Papers

We show that no stabilizer state in a discrete realization of a local quantum field theory can flow in the continuum to the vacuum or to any state that resembles the vacuum at short distances. The argument rests on the fact that the entanglement spectrum is flat for stabilizer states but non-flat for cyclic and separating states in a local QFT as a consequence of the type III$_1$ nature of the von Neumann algebras associated with arbitrary subregions. Our result implies that simulating physically relevant QFT states necessarily requires quantum resources beyond stabilizer states and Clifford operations. We comment on the implications for holography.

Hydrodynamics is a macroscopic theory of long-wavelength dynamics around local thermal equilibrium. We develop attractodynamics, the analogous construction around a far-from-equilibrium attractor. Dynamics near a far-from-equilibrium attractor retains some non-hydrodynamic microscopic information, which attractodynamics systematically organizes. We move towards this general structure by starting in 0+1D, and consider a model for which an anisotropic far-from-equilibrium attractor solution is exactly known. This setting provides a clean benchmark in which the ideal attractodynamic equations and a leading transient residual extension can be compared directly with the full kinetic evolution. The resulting hierarchy gives an improvable description of near-attractor dynamics: the ideal theory captures evolution close to the attracting manifold, while retaining the leading off-attractor moments extends the regime of agreement until the finite truncation breaks down. This example identifies the ingredients needed for local 3+1D attractodynamics and for macroscopic attractodynamic theories not derived from an underlying kinetic description.

Interactions between dark matter and dark energy can lead to an apparent phantom-crossing behavior that mimics the expansion history preferred by the latest cosmological observations from DESI baryon acoustic oscillations (BAO), Cosmic Microwave Background (CMB), and Type Ia supernovae (SNe Ia) data. In a previous paper [Khoury, Lin, and Trodden 2025 arXiv:2503.16415], we proposed a concrete particle physics realization of this idea, consisting of a strongly coupled dark sector in which a dark axion is coupled to dark baryons. In this paper, we investigate this idea further by comparing its predictions to the latest cosmological data. We implement the dark axion-dark baryon interaction model in a Boltzmann code and confront it with CMB, DESI DR2 BAO, and SNe Ia data. For the CMB+DESI DR2+DES-Dovekie combination, the best-fit model improves the fit relative to $\Lambda$CDM by $\Delta\chi^2=-14.48$. The preferred solution exhibits a non-monotonic dark-matter mass evolution: the mass decreases between matter-radiation equality and recombination, while increasing over the BAO/SNe-sensitive epoch, leading to an apparent phantom crossing in an effective dark-energy description. Interestingly, the same dynamics produces an Early Dark Energy-like energy injection near matter-radiation equality, but in the data-preferred region this component is too small to raise $H_0$ enough to substantially reduce the current tension.

Inspired by Wigner's classification of elementary particles as irreducible unitary representations of a spacetime symmetry group, we ask what group can give rise in this way to the quantum states of a particle dressed with clouds of infrared gauge bosons. We show that the answer is given by standard asymptotic symmetries (such as BMS in the gravitational case), supplemented by the logarithmic symmetries identified in arXiv:2305.05436. A corollary is the factorization of the Hilbert space of a dressed particle as a tensor product of the space of `naked' one-particle states with a Hilbert space of soft gauge bosons. The latter cannot be obtained without logarithmic transformations, which are ultimately responsible for the presence of a crucial Heisenberg central extension.

