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Journal articleBenetti Genolini P, Gaar F, Gauntlett JP, et al., 2026, , Physical Review Letters, Vol: 137, ISSN: 0031-9007
<jats:p> Conformal supergravity provides an effective off-shell formalism to study higher derivative actions. We show that the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>D</a:mi> <a:mo>=</a:mo> <a:mn>4</a:mn> </a:mrow> </a:math> , <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi mathvariant="script">N</c:mi> <c:mo>=</c:mo> <c:mn>2</c:mn> </c:math> theory admits equivariantly closed forms. These may be used to compute closed-form expressions for supersymmetric observables in a general class of supergravity theories with higher derivative couplings, without any need to solve equations of motion. We discuss applications to holography, presenting results for on-shell actions that are conjecturally valid to all orders in the perturbative <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mn>1</f:mn> <f:mo>/</f:mo> <f:mi>N</f:mi> </f:math> expansion. </jats:p>
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Journal articleMoursy TT, Pol NS, Agazie G, et al., 2026, , The Astrophysical Journal, Vol: 1008, Pages: 205-205, ISSN: 0004-637X
<jats:title>Abstract</jats:title> <jats:p> We quantify pulsar timing array (PTA) sensitivity to anisotropy in the gravitational-wave (GW) background using the cross-correlation-based Fisher information matrix in the pixel and spherical harmonic bases. We use a set of simulations to empirically determine scaling relations of a PTA’s sensitivity to anisotropy with the number of pulsars <jats:italic>N</jats:italic> <jats:sub>psr</jats:sub> in the array, the error <jats:italic>δt</jats:italic> on the times of arrival, the frequency <jats:italic>f</jats:italic> <jats:sub>GW</jats:sub> of the GWs, and the angular scale ΔΩ of the anisotropy. The sensitivity scales approximately as <jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">psr</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.8</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> </jats:inline-formula> , <jats:italic>δt</jats:italic> &
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Journal articleHanany A, den Driessche EV, 2026, , Journal of High Energy Physics, Vol: 2026
<jats:title> A <jats:sc>bstract</jats:sc> </jats:title> <jats:p>We compute the Higgs branch chiral ring of a simple class of 5d theories at strong coupling. A deformation by the instanton mass implies that the chiral ring at weak coupling is corrected by a nilpotent operator, the gaugino bilinear. Consequently, F-term equations alone do not suffice to completely determine the moduli space of vacua and perturbative non-renormalization arguments are invalidated.</jats:p>
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Journal articleHanany A, den Driessche EV, 2026, , Journal of High Energy Physics, Vol: 2026
<jats:title> A <jats:sc>bstract</jats:sc> </jats:title> <jats:p> We expand in instanton charge sectors the representation content of the infinite coupling chiral ring of the Higgs branch of 5d = 1 <jats:italic>Sp</jats:italic> ( <jats:italic>k</jats:italic> ) theories with <jats:italic>N</jats:italic> <jats:sub> <jats:italic>f</jats:italic> </jats:sub> flavours. The entire chiral ring can be expressed as the product of bare instantons, one for each topological sector, times a common dressing factor depending on the mesons and the instanton-anti instanton bound state. The dressing factor, which is independent of the instanton number, encodes the chiral ring of the theory at finite coupling with one additional colour. </jats:p>
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Journal articleAlMuhanna H, Evans TS, Vasiliauskaite V, 2026,
Interdisciplinarity revealed by transitive reduction of citation networks
, Scientific Reports, ISSN: 2045-2322 -
Journal articleHallam J, Magueijo J, 2026, , Journal of Cosmology and Astroparticle Physics, Vol: 2026, Pages: 039-039
