustrate that each resonance does not necessarily have to trace a full circle in the diagram.

The existence of a fundamental zero-point length, $l_0$, a minimal spacetime scale predicted by T-duality in string theory or quantum gravity theories, modifies the entropy associated with the horizon of spacetime. In the cosmological setup, this leads to correction to the Friedmann equations governing the evolution of the Universe. In this paper, we investigate the implications of zero-point length $l_0$-corrected gravity for gravitational baryogenesis and early universe thermodynamics, deriving constraints on $l_0$ from observational baryon asymmetry data. We observe that under the condition of non-equilibrium thermodynamics, $l_0$ generates $\dot{\mathcal{R}}\neq 0$ during radiation epoch, where $\mathcal{R}$ is the Ricci scalar. This yields a baryon asymmetry parameter $η\propto l_0^2 T_D^9/M_{\rm Pl}^7$. The observed baryon asymmetry $η\sim 9.9 \times 10^{-11}$ constrains $l_0 \lesssim 7.1 \times 10^{-33} m$, approximately $440$ times the Planck length. Furthermore, our analysis reveals that the zero-point length correction in the Friedmann equation, effectively slows the expansion rate at high energies, resulting in a modified time-temperature relationship where the Universe maintains higher temperatures for longer time during early epochs compared to standard cosmology. Our results establish zero-point length cosmology as a testable framework connecting quantum gravity to cosmological observables, with implications for early universe thermal history and fundamental length scales.

We present a new technique for computing supersymmetric Wilson loops in the ABJM theory via supersymmetric localization, valid for arbitrary values of the rank of the gauge group $N$ and the Chern-Simons level $k$. The approach relies on an operator representation of the Wilson loops within the Fermi gas formalism in terms of the resolvent of a certain integral operator previously encountered in the computation of the ABJM partition function on the round three-sphere. By deriving a set of nontrivial relations for this resolvent, we obtain exact expressions for the generating functions of Wilson loops in terms of the partition function. For large $k$, these expressions reproduce the weak-coupling expansion of the Wilson loops, and in the large-$N$ limit at fixed $k$ they match previously obtained high-precision numerical results. This analysis also resolves the longstanding discrepancy between numerical data and the semiclassical expression for the $1/6$ BPS Wilson loop.

It is well known that any higher order Markov chain can be associated with a first order Markov chain. In this primarily expository article, we present the first fairly comprehensive analysis of the relationship between higher order and first order Markov chains, together with illustrative examples. Our main objective is to address the central question as posed in the title.

Deep exclusive meson production (DEMP) reactions, such as $p(\vec{e},e'π^+)n$, provide opportunities to study the three-dimensional structure of the nucleon through differential cross section and beam- and target-spin asymmetry measurements. This work aims to probe the onset of the hard/soft factorization regime through the exclusive $p(\vec{e},e'π^+)n$ reaction, as measured in the KaonLT experiment at Jefferson Lab Hall C. A 10.6 GeV longitudinally polarized electron beam was incident on an unpolarized liquid hydrogen target, and the scattered electron and produced meson were detected in two magnetic focusing spectrometers, enabling precision cross section measurements. The cross section ratio $σ_{LT'}/σ_0$ was extracted from the beam-spin asymmetry $A_{LU}$. The $t$-dependence of $σ_{LT'}/σ_0$ was determined at fixed $Q^2$ and $x_B$ over a range of kinematics from $2<Q^2<6$ GeV$^2$ above the resonance region ($W>2$ GeV). Furthermore, these data are combined with recent results from CLAS/CLAS12 to determine the $Q^2$-dependence of $σ_{LT'}/σ_0$ at two ($x_B$, $t$) settings. This was fairly flat, with $Q^2$ not having a measurable effect on the value of $σ_{LT'}/σ_0$ in the range explored. Results are compared to predictions from the generalized parton distribution (GPD) formalism, which relies explicitly on hard/soft factorization, and Regge formalism. The Regge models better predict $σ_{LT'}/σ_0$, which suggests that the factorization regime is not yet reached.

