A search is presented for the electroweak production of a top-quark pair in association with a $W$ boson and at least one additional jet known as the $t\overline{t}W{j}_{\mathrm{EW}}$ process. This process has embedded within it a $tW$-scattering vertex, which is probed directly for the first time. The collision data were collected with the ATLAS detector during Run 2 of the LHC and correspond to an integrated luminosity of $140{\mathrm{fb}}^{-1}$ at $\sqrt{s}=13\mathrm{TeV}$. The search uses same-charge pairs of electrons and muons together with jets, of which at least one is $b$-tagged. The properties of the most forward jet relative to the rest of the event are used to discriminate the electroweak $t\overline{t}W{j}_{\mathrm{EW}}$ production process from its strong $t\overline{t}W$ production counterpart. A measured (expected) 95% CL upper limit on the cross section is set at ${\sigma }_{t\overline{t}W{j}_{\mathrm{EW}}}<251\mathrm{fb}$ (230 fb), to be compared with the expected Standard Model (SM) cross section of 47.7 fb. Limits are set on the SM effective field theory (EFT) operators $O_{Ht}$ and $O_{HQ}^{(1)}$, which modify the electroweak couplings of the top quark through contributions to the $tW$-scattering vertex. The interpretation acts as a case study to emphasize the importance of energy-dependent sensitivity, multiprocess, and multioperator EFT contributions.

Typicality arguments for emergent spacetime rely on the Lubkin-Page bounds, which show that generic quantum states have vanishing correlations between subsystems. These bounds assume a tensor-product Hilbert space (a type I von Neumann algebra), but the observable algebras in quantum field theory and quantum gravity are generically type II or type III, raising the question of whether the bounds survive. We prove that they do for all type II von Neumann factors. For the hyperfinite type ${\mathrm{II}}_1$ factor with a tripartite decomposition $R\cong A\otimes B\otimes E$, the mutual information between subsystems $A$ and $B$ vanishes as $O((d_A{d}_B/d_E{)}^2)$ in finite-dimensional approximations, provided $d_A{d}_B\le d_E$ (Theorem 1). For Type ${\mathrm{II}}_{\infty }$ factors, including the gravitational algebras constructed via the crossed-product method by Witten and by Chandrasekaran, Longo, Penington, and Witten, the bound acquires an additional exponential suppression controlled by the Bekenstein-Hawking entropy (Theorem 2). We identify the obstructions to extending the result to type III factors and discuss the open question of whether the commutant of the observable algebra can serve as a natural thermal bath that tightens the bound further.

In this paper, we investigate chiral gravitational wave (GW) signals generated from inflation to reheating, driven by a parity-violating (PV) term coupled to the inflaton, $\dot{\varphi }{\epsilon }^{ijk}{h}_{il}{\partial }_j{h}_k^l$, which naturally arises in PV extensions of teleparallel gravity. During inflation, the PV term reduces the sound horizon for right-handed circularly polarized GWs, and amplifies their power spectra relative to left-handed GWs. At CMB scales, these chiral GWs induce BB as well as nonvanishing EB and TB correlations in the CMB, which are potentially detectable by LiteBIRD. During reheating, subhorizon modes undergo tachyonic instability, leading to fully circularly polarized GWs with enhanced amplitudes, which may be probed by future high-frequency GW experiments, such as resonant cavity. The absence of backreaction effect of enhanced chiral GWs imposes constraints on the energy scale of the PV term, the inflationary potential, and the reheating history. Our findings highlight the potential of multifrequency GW experiments to offer a unique probe of the parity violation and early Universe.