<jats:title>Abstract</jats:title> <jats:p>Unimodular gravity recasts the cosmological constant as an integration constant, fixed by a constraint on the volume element rather than chosen in the action. We ask what becomes of this constant when matter couples not to the gravitational metric, but to a second metric disformally related to it through a scalar field. Imposing a volume constraint on each metric, we find a theory in which the scalar does not propagate, yet still drives a non-trivial expansion. Written as a single-metric theory, its kinetic term is fixed to a prescribed function of spacetime, and the cosmological constant is replaced by a vacuum contribution that need not be constant. Moreover, we find that this theory admits a phantom crossing through a purely frame-dependent mechanism. This construction, however, rests on a feature invisible with a single metric, and unimodular formalisms that are classically equivalent in that case cease to agree once there are two disformally related metrics.</jats:p>
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Journal articleAlexander S, Alexandre B, Fine M, et al., 2026, , International Journal of Modern Physics D, Vol: 35, Pages: 1-15, ISSN: 0218-2718
Graviweak theory seeks to unify gravity (specifically in its self-dual formulation) with the weak interaction, preying on their parallel chiral (Formula presented) structures. In this paper, we further this idea by folding it with the concept of spontaneous symmetry breaking. We do this first with a standard Higgs field and potential, starting with a unifying parity-invariant theory which splits into the usual gravity and weak sector under spontaneous symmetry breaking. By rewriting the theory in the two-spin framework, we are then prompted to discuss generalizations, within the generic approach known as MacDowell–Mansouri theories where a larger internal gauge group is broken. One of the predictions of the ensuing construction is a nonminimal coupling in the low-energy broken phase between curvature and the weak gauge fields, translating at the quantum level to a direct channel between the graviton and the weak bosons.
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Journal articleAgazie G, Anumarlapudi A, Archibald AM, et al., 2026, , Astrophysical Journal Letters, Vol: 1006, ISSN: 2041-8205
In the published article, we presented inferences about the population of supermassive black hole (SMBH) binaries emitting at nanohertz gravitational-wave (GW) frequencies based on the 15 yr dataset from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). Here, we report two bugs in the astrophysical analysis software used for the published article. While parameter posteriors of our inference can be seen to have slight differences on close inspection, none of the conclusions from the original publication have changed, including the finding that the measured GW background is dominated by the most massive, high-mass-ratio SMBH binaries. Our corrected results show slightly less evidence for environmental interactions with SMBH binaries and indicate that the population of SMBH binaries contributing to the GW background occurs at slightly higher mass ratios and redshifts than indicated in the published article. Correcting these errors does not change the central conclusion that astrophysically motivated models of SMBH binary populations are able to reproduce both the amplitude and shape of the observed low-frequency GW spectrum. These errors did not affect any other analyses of the NANOGrav 15 yr dataset, including the evidence for a GW background presented in another of our published articles.
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Journal articleKallosh R, Tseytlin AA, 2026, , Journal of High Energy Physics, Vol: 2026
We review the structure of superconformal anomalies in 4d N = 4 conformal supergravity (CSG) coupled to a number N<inf>v</inf> of N = 4 vector multiplets and 6d (2,0) CSG coupled to N<inf>T</inf> of (2,0) tensor multiplets. Anomalies cancel if N<inf>v</inf> = 4 and N<inf>T</inf> = 26 respectively. If the CSG part of the action is dropped and N<inf>v</inf> = 6 + n<inf>v</inf>, the first theory is classically equivalent to the 4d N = 4 Poincaré supergravity (PSG) coupled to n<inf>v</inf> vector multiplets, while the second one with N<inf>T</inf> = 5 + n<inf>T</inf> is classically equivalent to the 6d (2,0) PSG coupled to n<inf>T</inf> tensor multiplets. We suggest that these facts imply that divergences in the 4d PSG with n<inf>v</inf> vectors should be proportional to n<inf>v</inf> + 2 and similarly in the 6d PSG with n<inf>T</inf> tensors to n<inf>T</inf> – 21. This conjecture appears to be consistent with most of the known results of explicit scattering amplitude computations in these 4d and 6d PSG theories, apart from one coefficient in the 3-loop mixed vector scattering amplitude computed in arXiv:1305.4876.