We present the first algorithm for computing class groups and unit groups of arbitrary number fields that provably runs in probabilistic subexponential time, assuming the Extended Riemann Hypothesis (ERH). Previous subexponential algorithms were either restricted to imaginary quadratic fields, or relied on several heuristic assumptions that have long resisted rigorous analysis. The heart of our method is a new general strategy to provably solve a recurring computational problem in number theory (assuming ERH): given an ideal class $[\mathfrak{a}]$ of a number field $K$, sample an ideal $\mathfrak b \in [\mathfrak{a}]$ belonging to a particular family of ideals (e.g., the family of smooth ideals, or near-prime ideals). More precisely, let $\mathcal{S}$ be an arbitrary family of ideals, and $\mathcal{S}_B$ the family of $B$-smooth ideals. We describe an efficient algorithm that samples ideals $\mathfrak b \in [\mathfrak{a}]$ such that $\mathfrak b \in \mathcal{S} \cdot\mathcal{S}_B$ with probability proportional to the density of $\mathcal{S}$ within the set of all ideals. The case where $\mathcal{S}$ is the set of prime ideals yields the family $\mathcal{S}\cdot\mathcal{S}_B$ of near-prime ideals, of particular interest in that it constitutes a dense family of efficiently factorable ideals. The case of smooth ideals $\mathcal{S} = \mathcal{S}_B$ regularly comes up in index-calculus algorithms (notably to compute class groups and unit groups), where it has long constituted a theoretical obstacle overcome only by heuristic arguments.

In recent years, agentic artificial intelligence (AI) systems are becoming increasingly widespread. These systems allow agents to use various tools, such as web browsers, compilers, and more. However, despite their popularity, agentic AI systems also introduce a myriad of security concerns, due to their constant interaction with third-party servers. For example, a malicious adversary can cause data exfiltration by executing prompt injection attacks, as well as other unwarranted behavior. These security concerns have recently motivated researchers to improve the safety and reliability of agentic systems. However, most of the literature on this topic is from the AI standpoint and lacks the system-security perspective and guarantees. In this work, we begin bridging this gap and present an analysis through the lens of classic cybersecurity research. Specifically, motivated by decades of progress in this domain, we identify short- and long-term research problems in agentic AI safety by examining end-to-end security properties of entire systems, rather than standalone AI models running in isolation. Our key goal is to examine where research challenges arise when applying traditional security principles in the context of AI agents and, as a secondary goal, distill these ideas for AI practitioners. Furthermore, we extensively cover 11 case studies of real-world attacks on agentic systems, as well as define a series of new research problems that are specific to this important domain.

This work studies the relationship between parametric amplification (or particle creation), adiabaticity and irreversibility in the non-quasi-static regime of a time-dependent quantum harmonic oscillator (TDHO) that evolves unitarily. We provide analytical results for the evolution of the TDHO valid for any functional value of the frequency, which enables us to monitor the behavior of the thermodynamical magnitudes in the non-quasi-static regime. In the latter, the largest modes of the energy eigenstates commonly undergo a process of spontaneous thermalization, where the concept of temperature naturally arises from the unitary evolution of the oscillator, i.e. without relation to any external source of temperature or thermal bath. As the evolution is unitary, this thermalization process can be reversible, facilitating the monitoring of an unexpected \emph{classical-to-quantum} transition that might entail a quantum violation of the third principle of classical thermodynamics. We adapt the standard definitions of quantum heat and work to account for the change in the populations of the energy levels in the non-quasi-static evolution of the TDHO.