We analyze branch decoherence in inflationary quantum cosmology by computing reduced density matrices and branch-overlap factors for long-wavelength perturbations. The Hartle-Hawking no-boundary state is real in the semiclassical regime and contains both expanding and contracting Wentzel-Kramers-Brillouin (WKB) components, whereas the tunneling state is selected as an outgoing complex WKB branch; expanding-contracting decoherence is therefore central for the former and mainly diagnostic for the latter. Using the influence-functional formalism, we derive the noise kernel for a light spectator environment and evaluate decoherence under horizon-based and effective-field-theory (EFT)-motivated coarse grainings. We then compute the single-mode branch overlap directly from the Bunch-Davies mode functions, obtaining $|{\mathcal{D}}_k(z)|=[z^2/(z^2+1){]}^{1/4}$ in the massless limit and $|{\mathcal{D}}_k(z)|\sim z^{\nu }$ on superhorizon scales for massive fields, where $z\equiv -k\eta$ is the dimensionless wave number with $\eta$ the conformal time. In the massless case the accumulated geometric branch functional is evaluated in closed form, with a leading cutoff-sensitive phase-space term and a universal subleading contribution. The calculation provides an explicit quantitative bridge between quantum-cosmological boundary conditions, inflationary squeezing, and the emergence of effectively classical cosmological histories.

We present a data-driven inverse construction of the dilaton field in a bottom-up AdS/QCD description of heavy vector quarkonia. Instead of adopting an ad hoc analytic ansatz, we use a multilayer perceptron to learn ${\mathrm{\Phi }}^{\prime }(z)$ as a smooth function of the holographic coordinate, with $\mathrm{\Phi }(0)=0$ imposed to ensure ultraviolet consistency. The dilaton and its derivatives obtained by automatic differentiation generate the holographic potential $U(z)$, and the associated Schrödinger-like equation is discretized and diagonalized to extract the low-lying eigenmodes. Masses and decay constants are then evaluated from the eigenvalues and the near-boundary behavior of the bulk-to-boundary modes. Training on PDG data for charmonium and bottomonium yields a nonquadratic dilaton profile that resolves the long-standing difficulty of simultaneously reproducing both the heavy quarkonium spectrum and the monotonic suppression of leptonic decay constants with radial excitation. The combined fit achieves rms deviations of 1.26% (charmonium) and 3.32% (bottomonium). This work establishes neural-network reconstruction as a flexible tool for holographic modeling and provides a basis for future extensions incorporating additional channels, lattice constraints, or finite-temperature backgrounds.

We continue our analysis of quantum corrections in the complex structure moduli space of four-dimensional type IIB/F-theory compactifications with $\mathcal{N}=1$ supersymmetry. We find that limits in the complex structure moduli space of F-theory generically induce a strong backreaction on other sectors of the theory, reflecting the nonfactorization of the field space in genuine $\mathcal{N}=1$ theories at the quantum level. Our focus is on quantum corrections to the Kähler moduli in F-theory on Calabi-Yau fourfolds and proceeds in two independent ways: A detailed analysis of the world sheet theory of candidate effective field theory strings for pure complex structure infinite distance limits reveals a mismatch with expectations based on the classical effective action and points to a quantum obstruction of the limit. Complementary to this, we confirm, in large classes of theories, the existence of significant complex structure dependent quantum corrections to the action of supersymmetric instantons which at tree-level are governed by the Kähler moduli. As the quantum corrections become uncontrolled at large complex structure, they require a coscaling of the Kähler moduli to maintain perturbative control. As a result, the naive, classical effective action does not provide an accurate description of pure large complex structure regimes. We comment on possible implications for string phenomenology, specifically with regard to model building and moduli stabilization.

We analyze quantum obstructions to classical infinite distance limits in four-dimensional string compactifications with $\mathcal{N}=1$ supersymmetry. Such quantum effects signal a severe departure from the perturbative effective action and can be of considerable importance for string model building. Our focus is on the complex structure moduli space of type IIB orientifolds with O7/O3-planes and its F-theory description. In this first part of our analysis, we investigate the behavior of $g_s$ corrections in infinite distance complex structure limits. Our main finding is that, depending on the location of the O7-plane, nonperturbative corrections in $g_s$ can become unsuppressed, thus obstructing a perturbative type IIB description in the corresponding asymptotic region of the field space. In particular, this applies to large complex structure limits. To show this, we study the F-theory description of the type IIB orientifold, in which all pure $g_s$ corrections are encoded in the (classical) geometry of an elliptic Calabi-Yau fourfold. This $g_s$-corrected moduli space is found to differ significantly from the classical moduli space. In extreme cases the classical infinite distance degeneration can be completely removed at the $g_s$-corrected quantum level. The behavior of ${\alpha }^{\prime }$ corrections, as well as implications for string model building, are discussed in a companion paper.