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Journal articleGaar F, Gauntlett JP, Park J, et al., 2026, , Physical Review D, Vol: 114, ISSN: 2470-0010
<jats:p> We show how equivariant localization can be used to compute the on shell action for supersymmetric <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>D</a:mi> <a:mo>=</a:mo> <a:mn>5</a:mn> </a:math> anti–de Sitter rotating, charged black holes in theories of supergravity with higher derivatives. An exact match with a dual field theory computation of the superconformal index in a Cardy-like limit is achieved. </jats:p>
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Journal articleMatt C, G羹ltekin K, Agazie G, et al., 2026, , Astrophysical Journal, Vol: 1006, ISSN: 0004-637X
The observed gravitational-wave background (GWB) spectrum is higher in amplitude than model predictions by a factor of 2–3. Using a semi-analytic model, we evaluate the effect of a high-scatter supermassive black hole (SMBH) scaling relation (M<inf>BH</inf>–M<inf>bulge</inf>) on models of the nanohertz GWB. By implementing an intrinsic scatter of the M<inf>BH</inf>–M<inf>bulge</inf> relation, which is larger at higher redshift, but matches local observations, we find that the amplitude of GWB models increases to be consistent with the low-frequency end of the GWB spectrum. This amplitude increase is not uniform across frequencies, a strongly evolving scatter preferentially increases the number density of the most massive SMBHs which, in the GWB spectrum, minimizes the strength of the low-frequency turnover. Our models with positively evolving intrinsic scatter can reproduce the electromagnetically observed overmassive SMBHs at 4 < z < 6 without changing the M<inf>BH</inf>–M<inf>bulge</inf> normalization though we find that including moderate normalization evolution marginally improves fits to the GWB data. We conclude that the M<inf>BH</inf>–M<inf>bulge</inf> relation which best describes the available GWB and electromagnetic data sets has intrinsic scatter that evolves as (Formula presented) ε(z)=ε0+(0.56±0.4)log10(1+z) and normalization that evolves as α(z) = α<inf>0</inf>(1 + z)<sup>0.84±0.35</sup>. The results of this work imply that the M<inf>BH</inf>–M<inf>bulge</inf> relation we see today is not universal throughout cosmic time and that a diversity of seeding models and growth mechanisms may be at play in the early stages of SMBH–galaxy evolution.
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Journal articleBorissova J, Magueijo J, 2026, , Journal of Cosmology and Astroparticle Physics, Vol: 2026
Quasi-topological theories of gravity are known to resolve black-hole singularities. We investigate whether the same mechanism can remove cosmological singularities. Focusing on non-polynomial curvature quasi-topological gravities in d = 4 dimensions, we find three generic scenarios with the correct infrared limit but without a Big-Bang singularity, for universes filled with pure radiation or other standard matter. The first scenario yields a universe emerging from a de Sitter phase, a case for which the curvature invariants remain finite but the matter density diverges, albeit only at infinite affine distance. The second one corresponds to a bouncing universe, and requires a multi-valued Lagrangian. The third possibility is an asymptotically Minkowski origin, reminiscent of an eternally loitering universe. The matter energy density for this solution is non-singular even at infinite affine distance and does not enter a super-Planckian regime, but is instead approximately constant for the past eternity.
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Journal articleBennett S, Hanany A, Kalveks R, 2026, , Journal of High Energy Physics, Vol: 2026
This paper explores 3d N = 4 quiver gauge theories whose moduli spaces represent nilpotent orbits, Sodowy slices or, more generally, Sodowy intersections, which span the Special Pieces of nilcones of Classical or Exceptional algebras. We introduce a map between magnetic and electric quivers containing symmetric group actions, such as wreathings (or loops), bouquets, and/or non-simply laced foldings, which can be related to symmetric subgroups of Lusztig’s canonical quotient groups for Special Pieces. This map on quivers induces a new map on nilpotent orbits that partially resolves the obstruction to quiver dualities presented by the non-involutive nature of the Lusztig Spaltenstein and Barbasch Vogan maps. We use Coulomb and Higgs branch quiver methods complemented by localisation formulae for verification. Some new quivers for intersections within Exceptional nilcones are presented.