We investigate the construction of exponential families from statistical manifolds, a central problem in information geometry. We prove that every compact statistical manifold admits a singular foliation whose leaves are Hessian manifolds. In particular, any non-flat, compact, orientable 3-dimensional leaf arises as a quotient of an exponential family and has only odd Betti numbers. Our approach is constructive: we explicitly describe the foliation and analyze the geometric and topological properties of its leaves. We show that compact orientable leaves are either finite quotients of flat torus or mapping torus with periodic monodromy. In three dimensions, non-flat leaves admit a co-Kähler structure, which allows us to realize them as explicit exponential families parametrized by a Lorentz cone. These results establish a concrete bridge between abstract statistical manifolds and exponential families, highlighting deep connections between information geometry, differential geometry, and the topology of 3-manifolds.

In 2020 we first described placental contractions, and we have now undertaken a study to characterise them and seek features that might automatically separate them from uterine contractions. We recruited 36 healthy pregnant women to undergo magnetic resonance imaging (MRI) between 29 and 42 weeks of pregnancy in a single-centre, prospective, observational study. Participants had fetal ultrasound to confirm normal growth. Dynamic MRI was acquired for between 15 and 32 minutes using respiratory triggered, multi-slice, single shot, gradient echo, echo planar imaging covering the whole uterus. All participants had a live birth of a healthy baby weighing over the 10th centile for gestational age and none developed any associated conditions of placental dysfunction e.g. pre-eclampsia, or severe maternal or fetal villous malperfusion on placental histopathology. Any visible contractions were recorded for all participants who completed their MRI scan and placental contractions occurred in at least 60% of our healthy pregnant population with a median frequency of approximately 2 per hour, and a median duration of 2.4 minutes. Contractions involving a decrease in placental volume of >10% were classified as either placental or uterine by visual observation. Placental contractions occurred more frequently than uterine contractions (p=0.0061), were associated with a larger increase in the surface area of the uterine wall not covered by the placenta (p=0.0015), placental sphericity (p<0.0001) and longer duration (p=0.0151). All contractions led to an increase in the MRI parameter R2* in the placenta. There was large variation both between participants and between contractions from the same individual, in terms of time course and contractions features, with no apparent change across the gestational age range studied, although the largest fractional volume changes were detected at early gestation.

Lensless imaging enables exceptionally compact fluorescence sensors, advancing applications in \textit{in vivo} imaging and low-cost, point-of-care diagnostics. These sensors require a filter to block the excitation light while passing fluorescent emissions. However, conventional thin-film interference filters are sensitive to angle of incidence (AOI), complicating their use in lensless systems. Here we thoroughly analyze and optimize a technique using a fiber optic plate (FOP) to absorb off-axis light that would bleed through the interference filter while improving image resolution. Through simulations, we show that the numerical aperture (NA) of the FOP drives inherent design tradeoffs: collection efficiency improves rapidly with a higher NA, but at the cost of resolution, increased device thickness, and fluorescence excitation efficiency. To illustrate this, we optimize two optical frontends with full-width at half maximums (FWHMs) of 8.3° and 45.7°. Implementing these designs, we show that angle-insensitivity requires filters on both sides of the FOP, due to scattering. In imaging experiments, the 520-$μ$m-thick high-NA design is 59$\times$ more sensitive to fluorescence while only degrading resolution by 3.2$\times$. Alternatively, the low-NA design is capable of three-color fluorescence imaging with 110-$μ$m resolution at a 1-mm working distance. Overall, we demonstrate a versatile optical frontend that is adaptable to a range of applications using different fluorophores, illumination configurations, and lensless imaging techniques.

In this paper, we consider the Donaldson gauge functional and the twisted Aubin functionals on almost Kähler manifolds. As in Kähler geometry, we generalize the inequality between Aubin functionals.