We study elastic deformations of thin-shell black holes and wormholes in AdS$_3$ gravity. These geometries are sourced by line defects in the dual conformal field theory, and their shape and mass distribution define elastic moduli of the gravitational saddle. We compute the quadratic response of the partition function to these deformations, defining stiffness kernels for both transverse shape fluctuations and inhomogeneous mass-density fluctuations. The computation of the stiffness kernels can be realized as a hyperbolic response to a conformal welding problem which reduces to the universal Schwarzian response in the heavy-shell limit. The stiffness kernels are two-point functions of defect-local operators in CFT: the displacement operator, which measures the response to shape deformations, and a mass-density operator, which measures the response to local changes in the shell density. We compute the spectrum of these operators in the semiclassical limit, in various black hole and wormhole backgrounds. The spectrum can be discrete or continuous depending on the existence of a non-compact direction transverse to the shell in the geometry. We also provide a Lorentzian interpretation for the stiffness kernels using linear response theory and compute the relaxation time scales towards the corresponding transient deformations in the dual holographic CFT. Lastly, we compute the effect of these elastic deformations on black hole microstate statistics and black hole entropy.

We present saddle-points of the Euclidean Gravitational Path Integral (GPI) corresponding to the supersymmetric index of the D1-D5-P black string. These saddles are complex, supersymmetric, non-extremal solutions of 10-dimensional IIB supergravity theory with arbitrary inverse temperature $\beta$. The solutions carry fixed monopole charges $Q_1$, $Q_5$, $Q_n$, and angular momentum $J_L$ equal to the extremal supersymmetric black string. Crucially, the solutions have fixed angular velocity $\Omega_{R} = - 2 \pi i /\beta$, which is the chemical potential dual to $J_R$. This implements the insertion of $(-1)^{F}$ in the GPI. The Gibbons-Hawking on-shell action is temperature-independent and agrees with the supersymmetric index of the extremal black string carrying the same monopole charges. Upon taking a finite-temperature near-horizon decoupling limit, we obtain solutions of the form $S^3$ fibered over BTZ. Although these near-horizon solutions have finite holomorphic and anti-holomorphic modular parameters, their on-shell action reproduces the Cardy formula of the holomorphic elliptic genus of the dual D1-D5 SCFT$_2$.

We investigate the dynamics of vector excitations localized on cosmic strings in the Abelian-Higgs model. These confined gauge field fluctuations behave as massive vector degrees of freedom propagating along the string. We show that they remain bounded for all values of the scalar self coupling $\lambda$, including parameter regimes in which the previously studied conventional shape mode is no longer present. After determining their spectra and spatial profiles, we analyze their decay through nonlinear coupling to bulk radiation. Their amplitudes exhibit the characteristic power law relaxation associated with non-linear radiation. For sufficiently large $\lambda$ the scalar radiation channel becomes kinematically inaccessible and the decay is instead mediated by quasinormal modes which can be interpreted as Feshbach resonances of the string. We then study the full $3+1$ dimensional dynamics of the vector-excited string. Field theory simulations reveal a parametric instability between the vector mode and the Goldstone sector. In contrast to the shape mode, the vector mode resonantly excites both transverse directions simultaneously. In addition, we build an effective model that captures the instability and identifies the nonlinear couplings responsible for it. Our results show that vector excitations constitute a long-lived massive degree of freedom with a non-trivial role in the dynamics of local strings.

While quantum computers promise to solve classically intractable problems, identifying the point at which fault-tolerant quantum computation outperforms the best classical algorithms for practical applications remains an outstanding challenge. Here we establish a concrete quantum-classical crossover for quantum many-body dynamics under realistic hardware conditions. We introduce a scalable fault-tolerant framework that combines coherent observable estimation with a space-time-efficient implementation of non-Clifford rotations, suppressing the residual logical errors that limit existing partially fault-tolerant approaches. A benchmark against state-of-the-art tensor-network and variational Monte Carlo algorithms reveals a concrete crossover for mixed-field Ising dynamics at modest system sizes. For a physical error rate of $p=10^{-3}$, fault-tolerant simulation requires approximately 2 hours and $3.7 \times 10^5$ physical qubits for a 100-site 1D system, whereas tensor network approaches would require about 100 years. For 2D models, where rapid entanglement growth limits the classical evolution time, we project quantum runtimes within minutes. A physical error rate of $p=10^{-4}$ leads to at least an order of magnitude reduction in qubit count ($3.1 \times 10^4$ physical qubits) and runtime (minutes for 1D and seconds for 2D). The reduction in quantum runtime arises from our improved rotation-state injection and co-design of quantum error correction and observable-estimation protocols, which jointly suppress logical-error accumulation and reduce sampling overhead. Our results establish a scalable route towards practical quantum advantage and identify quantitative engineering targets for future fault-tolerant architectures.