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Journal articleBennett S, Hanany A, Kumaran G, et al., 2026, , Journal of High Energy Physics, Vol: 2026
This letter considers 3d N = 4 (unitary-)orthosymplectic quiver gauge theories originating from Type IIA and Type IIB brane systems with ON<sup>0</sup> planes. Such theories lie outside the scope of present combinatorial techniques for Coulomb branch symmetry and symplectic stratification. It turns out that the correct prescription involves ‘symmetry mitosis’: a common subset of nodes in two linear balanced chains source two factors of a Coulomb branch global symmetry instead of one; the correct Coulomb branch Hasse diagram is obtained by a ‘doubling’ procedure on that computed by naive quiver subtraction. Input from 6d SQFTs and little string theories allows for the construction of various ‘mitotic’ magnetic quivers. The full Higgs branch Hasse diagram of minimal (E<inf>6</inf>, E<inf>6</inf>) conformal matter is given. Additionally, a new Type I<sup>′</sup> brane system using eight full D8 branes, negatively charged D6 branes, and ON<sup>0</sup> planes is found corresponding to a product of Spin(32) instantons on <sup>2</sup>. The corresponding 6d theory uses Sp(−1) gauge nodes which have the interpretation of bi-spinor matter of O(a) and O(12 − a) for a = 0, 1, · · ·, 12.
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Journal articleBennett S, Hanany A, Kumaran G, 2026, , Journal of High Energy Physics, Vol: 2026
Quotient quiver subtraction is a simple combinatorial prescription for gauging Coulomb branch isometry subgroups of 3d N = 4 quiver gauge theories. This paper uses Type IIB brane constructions with O5 planes to extend the prescription to gauge Sp(n), SO(n), and Sp(n) coupled to a half-hypermultiplet Coulomb branch isometry subgroups of quivers with unitary gauge groups. The gauging procedure is no longer solely a subtraction — additional steps change the graph type. The method is applied to provide alternative constructions of the Higgs branch of certain SCFTs in higher dimensions.
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Journal articleAgazie G, Anumarlapudi A, Archibald AM, et al., 2026, , Astrophysical Journal Letters, Vol: 1004, ISSN: 2041-8205
The NANOGrav 15 yr (NG15) data set provides evidence for a gravitational-wave background (GWB) signal at nHz frequencies, which is expected to originate either from a cosmic population of inspiraling supermassive black hole binaries or new particle physics in the early Universe. A firm identification of the source of the NG15 signal requires an accurate reconstruction of its frequency spectrum. In this Letter, we provide such a spectral characterization of the NG15 signal based on a piecewise power-law (PPL) ansatz that strikes a balance between existing alternatives in the literature. Our PPL reconstruction is more flexible than the standard constant power-law model, which describes the GWB spectrum in terms of only two parameters: an amplitude A and a spectral index γ. Concurrently, it better approximates physically realistic GWB spectra—especially those of cosmological origin—than the free spectral model, since the latter allows for arbitrary variations in the GWB amplitude from one frequency bin to the next. Our PPL reconstruction of the NG15 signal relies on individual PPL models with a fixed number of internal nodes (i.e., constant power law, broken power law, doubly broken power law, etc.), which are ultimately combined in a Bayesian model average. The data products resulting from our analysis provide the basis for fast refits of spectral GWB models.
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Journal articleVaglio M, Falxa M, Mentasti G, et al., 2026, , Physical Review D, Vol: 113, ISSN: 2470-0010
Astrometric missions like Gaia provide exceptionally precise measurements of stellar positions, parallaxes, and proper motions. Gravitational waves traveling between the observer and distant stars can induce small, correlated shifts in their apparent positions, a phenomenon known as astrometric deflection. The precision and scale of astrometric datasets make them well suited for searching for a stochastic gravitational-wave background, whose signature appears in the two-point correlation function of the deflection field across the sky. In space-based astrometry, the ultimate sensitivity of such measurements is reduced by systematic uncertainties in the satellite’s absolute attitude reconstruction, which constrain the accuracy of absolute astrometry. These orientation errors can be mitigated by focusing on relative angular separation between pairs of stars, which effectively cancel out common-mode orientation noise. In this work, we compute the astrometric response and the overlap reduction functions for this differential approach, correcting previous expressions presented in the literature. We use a Fisher matrix analysis to compare the sensitivity of differential astrometry to that of conventional absolute astrometry. Our analysis shows that while the differential method is theoretically sound, its sensitivity is limited for closely spaced star pairs. Pairs with large angular separations provide competitive sensitivity, but, when considered in connection with Gaia, it is unclear whether the differential strategy would be effective, since instrumental systematics are not expected to remain correlated on such scales. Finally, we demonstrate that combining astrometric data with observations from pulsar-timing arrays leads to slight improvements in sensitivity at frequencies 10−7 Hz.