We theoretically investigate how the injector region design of interband cascade lasers (ICLs) impacts the threshold carrier and current densities. The model combines a polarization-sensitive 8-band $\mathbf{k}\cdot\mathbf{p}$ calculation, electrostatics, and a microscopic calculation of Auger recombination rates. The inelastic carrier-carrier scattering is included to lowest order using quasi-equilibrium Green's functions. It captures the combined effects of charge-carrier redistribution, parasitic absorption, and bias voltage on the Auger recombination rate. We show that heavily doping the electron injector suppresses the dominant multi-hole Auger recombination by reducing the hole population of the recombination quantum wells. This agrees with the experimental observation that the heavy doping reduces threshold currents. Unlike the measurements, however, they do not increase at high doping concentrations in our model, which does not include scattering-mediated carrier escape and/or light absorption. Furthermore, by introducing indium to the conventional $\mathrm{Ga}\mathrm{Sb}$ hole injector wells, we explain the rule of thumb from experiments that raising the hole injector levels does not outperform the doping strategy. Our model provides physical insights for optimizing ICL carrier injectors.

The knockoff filter is a powerful tool for controlled variable selection with false discovery rate (FDR) control. In this paper, we leverage e-values to allow the nominal FDR level to be switched post-hoc, after looking at the data and applying the knockoff procedure. This approach addresses a significant limitation of standard knockoffs: while frequently used in high-dimensional regressions, they often lack power in low-dimensional and sparse signal settings. One of the main reasons for this is that the knockoff filter requires a minimum number of selections that depends strictly on the nominal FDR level. By utilizing e-values, we can increase the nominal level in cases where the original procedure makes no discoveries, or decrease it to improve precision when discoveries are abundant. These improvements come without any costs, meaning the results of our post-hoc procedure are always more informative than those of the original knockoff filter. We extend this methodology to recently proposed derandomized knockoff procedures and demonstrate its utility in variable selection problems relevant to drug development using real clinical trial data.

We present a detailed account of the theoretical progress and the computational strategy that led to the non-perturbative determination of the QCD Equation of State at temperatures up to the electroweak scale reported in [Phys. Rev. Lett. 134, 201904 (2025)]. The two key ingredients that make such a calculation feasible with controlled uncertainties are: (i) the definition of lines of constant physics through the running of a non-perturbatively defined finite-volume coupling across a wide range of energy scales, and (ii) the use of shifted boundary conditions which allow a direct determination of the entropy density thus without the need for a zero-temperature subtraction. Considering the case of QCD with $N_f =3$ massless flavours in the temperature interval between 3 GeV and 165 GeV, we describe the numerical strategy based on integrating in the bare coupling and quark mass, the perturbative improvement of lattice observables, the optimization of numerical simulations, and the continuum extrapolation. Extensive consistency checks, including finite-volume and topological-freezing effects, confirm the robustness of the method. The final results have a relative accuracy of about $1\%$ or better, and the errors are dominated by the statistical fluctuations of the Monte Carlo ensembles. We also compare our non-perturbative results with predictions from standard and hard thermal loop perturbation theory showing that at the level of $\%$-precision contributions beyond those known, including non-perturbative ones due to ultrasoft modes, are relevant up to the highest temperatures explored. The methodological framework is general and readily applicable to QCD with four and five massive quark flavours and to other thermal observables, paving the way for systematic non-perturbative studies of thermal QCD at very high temperatures.

Recent developments in extreme value statistics have established the so-called geometric approach as a powerful modelling tool for multivariate extremes. We tailor these methods to the case of spatial modelling and examine their efficacy at inferring extremal dependence and performing extrapolation. The geometric approach is based around a limit set described by a gauge function, which is a key target for inference. We consider a variety of spatially-parameterised gauge functions and perform inference on them by building on the framework of Wadsworth and Campbell (2024), where extreme radii are modelled via a truncated gamma distribution. We also consider spatial modelling of the angular distribution, for which we propose two candidate models. Estimation of extreme event probabilities is possible by combining draws from the radial and angular models respectively. We compare our method with two other established frameworks for spatial extreme value analysis and show that our approach generally allows for unbiased, albeit more uncertain, inference compared to the more classical models. We illustrate the methodology on a space weather dataset of daily geomagnetic field fluctuations.