We introduce combinatorial holographic quantum secret sharing (CHQSS) for a bulk subregion in AdS$_3$/CFT$_2$ to study how logical information of the bulk subregion is encoded in the boundary and protected from erasures of boundary subregions. We introduce a distance, a reconstruction threshold, and a secret threshold to characterize CHQSS schemes. We present the phase transitions of multipartite entanglement wedges in a symmetric setup and observe multiple distinct phase transition points. The distance and thresholds depend on the holographic phase and the choice of bulk subregion. We derive the maximum distance. Moreover, we derive the relations between the distance and the thresholds. We construct a family of CHQSS schemes in the symmetric setting that includes perfect threshold CHQSS and perfect non-threshold CHQSS.

We discuss a class of symmetry structures in general spacetime dimension that arise when gauging symmetries in theories with a cubic 't Hooft anomaly. The anomaly mixes two Abelian discrete symmetries $A$ and $B$ with a characteristic class for an additional symmetry $C$, and we gauge $A\times B$. The novelty of this construction is that the resulting symmetry structure involves certain condensation defects of the dual symmetry $\widehat{A}\times\widehat{B}$. Specifically, these defects generate an invertible symmetry that extends $C$, either as an ordinary group extension or as a higher-group, depending on the characteristic class. We describe the corresponding charged operators and states, and illustrate the mechanism in several examples.

This work explores whether localized electromagnetic interactions can be modeled by a physically concluded object-relative ultraviolet weighting of photon modes. The proposal is motivated heuristically by a weak-field self-backreaction estimate for localized energy-carrying modes and by a three-dimensional overlap argument. In the resulting ansatz, the infrared sector remains unchanged up to a characteristic angular wavenumber k_c, while ultraviolet contributions are suppressed asymptotically by a factor of order k_c^3/k^3. The mode structure is object-relative: a real photon is weighted by its frequency u k in the rest frame of the interaction object with four-velocity u. The occupation of the modes and the amplitudes of the vacuum fluctuations, in contrast, follow the rules of special relativity, so that virtual photons in loops are weighted by the invariant k k, i.e. by the Euclidean photon momentum. The weighting applies to photon lines only; applied in the same way to the electron line, it conflicts with gauge invariance or with the measured running of the fine-structure constant. One-loop diagrams with internal photon lines become ultraviolet finite, and the weighting can be represented by a gauge-invariant kinetic term of the photon field, so that the Ward-Takahashi identities are preserved. Four test cases are discussed. A Bethe-type estimate of the Lamb shift places the characteristic scale near the electron Compton wavenumber. The anomalous magnetic moment and the relativistic part of the Lamb shift show, however, that a photon weighting at this scale requires additional structure on the electron line to remain compatible with high-precision measurements. This structure, the vacuum polarization, and the spectral consistency of the weighting define the tasks for future work.

We describe recent advances in our understanding of the analytic structure of Feynman integrals. In particular, we describe two new classes of constraints on such integrals, that identify discontinuities that either cannot be repeated, or that always give rise to the same result (no matter which other discontinuities are computed first). These new constraints hold at all orders in dimensional regularization, and provide us with new input for the Landau bootstrap, where information about the singularities and discontinuities of individual Feynman integrals is used to construct their functional form.

We continue our study of quantum dynamics on a Lie group $G$, initiated in arXiv:2512.19840, by building the path integral that governs transition amplitudes in the Hilbert space $L^2(G)$. This relies on the proper handling of both a noncommutative momentum space and the presence of compact directions in $G$. We show that compactness can be handled through a sum over winding numbers in maximal tori of $G$, generalizing the similar sum commonly encountered for path integrals on a circle. As applications, we compute semiclassical approximations of propagators and partition functions of Euler-Arnold systems, up to (and including) two-loop order.