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Journal articleVicente Garc穩a-Consuegra L, Rajantie A, 2026, , Physical Review D, Vol: 113, ISSN: 2470-0010
<jats:p>We investigate two different definitions of a scalar field effective potential in quantum field theory in de Sitter spacetime: the standard textbook definition, and the constraint effective potential proposed by O’Raifeartaigh in 1986. While these definitions are equivalent in Minkowski spacetime, they differ significantly in de Sitter spacetime. We demonstrate this by computing them both explicitly at one-loop order in perturbation theory. It is well known that the perturbative expansion of the standard effective potential fails to converge for light fields. In contrast, the constraint effective potential does not suffer from this infrared problem, and it can therefore be computed using perturbation theory. We discuss the physical interpretation of the two effective potentials. In particular, we provide evidence supporting an earlier conjecture that the constraint effective potential is the correct one to use in the stochastic Starobinsky-Yokoyama theory.</jats:p>
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Journal articleIsichei R, Magueijo J, 2026, , Phys Rev Lett, Vol: 136
We show that general relativity and other geometrical theories can be viewed as a degenerate Otto cycle with only heat-exchange legs in emergent gravity. Including work-producing legs yields controlled violations of local Lorentz invariance and energy-momentum conservation, which produce late-time cosmological acceleration. Implications for the cosmological constant problem, structure formation, and local observations are discussed.
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Journal articleTseytlin AA, Wang Z, 2026, , Physical Review D, Vol: 113, ISSN: 2470-0010
<jats:p> Type-IIB string theory on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mtext>AdS</a:mtext> <a:mn>3</a:mn> </a:msub> <a:mo>×</a:mo> <a:msup> <a:mi>S</a:mi> <a:mn>3</a:mn> </a:msup> <a:mo>×</a:mo> <a:msup> <a:mi>T</a:mi> <a:mn>4</a:mn> </a:msup> </a:math> with Ramond–Ramond flux as the near-horizon limit of the D1-D5 solution is expected to be dual to a (4, 4) supersymmetric 2D conformal field theory (CFT) parametrized by the integers <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msub> <c:mi>Q</c:mi> <c:mn>1</c:mn> </c:msub> </c:math> , <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>Q</e:mi> <e:mn>5</e:mn> </e:msub> </e:math> , and other moduli. It is related by T-duality to type-IIA string theory in the near-horizon limit of the D2-D4 solution, which admits an uplift to the 11D <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inl
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Journal articleArav I, Gauntlett JP, Roberts MM, et al., 2026, , Journal of High Energy Physics (JHEP), Vol: 2026, ISSN: 1126-6708
We construct AdS3 × Y7 solutions of type IIB supergravity, where Y7 is a smooth S5 bundle over a spindle Σ(nN, nS), which are dual to = (0, 2) SCFTs in d = 2. The solutions are constructed using the D = 5 STU U(1)3 gauged supergravity theory coupled to a hyperscalar charged under U(1)B. We investigate spindle solutions with two new features: first, we allow (nN, nS) to be non-coprime integers, including orbifolds of the round S2, which can lead to non-unique, inequivalent uplifts, distinguished by the hyperscalar spectra, for given magnetic flux through the spindle. Second, we also allow the hyperscalar to vanish at the poles leading to solutions carrying non-vanishing U(1)B flux. The new hyperscalar AdS3 solutions can naturally arise as the endpoint of RG flows, triggered by relevant hyperscalar deformations of the AdS3 solutions of the STU model.