This paper presents a block-structured formulation of Operator Inference as a way to learn structured reduced-order models for multiphysics systems. The approach specifies the governing equation structure for each physics component and the structure of the coupling terms. Once the multiphysics structure is specified, the reduced-order model is learned from snapshot data following the nonintrusive Operator Inference methodology. In addition to preserving physical system structure, which in turn permits preservation of system properties such as stability and second-order structure, the block-structured approach has the advantages of reducing the overall dimensionality of the learning problem and admitting tailored regularization for each physics component. The numerical advantages of the block-structured formulation over a monolithic Operator Inference formulation are demonstrated for aeroelastic analysis, which couples aerodynamic and structural models. For the benchmark test case of the AGARD 445.6 wing, block-structured Operator Inference provides an average 20% online prediction speedup over monolithic Operator Inference across subsonic and supersonic flow conditions in both the stable and fluttering parameter regimes while preserving the accuracy achieved with monolithic Operator Inference.

We compute, for any Rényi index $n$, the exact difference between the mutual Rényi informations of a pair of free massless scalars and that of a Maxwell field in $d=4$ dimensions. Using the standard dimensional reduction method in polar coordinates, the problem is mapped to that of a single scalar field in $d=2$ with Dirichlet boundary conditions, which in turn can be conveniently related to the algebra of a chiral current on the full line. This latter identification, which maps algebras on an interval to two-interval algebras, yields exact results that clarify the structure of the long-distance OPE perturbative expansion of the mutual information. We find that this series has a finite radius of convergence only for integer $n>1$, while it becomes only asymptotical for $n=1$ and general non-integer values of $n$.

We describe the action of the infinite-dimensional Lie algebra $W_{1+\infty}$ and its B-type analogue on Schur and Schur Q-functions, respectively, using formal distributions framework. We observe an interesting self-duality property possessed by these compact formulas.

Neutron stars (NSs) are interesting objects capable of reaching densities unattainable on Earth. The properties of matter under these conditions remain a mystery. Exotic matter, including quark matter, may be present in the NS core. In this work, we explore the possible compositions of NS cores, in particular, the possible existence of large quark cores. We use the Relativistic Mean Field (RMF) model with nonlinear terms for the hadron phase and the Nambu-Jona-Lasinio (NJL) model and Mean Field Theory of Quantum Chromodynamics (MFTQCD) for the quark phase. Through Bayesian inference, we obtain different sets of equations: four sets with hybrid equations and one set with only the hadron phase. We impose constraints regarding the properties of nuclear matter, X-ray observational data from NICER, gravitational wave data from the binary neutron star merger GW170817, perturbative QCD (pQCD) calculations, and causality. The MFTQCD allows for a phase transition to quark matter at low densities, just above saturation density, while for the NJL sets, the phase transition occurs above twice the saturation density. As a result, the MFTQCD model predicts the presence of quark matter in the inner core of 1.4 M$_\odot$ NSs, while NJL models suggest a low probability of quark matter in the interior of a 1.4 M$_\odot$ NS. Both models predict the existence of quark matter in 2 M$_\odot$ NSs. The slope of the mass-radius curve has been shown to carry information about the presence of quark matter. In particular, a positive slope at 1.8 M$_\odot$ indicates the presence of non-nucleonic matter. A hybrid star with a stiff quark equation of state could explain a larger radius in more massive stars, such as two solar mass stars, compared to canonical NSs.

We have demonstrated the coherent storage and retrieval of single-photon-level light using the atomic frequency comb protocol in a room temperature rubidium vapour. Velocity-selective optical pumping is used to prepare the comb within the $F=2$ hyperfine ground state of rubidium, with the spacing between peaks coinciding with half the $F = 2 - F =3$ hyperfine splitting of the $5^2$P$_{3/2}$ excited state. Weak coherent states of average photon number $μ_\mathrm{in} = 0.083(5)$ are stored with pre-programmed recall time of $7.5\,$ns with an efficiency of $η_{\textrm{AFC}} = 6.59(5)\,\%$, while two temporally distinct modes have been stored and recalled with $η_{\textrm{AFC}} = 2.6(1)\,\%$, allowing for time-bin qubit storage. Finally, the efficiency is observed to be independent of the input pulse polarisation, paving the way for polarisation qubit storage.