Unlike the gravitational waves classically generated by moving macroscopic masses, the diffuse backgrounds of gravitons originate most likely from zero-point fluctuations of the gravitational field amplified by the evolution of the space-time curvature. The resulting entangled states lead to specific second-order correlation effects that could be eventually detected. For a quantitative analysis of this empirical expectation we scrutinize the interactions between the cosmic gravitons and the fundamental mode of a quantized electromagnetic field confined inside a closed optical resonator with perfectly-reflecting walls. We show that the Hanbury-Brown Twiss correlations of the photons are insensitive to the degrees of second-order coherence of the gravitons even barring for the exceedingly small couplings of the problem. Since the degree of second-order coherence of the photons does not reflect the correlation properties of the gravitons, the statistical properties of the gravitons (and their super-Poissonian statistics) cannot be inferred, even in principle, from the intensity correlations of the cavity modes.

Using the $C-$metric in the context of $F(R)$ gravity coupled with the ModMax nonlinear electromagnetic field (the $F(R)-$ModMax theory), we derive an exact black hole solution in a four-dimensional spacetime. We then examine how various parameters influence the behavior of accelerating ModMax black holes. Treating this black hole as a thermodynamic system, we calculate the Hawking temperature and entropy for the accelerating ModMax black holes within the framework of $F(R)$ gravity. Subsequently, we explore the impact of the parameters in $F(R)-$ModMax theory on the Hawking temperature and entropy. We also assess local stability by analyzing the heat capacity. Additionally, we investigate both the angular shadow and the shadow radius of an accelerating black hole in the context of $F(R)-$ModMax gravity.

We compute the heterotic moduli-space metric through $\alpha'^2$ for backgrounds admitting a smooth $\alpha'\to0$ limit. The Kaehler potential is unchanged when written in an appropriate field basis suggested by the ten-dimensional supersymmetry equations, while the metric receives $\alpha'^2$ corrections. We discuss this and clarify the roles of the extension bundle, F-terms, the D-terms and the string-derived moduli space metric.

In this paper, we construct a family of solutions to the $3$-fold Hull-Strominger system using the Aeppli class, without introducing the auxiliary gauge connection on the tangent bundle. In particular, we deform the conformally balanced metric along an Aeppli class off-shell and then tune it by a hermitian $(1,1)$-form dependent on this Aeppli class on-shell to satisfy the anomaly cancellation condition. The existence of the family of solutions is then obtained by the implicit function theorem. This refines the previous work by not introducing auxiliary gauge connection, thereby matching the expected dimension with the Bott-Chern parameter. This construction of the Aeppli parameter also extends to the $n$-fold Hull-Strominger system.

We revisit the renormalization group (RG) approach to the one-dimensional stochastic Kuramoto-Sivashinsky (KS) equation and show that previous approaches based on perturbative Wilsonian RG with a sharp cutoff are not valid, even though they yield a qualitatively correct picture. The reason is that taking momentum derivatives while using the sharp cutoff is not well-defined in some cases and leads to intrinsic divergencies. This is a well-known problem of Wilsonian RG, which can be simply cured by using a smooth cutoff, and employing the functional renormalization group (FRG) framework. We establish the flow equations for the KS model within the FRG, and demonstrate that it flows to the Kardar-Parisi-Zhang (KPZ) fixed point at large scales. We then calculate the full two-point correlation function over a wide range of momenta and frequencies. We show that it exhibits three universal scaling regimes that we characterize: the KPZ regime (with dynamical exponent $z=3/2$), the Edwards-Wilkinson regime (with $z=2$) and the recently discovered inviscid regime (with $z=1$). The latter develops over an extended range of large wavenumbers and originates from the vanishing of the effective viscosity. Lastly, we investigate the large-scale behavior of the deterministic KS equation by studying the limit of vanishing noise and we determine the scales where the KPZ regime can emerge in the deterministic case.