In this paper, we explore the perturbative renormalization and study the classical dynamics of the bumblebee model coupled to quadratic gravity, a theoretical setting that allows the violation of Lorentz symmetry. Such a violation arises from a vector field whose potential is engineered to induce a nonzero vacuum expectation value, thereby leading to the emergence of a preferred direction in spacetime and, consequently, to the spontaneous breaking of Lorentz symmetry. Working in dimensional regularization and expanding the metric around flat space, we compute the one-loop divergent parts of the two-point functions of the bumblebee and graviton fields, with special emphasis on the role of Lorentz violating insertions in internal lines. These results determine the counterterms required to renormalize the gravitational and bumblebee sectors in the presence of a preferred background direction, and make explicit how Lorentz violating interactions feed back into the UV structure of quadratic gravity. On the classical side, we derive the field equations and identify exact solutions supported by bumblebee backgrounds. In particular, we show that the Schwarzschild geometry remains an exact solution for an appropriate bumblebee configuration, even in the presence of nonminimal couplings. We close with a discussion of the operator content suggested by the one-loop structure and of prospective extensions to cosmological and less symmetric backgrounds.

The Hubble tension is one of the most significant challenges in modern cosmology. Developing new approaches to estimate the Hubble constant is therefore crucial, and in this work, we employ a Gaussian process, a fully model-independent method that relies solely on observational data. To determine the Hubble constant, we use not only electromagnetic observations but also include gravitational-wave standard siren data from GWTC3. Our measurements of the Hubble constant are strongly consistent with the SH0ES result, with tensions less than $2\sigma$, indicating no statistically significant discrepancy. This approach quantifies the impact of gravitational-wave data on the determination of the Hubble constant, examines its consistency with electromagnetic measurements, and explores its potential role in addressing the Hubble tension.

The hadrosymmetric twin Higgs (HTH) model provides a natural solution to the little hierarchy problem by incorporating all three generations of quarks in a twin sector. Unlike other twin Higgs scenarios, such as the mirror twin Higgs (MTH), the HTH framework avoids introducing additional light states or radiation and thus remains consistent with stringent bounds on the effective number of relativistic species, $\mathrm{\Delta }{N}_{\mathrm{eff}}$. Its particle content and interactions also make it difficult to probe at colliders, highlighting the importance of cosmological tests. In this work, we study the cosmological implications of the HTH model, focusing on the persistent tensions in the Hubble constant ($H_0$) and the matter clustering amplitude (${\sigma }_8$). Implementing the HTH sector in a Boltzmann code and confronting it with cosmic microwave background (CMB) data and local $H_0$ measurements, we find that the HTH scenario partially reduces the Hubble tension from more than $4\sigma$ to about $2.5\sigma$, while also alleviating the ${\sigma }_8$ discrepancy. These results demonstrate that the HTH framework not only addresses naturalness in particle physics but also offers a viable route to mitigating current cosmological tensions, thereby strengthening the link between fundamental theory and precision cosmology.

In this work, we explore the possibility that the compact object in HESS J1731-347 is a dark-matter-admixed quark star, presenting a new challenge in constraining the equation of state of compact objects. We analyze both single- and two-fluid frameworks while incorporating the latest astrophysical observational constraints. Within this framework, we constrain key dark-matter parameters, namely, the dark-matter self-interaction parameter, particle mass, and Fermi momentum, using the properties of the central compact object in HESS J1731-347. We also analyze the mass profile of HESS J1731-347 within single- and two-fluid frameworks; while both descriptions satisfy the observed mass and radius, the two-fluid approach explicitly separates the quark-matter and dark-matter contributions, illustrating how dark matter modifies the internal mass distribution under the same observational constraints. Our results reveal a clear distinction between the single- and two-fluid descriptions. In the two-fluid model, the maximum mass shows a strong dependence on the dark-matter parameters: it decreases with increasing dark-matter self-interaction strength but increases with increasing dark-matter particle mass. In contrast, the single-fluid model is almost insensitive to the self-interaction parameter, while the maximum mass decreases as the dark-matter particle mass increases. This difference arises because, in the single-fluid picture, the homogeneous mixing of quark matter and dark matter leads to an overall softening of the effective equation of state.