Optically accessible, scalable planar nanofluidic channels are attractive for studying transport and localization under confinement. Two dimensional (2D) materials provide large area, atomically flat interfaces for generating such platforms, yet achieving long range one-dimensional (1D) confinement with top-down nanofabrication remains challenging because it requires reproducible nanoscale feature control over extended distances, high yield, and low nonspecific adsorption of analytes under aqueous conditions. Here we demonstrate that thermally induced wrinkling of exfoliated hexagonal boron nitride (hBN) produces self-assembled, liquid-accessible, channel-like networks through a lithography-free process. By varying flake thickness and substrate choice, we quantify statistical trends in wrinkle density and morphology, thereby establishing a practical fabrication design space. Atomic force microscopy and electron microscopy reveal wrinkle-derived geometries with vertical confinement ranging from <2 nm to >100 nm depending on flake thickness and substrate. We further employ time-sequence optical imaging upon droplet-contact, which together with Raman mapping of the water OH-stretch band and capacitance-gradient mapping (dC/dz) by scanning dielectric microscopy (KPFM-based) measurements, demonstrates liquid infiltration and long-term liquid retention within the wrinkle network for more than 10 h. We finally show a proof-of-concept biomolecule confinement application in which we integrate a graphene overlayer as a background suppression interface, enabling wide-field fluorescence localization of ATTO647N labeled DNA along hBN wrinkle-induced nanochannels. Overall, this work establishes self-assembled hBN wrinkles as a scalable, and optically addressable planar nanofluidic platform for confinement of fluids and biomolecules.

The axion is a hypothetical particle associated with a possible solution to the strong CP problem and is a leading candidate for dark matter. In this paper we investigate the emission of axions by accelerated electrons. We find the emission probability and energy within the WKB approximation for an electron accelerated by an electromagnetic field. As an application, we estimate the number of axions produced by electrons accelerated using two counter-propagating high-intensity lasers and discuss how they would be converted to photons to be detected. We find that, under realistic experimental conditions, competitive model-independent bounds on the coupling between the axion and the electron could be achieved in such an experiment.

The difference-of-convex algorithm (DCA) is a well-established nonlinear programming technique that solves successive convex optimization problems. These sub-problems are obtained from the difference-of-convex~(DC) decompositions of the objective and constraint functions. We investigate the worst-case performance of the unconstrained DCA, with and without boosting, where boosting simply performs an additional step in the direction generated by the usual DCA method. We show that, for certain classes of DC decompositions, the boosted DCA is provably better in the worst-case than the usual DCA. While several numerical studies have reported that boosted DCA outperforms classical DCA, a theoretical explanation for this behavior has, to the best of our knowledge, not been given until now. Our proof technique relies on semidefinite programming (SDP) performance estimation.

We investigate two nitrogen-containing isomers of polycyclic aromatic hydrocarbons (PAHs), quinoline (Q) and isoquinoline (IQ), of composition C$_9$H$_7$N in collisions with 7~keV O$^+$ and 48~keV O$^{6+}$ projectile ions. Employing ion-ion coincidence mass spectrometry, we determine branching ratios for H-loss, C$_2$H$_2$-loss, and HCN-loss dissociation channels of Q$^{2+}$ and IQ$^{2+}$. The overall contribution of HCN-loss is found to be the dominant decay channel. A comparison with the results of a parallel experiment on naphthalene, the simplest PAH, reveals that HCN-loss in both isomers has a higher propensity than the analogous C$_2$H$_2$-loss of naphthalene. The positional identity of the nitrogen atom in the two isomers mainly manifests in many-body fragmentation of their dications. Potential energy surfaces of Q$^{2+}$ and IQ$^{2+}$ are further computed to explore complete fragmentation mechanisms. Parent dications (Q$^{2+}$ and IQ$^{2+}$) are identified to isomerize via seven-membered ring structures prior to elimination of C$_2$H$_2$ and HCN. While prompt dissociation is the primary pathway, the dominant channel of each neutral-loss class also exhibits delayed fragmentation.