We investigate the behavior of Einstein crystals in noncommutative backgrounds described by the Snyder and Snyder-de Sitter models. Possible novel effects, which may arise in realistic systems such as diamond crystals, are analyzed within a thermodynamical framework. We show that noncommutativity influences the key thermodynamic quantities, including internal energy and specific heat. These corrections can be directly related to modifications of the underlying uncertainty relations, of the generalized uncertainty principle (GUP) and generalized extended uncertainty principle (GEUP) types.

We develop a comprehensive relativistic framework for geometrically thin, optically thick Shakura–Sunyaev $\alpha$-viscous accretion disks around rotating Hayward regular black holes embedded in a quintessence dark energy (DE) field. The static, spherically symmetric building blocks of our spacetime are each exact solutions of the Einstein field equations, sourced respectively by the Hayward non-linear electromagnetic field and a quintessence fluid with equation-of-state parameter $\omega<-1/3$; we combine and rotate them following standard practice for this class of models, and we are explicit throughout about the resulting metric's phenomenological status. Abandoning the stress-free inner boundary of the Novikov–Thorne–Page (NTP) model, we analytically incorporate a non-zero viscous torque $\Tcal_{\rm in}$ at the innermost stable circular orbit (ISCO) via the relativistic vertical epicyclic frequency $\Obot(r)$. We prove that the bolometric efficiency $\eta=[1-E(\rISCO)]\times100\,\%$ is strictly independent of the viscosity parameter $\alpha$ but sensitive to both the Hayward length scale $l$ and the DE density $\rho_0$, establishing a rigorous two-observable degeneracy-breaking strategy. At benchmark parameters ($j=0.4$, $l=0.5M_{\BH}$, $\rho_0=2\times10^{-4}$), the combined geometry yields $\eta=8.71\,\%$, substantially above the vacuum Kerr value $7.51\,\%$ at the same spin. The viscosity correction $\delta\Fcal/\Fcal_{\rm NTP}$ diverges at $r\to\rISCO^+$, amplified by the geometric odification of the boundary pressure: the viscosity amplification ratio rises from $0.80$–$4.52\,\%$ (vacuum Kerr) to $0.87$–$6.76\,\%$ (Hayward+DE) at $\alpha=0.1$, providing a clean, monotonic observational discriminator accessible to NICER and NuSTAR, independent of the bulk spectral normalisation.

We investigate the dynamical symmetry of the Sasaki-Mukhanov equation, which governs the evolution of primordial perturbations during inflation. By mapping the Sasaki-Mukhanov equation to a constant-frequency harmonic oscillator via an auxiliary Ermakov field satisfying the Ermakov-Pinney equation, we construct the associated $sl(2, R)$ generators and derive the Ermakov-Lewis invariant. We apply this framework to de Sitter space and slow-roll inflation, demonstrating that the Bunch-Davies vacuum gives $I_{EL} = 1/2$, conserved non-perturbatively at all orders in slow-roll.

We present the scattering modes of the oscillon, to the first three orders in the Fodor expansion, in terms of elementary functions. In the case of relativistic modes, these results are new. We use them to fully decompose the field and also to analytically invert the decomposition. In quantum field theory, this allows us to show that the corresponding creation and annihilation operators satisfy the usual oscillator algebra, extending to relativistic modes the demonstration that, at a fixed order in the Fodor expansion, a periodic oscillon state exists.