If the dark matter mass exceeds the highest temperature of the thermal bath, then dark matter production is Boltzmann suppressed. This opens new possibilities for dark matter model building. In particular, weakly interacting massive particle models that are experimentally excluded can be revived in this setting; conversely, freeze-in models, which would typically be beyond experimental reach, are potentially discoverable in the Boltzmann suppressed regime. In a recent letter, we highlighted these aspects for the case of electroweak doublet fermion dark matter assuming instantaneous inflationary reheating. Due to its elegance and simplicity, we coin this minimal freeze-in (MFI) dark matter. Here we consider next-to-minimal extensions of MFI dark matter. We present the implications for noninstantaneous reheating, including scenarios beyond the standard picture in which the Universe is initially matter dominated prior to reheating. Furthermore, we explore model variations within the electroweak dark matter scenario. Specifically, we consider fermion dark matter in higher representations of $\mathrm{SU}(2{)}_L$, exploring the current limits and the near-future discovery potential.

Recent studies have shown that quantitative concepts from quantum information theory can play a role in analyzing collider physics, including elucidating new physics. In this paper, we study various quantum information measures including magic, trace distance, and fidelity distance, in generic new physics scenarios modeled by the standard model effective field theory. We argue that such measures can indeed show up differences with respect to the pure standard model, and we compare our results with similar findings for the concurrence discussed previously in the literature. We examine the relative sensitivity of different measures to new physics in two-dimensional bins of the top pair invariant mass and scattering angle, finding that the concurrence, magic, and trace distance each emerge as the best measure in at least some regions of the phase space. This highlights the importance of exploring multiple quantum information measures in the hunt for beyond the standard model physics.

Dark matter communicating with the Standard Model solely via electroweak interactions provides a compelling picture. However, thermal freeze-out of electroweak doublet dark matter is generically strongly excluded by direct detection. We show that $\mathrm{SU}(2{)}_L$ doublet fermion dark matter evades direct detection if its mass exceeds ${10}^{10}\mathrm{GeV}$. If the neutral Dirac fermion is split into a pseudo-Dirac pair (via high dimension operator), this limit can be relaxed to 300 GeV. Provided the dark matter mass is above the reheat temperature of the Universe, the production rate never exceeds the Hubble rate in cases of interest; thus, the dark matter never thermalizes. We apply constraints from direct detection (e.g., LZ) and consider the discovery potential of Darwin. This scenario presents the most minimal model of freeze-in dark matter and is both elegant and highly predictive.

Since its discovery, global polarization of the $\mathrm{\Lambda }$ hyperon in heavy-ion collisions has been firmly established and is widely attributed to the large vorticity generated in the rotating quark-gluon plasma. In contrast, nearly fifty years after the first observation of unexpectedly large transverse $\mathrm{\Lambda }$ polarization in unpolarized hadron collisions, its underlying mechanism remains an open and long-standing puzzle, despite being observed across a broad range of collision systems. Although these two phenomena exhibit notable similarities, they are generally regarded as arising from distinct physical origins. In this work, we propose a direct connection between $\mathrm{\Lambda }$ global polarization in heavy-ion collisions and the long-standing transverse polarization observed in unpolarized collision systems. We demonstrate that the alignment between the $\mathrm{\Lambda }$ production plane and the reaction plane, driven by directed flow, can transfer transverse polarization into the measured global polarization signal. Realistic Monte Carlo simulations of $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=3\mathrm{GeV}$ indicate that this mechanism can generate a sizable global polarization, accounting for approximately $23\%\pm 6\%$ of the magnitude reported by the STAR Collaboration. Our results establish, for the first time, a quantitative link between these two well-known phenomena and have important implications for the interpretation of $\mathrm{\Lambda }$ global polarization measurements in low-energy heavy-ion collisions.