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Journal articleHull C, 2026, , Journal of High Energy Physics, Vol: 2026
The action for self-dual gauge fields that emerges from the recently constructed superstring field theory is found. The new superstring field theory reduces to that of Sen in a certain limit, and in this limit the new action for self-dual gauge fields reduces to Sen’s action for such fields. The theory describes two decoupled self-dual gauge fields that couple to two metrics, with each gauge field coupling to only one of the metrics. The action also features a background metric, and the non-linear coupling to these three metrics is non-standard. There are two spin-two gauge invariances, and diffeomorphisms arise from the diagonal subgroup.
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Journal articleChiang HW, de Rham C, Garcia-Saenz S, et al., 2026, , Journal of Cosmology and Astroparticle Physics, Vol: 2026
We study the cosmological predictions of (extended) Proca-Nuevo theory. This vector-tensor theory enjoys stable homogeneous and isotropic solutions characterized by an effective dark energy fluid, with behavior that ranges from freezing quintessential to thawing phantom-like, serving as a motivated framework to scrutinize the cosmological tensions that affect the standard ΛCDM model. While the model we consider is sufficiently generic to encompass a large class of field theories, it distinguishes itself from scalar dark energy models (quintessential ones, kinetic ones and non-minimally coupled ones) by the presence of what would be classed as a vector degree of freedom which can be for instance inherited from more generic theories of gravity. We improve on previous work in several directions: we consider a general one-parameter class of background models; identify a so-called 'special' model and analyze observational constraints taking also into account perturbations and making use of wide up-to-date catalogs of datasets including recently released ones. We find that the one-parameter Proca-Nuevo model is preferred over ΛCDM at 1.5σ when fitting CMB and BAO data, and at 2.4σ when further adding low-redshift data. The Hubble tension is alleviated, dropping from 5.σ to 2.3σ (resp. 1.5σ) between CMB with (and resp. without) BAO data and local measurements. On the other hand, we find that the vector field generically introduces a significant enhancement of the effective Newton constant for natural values of parameters, so that matching the observed matter power spectrum requires a mild amount of tuning to suppress the impact of perturbations. Since, at the background level, Proca-Nuevo is degenerate with other classes of theories, our results are also relevant to a wider range of set-ups including and beyond vector-tensor models.
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Journal articlede Rham C, Jaitly S, Kaplanek G, 2026, , Journal of High Energy Physics, Vol: 2026
In theories with multiple particle species standard fixed-t positivity bounds do not directly apply to 2-to-2 definite species scattering amplitudes when the initial and final state are not the same (inelastic processes). These inelastic amplitudes are nevertheless constrained by positivity bounds indirectly, by considering scattering states which are arbitrary superpositions of definite species two-particle states. While these ‘superposition bounds’ have been studied and utilised extensively in the past, earlier analyses typically consider cases insensitive to relative particle masses and IR branch cuts. Here we derive new families of bounds that take account and depend explicitly on mass differences between species making no assumption of weak-coupling. We emphasise unusual non-analyticities induced by the IR mass difference within the superposition amplitude and use fixed (backwards) angle dispersion relations to prove our bounds. We then discuss extensions of our results to ‘improved bounds’, with implications worth exploring for pions and other EFTs of the Standard Model and Beyond, particularly where IR branch cuts are non-negligible.
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Journal articleChester SM, Mouland R, van Muiden J, et al., 2026, , Journal of High Energy Physics, Vol: 2026
We consider M-theory on the backgrounds AdS4×S7/刁f and AdS<inf>7</inf> × S<sup>4</sup>/<inf>2</inf>, which have fixed point loci AdS<inf>d+1</inf> × S<sup>3</sup> for d = 3, 6. These theories are holographically dual to certain CFTs in d = 3, 6 with eight supercharges. We compute the bulk cubic couplings between graviton KK modes and gluon KK modes living on the fixed points of these theories, which are generically extremal. We use these couplings to compute the graviton exchange term that appears in the strong coupling expansion of holographic correlators of gluon KK modes 22pp in these theories, and check that it matches the expected flat space limit. We express the answer in terms of a new reduced correlator solution to the superconformal Ward identities, which we derive for all CFTs with eight supercharges in 3 ≤ d ≤ 6.