Testing Lorentz invariance violation (LIV) is notoriously difficult, as its characteristic energy scale, $M_\star$, in modified dispersion relations typically lies beyond current experimental reach. To enable a low-energy probe, we investigate the quantum coherence of an inertial Unruh-DeWitt (UDW) detector interacting with a massless scalar field with a Lorentz-violating dispersion relation $\omega_{|\textbf{k}|}=|\textbf{k}|f(|\textbf{k}|/M_\star)$. Unlike the Lorentz-invariant case where quantum coherence is rapidity-independent, we find for the Lorentz-violating quantum field case the dynamics of detector's quantum coherence exhibits a strong dependence on its rapidity – offering a potential low-energy signature of LIV. Applying this to the polymer-quantized scalar field theory inspired by loop quantum gravity, we show that the detector's quantum coherence exhibits a pronounced dependence on rapidity and undergoes a sharp transition near a critical rapidity $\beta_c \approx 1.3675$, a value within reach of existing facilities like the Relativistic Heavy Ion Collider. We also show how the detector's rapidity and its energy-level spacing enhance the response to the test of LIV. Our results establish quantum coherence as a sensitive and practical probe of LIV, providing a complementary avenue for testing quantum gravity-induced modifications to field theory.

We study accretion and thermal diagnostics motivated by neutrino processes for a static black hole reconstructed from a three-parameter generalized entropy. The construction is thermodynamic by design: the entropy deformation is not mapped to a radial-coordinate redefinition or to a prescribed Reissner–Nordström-like correction. Instead, the generalized entropy fixes the horizon response factor $\Xi_h=dS_G/dS|_{S_h}$. The effective exterior geometry is then reconstructed by requiring its surface-gravity temperature to reproduce the generalized thermodynamic temperature. As a result, the metric preserves the horizon area and the Schwarzschild asymptotics, and reduces smoothly to Schwarzschild when $\Xi_h\to1$. The entropy response is encoded in $\lambda_G=1/\Xi_{\rm h}-1$, whereas the exterior radial dependence requires an additional localization prescription. The detailed accretion analysis is performed for the power-law family $h(x)=x^{-p}$, with $p\geq2$. Within this reconstruction family, positive $\lambda_G$ moves the photon sphere and ISCO inward, decreases the critical shadow scale, raises the radiative efficiency, and concentrates the energy release toward the inner disk, while negative $\lambda_G$ produces the opposite trend. A complementary comparison with exponential and rational localization functions shows that this qualitative ordering is preserved for the profiles tested, although the magnitude of the strong-field shifts remains profile-dependent. Finally, the neutrino-motivated thermal sector ...

Massive gravity is one of the most natural proposals for modifying gravity at large distance scales. First proposed to tackle the cosmological constant problem, it has the potential to simultaneously maintain theoretical consistency and agreement with current observational constraints. The development of Lorentz-invariant ghost-free massive gravity resolves long-standing obstacles associated with interacting massive spin–2 fields. Central to this development is a highly constrained nonlinear interaction structure that propagates exactly five degrees of freedom. The same interaction structure raises the strong-coupling scale to its maximal value, which organizes the theory as an effective field theory. Phenomenological consistency with local tests of gravity is ensured by nonlinear screening through the Vainshtein mechanism, which is automatically built in. Recent developments have shown how to formulate the theory in a manifestly well-posed way within some limits and beyond. From an effective field theory perspective, unitarity, analyticity, and causality impose powerful constraints that strongly single out the ghost-free theory as a distinguished infrared realisation of massive gravity. We further discuss these results in light of recent consistency analyses, which we put in context. Interestingly, massive gravity has recently been invoked in discussions of black-hole entanglement entropy and spacetime regions known as `islands'. The theory is also shown to emerge as an exactly solvable $T \bar T$ deformation in both two dimensions and for special cases in higher dimensions, opening up valuable insights into its UV behaviour. Massive Gravity thus serves as a valuable theoretical laboratory for exploring the interplay between phenomenology and UV completions in infrared modifications of General Relativity.

We present a partial classification of four-dimensional, non-supersymmetric Type II toroidal orbifolds with non-abelian point groups of rotations, and vanishing vacuum energy at one loop in string perturbation theory. The classification is complete within a class of such orbifolds with the restriction that the point group only acts on a $T^5$ inside the full internal $T^6$. By studying their decompactification limits along the leftover $S^1$, we see that the 17 solutions we find can alternatively be obtained as Scherk–Schwarz compactifications of some parent asymmetric orbifold. Along the way, to ensure the absence of anomalies, we compute bordism groups $\Omega_3^{Spin(BG)}$ for a variety of non-abelian crystallographic groups $G$.