Let $S$ be a closed surface of genus $g \geq 2$. We study the cocompact domain of discontinuity $Ω_ρ$ in the Einstein universe $\mathrm{Ein}^{p-1,p}$ defined by Guichard-Wienhard and Kapovich-Leeb-Porti for a class of $p$-Anosov representations $ρ:π_1S \rightarrow \mathrm{SO}_0(p,p+1)$ including Hitchin representations, for $p \geq 3$. The quotient $M_ρ = ρ(π_1S)\backslash Ω_ρ$ is abstractly known to be realizable as a fiber bundle over $S$, with unknown fiber of unique homotopy type $F_ρ$. We explicitly exhibit $M_ρ$ as a smooth $\mathfrak{F}_ρ$-fiber bundle over $S$, determining the diffeomorphism type of $M_ρ$ and the unique homotopy type $F_ρ$. Surprisingly, in many situations the fiber bundle $\mathfrak{F}_ρ \rightarrow M_ρ\rightarrow S$ is trivial.

Extensions of the Standard Model typically contain ``flaton fields" defined as fields with large vacuum expectation values and almost flat potentials where scalar self-coupling is small or vanishes at tree level. Such potentials have been used to drive a secondary inflationary epoch after a primary phase of inflation, in what are called thermal inflation models. Although the primordial, high-scale inflationary epoch can solve the horizon and flatness problems, it does not always resolve difficulties associated with late-time relics produced in extensions of the Standard Model. These relics typically decay too late, injecting entropy and energetic particles that spoil successful predictions like Big Bang Nucleosynthesis. It is here that thermal inflation plays a crucial role: diluting unwanted relics by many orders of magnitude without erasing the baryon asymmetry or the large-scale structure set up by the earlier phase of inflation. The preferred scale for this phenomenon is in the range $10^6-10^8$ GeV if one considers supergravity, but without it, any scale above the EW scale is valid. We investigate a typical form of these potentials and determine what are the conditions for the potentials to develop a barrier such that when the flatons settle to the true minimum, the associated Gravitational Waves can be observed, focusing on first-order phase transitions from spontaneous lepton number breaking.

We derive the phase structure and thermodynamics of ferromagnets consisting of elementary magnets carrying the adjoint representation of $SU(N)$ and coupled through two-body quadratic interactions. Such systems have a continuous $SU(N)$ symmetry as well as a discrete conjugation symmetry. We uncover a rich spectrum of phases and transitions, involving a paramagnetic and two distinct ferromagnetic phases that can coexist as stable and metastable states in different combinations over a range of temperatures. The ferromagnetic phases break $SU(N)$ invariance in various channels, leading to spontaneous magnetization. Interestingly, the conjugation symmetry also breaks over a range of temperatures and group ranks $N$, providing a realization of a spontaneously broken discrete symmetry.

Bosonization describes Fermi surface dynamics in terms of a collective field that lives on a part of phase space. While sensible semiclassically, the challenge of treating such a field quantum mechanically has prevented bosonization from providing as powerful a nonperturbative tool as in one dimension. We show that general Fermi surfaces can be exactly described by a particular $N\to \infty$ limit of a $U(N)_1$ WZW model, with a tower of irrelevant corrections. This matrix-valued description encodes the noncommutative nature of phase space, and its (solvable) strongly coupled dynamics resolves the naive overcounting of degrees of freedom of the collective field without the need to cut the Fermi surface into patches. This approach furthermore provides a quantitative tool to systematically study power-law corrections to Fermi surface dynamics.