We define a higher-derivative generalization of $\mathcal{N}=1$ and $\mathcal{N}=2$ supersymmetric Maxwell-Chern-Simons theories. In particular, the chosen higher-derivative operator is a polynomial function of the d’Alembertian of arbitrary degree, and it is introduced exclusively in the gauge sector. The main goal is to explicitly compute the one-loop quantum corrections to the superfield effective potential for these theories. This is carried out by means of background field quantization in a higher-derivative $R_{\xi }$ gauge. The effective potential is obtained in closed form and expressed in terms of the roots of polynomial functions.

We investigate conservation laws in the absence of gauge invariance by analyzing interacting scalar theories with a massless scalar field. We construct an infinite tower of charges that arise from the subleading equations of motion at null infinity and are built from specific combinations of asymptotic field coefficients. Interestingly, these expressions are finite from the outset, requiring no holographic renormalization. By carefully analyzing the dynamics at spatial infinity, we show that this tower of surface integrals commutes with the $S$-matrix of the interacting model at tree level. As an application, we demonstrate that the conservation of these charges leads to an infinite set of subleading soft relations, valid at tree level in a cubic interaction with massive scalar fields.

We demonstrate that generic two-dimensional Horndeski theories can arise from the reduction of pure gravities in $d\ge 4$ dimensions, and therefore generic on shell configurations for the two-dimensional metric and scalar field correspond to genuine $d$-dimensional gravitational vacuum solutions. We discuss separately the two-dimensional Horndeski theories which can arise from the reduction of $d$-dimensional generally covariant gravitational actions built only from curvature invariants without covariant derivatives and possessing second-order equations of motion on $2+(d-2)$ warped-product backgrounds. The discussion is subsequently extended to generic $d$-dimensional gravitational actions with this latter property. We establish a Birkhoff theorem for all gravitational theories whose reduction yields an integrable two-dimensional Horndeski theory, in which case static spherically symmetric solutions satisfy $g_{tt}{g}_{rr}=-1$ in Schwarzschild gauge whereby the metric function $g_{tt}=-f$ is determined by an algebraic equation. We therefore propose to refer to all such theories as quasitopological gravities. These results can be used to show in reverse that any $d$-dimensional static spherically symmetric and asymptotically flat spacetime satisfying $g_{tt}{g}_{rr}=-1$ in Schwarzschild gauge with an invertible dependence of $f$ on the Arnowitt-Deser-Misner mass can be reconstructed explicitly as a vacuum solution to a $d$-dimensional gravitational theory. We discuss examples of regular black holes such as the Bardeen spacetime, which could not be obtained from polynomial and nonpolynomial quasitopological gravities involving only curvature invariants without covariant derivatives.

We show that perturbatively small higher-derivative corrections to the Einstein-Hilbert action can lead to order-one modifications of the quasinormal mode spectrum of near-extremal Kerr black holes. The spectrum of such black holes contains zero-damping modes (ZDMs) and damped modes (DMs), with the latter only existing when the ratio $\mu =m/(l+1/2)$ is below a critical value ${\overline{\mu }}_{\mathrm{cr}}\approx 0.744$. Thus, this value represents a “phase boundary” that separates a region with both ZDMs and DMs and a region with only ZDMs. We find that the modes lying close to the phase boundary are very sensitive to modifications of general relativity, as their lifetimes receive corrections inversely proportional to their distance to the boundary. We link this growth of the corrections to a modification of the critical point ${\overline{\mu }}_{\mathrm{cr}}$, which can lead to a change in the number of DMs and produce order-one effects in the spectrum. We show that these large effects can take place in a regime in which the higher-derivative expansion remains under control. We also perform an exact analysis of the modification of the phase boundary for lower $(l,m)$ modes and pinpoint those that are most sensitive to corrections. Our results indicate that spectroscopy of highly rotating black holes is by far the most powerful way to search for new physics in ringdown signals.