The microscopic description of extremal supersymmetric black holes in AdS$_2$/CFT$_1$ holography has remained elusive despite recent progress in the statistical description of near-extremal black hole physics. In this work we revisit Denef's quiver mechanics description of D-brane bound states in the Coulomb branch, which displays an emergent conformal symmetry in the AdS$_2$ scaling limit. This conformal symmetry is however broken by superpotential corrections near the locus where the Coulomb and Higgs branches meet, and its significance has so far remained unclear. In order to to clarify this issue, we derive and interpret a fixed-point formula for the superconformal quiver index using localization techniques. Focusing on cyclic abelian quivers, we show that, in a certain large-$N$ limit (with the rank $N$ of the quiver gauge group), the fixed points are located in the regime where the conformal description is reliable. In this limit, our expression for the superconformal index precisely captures a contribution to the microscopic scaling BPS index derived by Beaujard, Mondal and Pioline, which was hitherto not visible on the Coulomb branch. Our results are hoped to provide a step towards a stringy realization of AdS$_2$/CFT$_1$ duality.

Large-scale structure provides a powerful probe of inflationary physics through primordial non-Gaussianity (PNG): the galaxy power spectrum depends on local PNG through scale-dependent bias, while the galaxy bispectrum depends sensitively on both equilateral and orthogonal PNG. In this paper, we study whether galaxy surveys can also probe folded PNG, whose shape is enhanced near $k_1+k_2-k_3\rightarrow0$. We consider three inflationary models with folded PNG, including excited initial states, imaginary speeds of sound, and dissipative inflation. These models fall into two classes: cutoff-regulated cases in which the folded-enhanced region has a power-law width, and dissipation-regulated cases in which the enhanced region is exponentially narrow. We develop a numerical pipeline for computing the corresponding PNG contributions to the redshift-space galaxy power spectrum multipoles and bispectrum monopole within the EFTofLSS. Using Fisher forecasts, we show that most of the constraining power on folded PNG comes from the galaxy bispectrum. For the cutoff-regulated models, nuisance parameter marginalization causes only a mild loss of information at large folded enhancement, but finite Fourier-space binning degrades constraints once the folded region becomes narrower than the bin width. For the dissipation-regulated models, the exponentially narrow folded enhancement is hard to resolve and the observable signal instead comes from the broader support of the template, leading to weaker binning dependence but larger overlap with the equilateral template. Our results show that folded PNG is a distinctive and promising target for galaxy bispectrum analyses, and the detectability depends on the width and morphology of the folded enhancement. The numerical pipeline developed in this work is general and can be used to study a wide class of non-separable primordial bispectra.

The worldsheet description of string amplitudes can be reinterpreted as a baby universe field theory. Under this reinterpretation, we determine the $\alpha$-states of a topological string theory: the Hurwitz worldsheet. We find that their relation to the Hartle–Hawking state encodes foundational results in the asymptotic representation theory of the symmetric group. In the holographic dual, our results characterize the pseudorandom nature of an ensemble of cluster-decomposing correlators.

Collisions of ultra-relativistic bubbles during cosmological phase transitions can produce particles much heavier than the transition scale. Previous analyses modelled this process as the off-shell decay of the scalar background. We show that its results parametrically overestimate hard particle production and depend on the gauge choice and the coordinate choice in field space. We propose an alternative formalism, analogous to the partonic description of high-energy collisions. In the ultra-relativistic limit, the colliding bubbles undergo nearly free passage and hard production arises from on-shell scatterings among the quanta constituting the Lorentz-contracted walls. We apply this approach to heavy scalar, fermion, and vector particle production, and study the implications for dark matter, leptogenesis, graviton production and primordial gravitational waves.