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Journal articleGersbach KA, Taylor SR, B矇csy B, et al., 2026, , Physical Review D, Vol: 113, ISSN: 2470-0010
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Journal articleChester SM, Piazza A, Reehorst M, et al., 2026, , Physical Review D, Vol: 113, ISSN: 2470-0010
<jats:p> We study the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>N</a:mi> <a:mo>=</a:mo> <a:mn>3</a:mn> </a:math> case of the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>C</c:mi> <c:msup> <c:mi>P</c:mi> <c:mrow> <c:mi>N</c:mi> <c:mo>−</c:mo> <c:mn>1</c:mn> </c:mrow> </c:msup> </c:math> model, which is a field theory of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>N</e:mi> </e:math> complex scalars in <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mn>3</g:mn> <g:mi>d</g:mi> </g:math> coupled to an Abelian gauge field with <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>S</i:mi> <i:mi>U</i:mi> <i:mo stretchy="false">(</i:mo> <i:mi>N</i:mi> <i:mo stretchy="false">)</i:mo> <i:mo>×</i:mo>
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Journal articleElder B, Gawrych K, Rajantie A, 2026, , Journal of High Energy Physics (JHEP), Vol: 2026, ISSN: 1126-6708
Instantons, localised saddle points of the action, play an important role in describing non-perturbative aspects of quantum field theories, for example vacuum decay or violation of conservation laws associated with anomalous symmetries. However, there are theories in which no saddle point exists. In this paper, we revisit the idea of constrained instantons, proposed initially by Affleck in 1981, and develop it into a complete method for computing the vacuum decay rate in such cases. We apply this approach to the massive scalar field theory with a negative quartic self-interaction using two different constraints. We solve the field equations numerically and find a two-branch structure, with two distinct solutions for each value of the constraint. By counting the negative modes, we identify one branch of solutions as the constrained instantons and the other as the minima of the action subject to the constraint. We discuss their significance for the computation of the vacuum decay rate.
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Journal articleChen Y, Daniel M, DOrazio DJ, et al., 2026, , Nature Astronomy, Vol: 10, Pages: 554-563
The detection of a stochastic gravitational wave background by pulsar-timing arrays indicates the presence of a population of supermassive black hole binaries. Although the observed spectrum generally matches predictions for orbital evolution driven by gravitational-wave emission in circular orbits, there is a preference for a spectral turnover at the lowest observed frequencies, which may point to substantial hardening during a transition from early environmental influences to later stages dominated by emission. In the vicinity of these binaries, the ejection of stars or dark matter particles through gravitational three-body slingshots efficiently extracts orbital energy, leading to a low-frequency turnover in the spectrum. Here we model how the gravitational-wave spectrum depends on the initial inner galactic profile before scouring by binary ejections while accounting for a range of initial binary eccentricities. By analysing the NANOGrav 15-year data, we find that a parsec-scale galactic-centre density of around 10<sup>6</sup> M<inf></inf> pc<sup>−</sup><sup>3</sup> is favoured across most of the parameter space, thus shedding light on the environmental effects that shape black hole evolution and the combined matter density near galaxy centres.
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Journal articleBeccaria M, Kurlyand SA, Tseytlin AA, 2026, , Nuclear Physics B, Vol: 1025, ISSN: 0550-3213
The exact localization result for the expectation value of the 12 BPS circular Wilson loop in N=4 SYM theory is given in the planar limit by the famous Bessel function expression: W=2NλI<inf>1</inf>(λ). Expanded in large λ and expressed in terms of the AdS<inf>5</inf> × S <sup>5</sup> string tension T=λ2π this gives W=T2πg<inf>s</inf>e<sup>2πT</sup>(1−316πT<sup>−1</sup>+…).The exponential is matched by the value of the action of the string with the AdS<inf>2</inf> world volume while the prefactor comes from the 1-loop GS string correction. Here we address the question of how the subleading T<sup>−1</sup> term could be reproduced by the 2-loop correction in the corresponding partition function of the AdS<inf>5</inf> × S <sup>5</sup> GS string expanded near the AdS<inf>2</inf> minimal surface. We find that the string correction contains a non-zero UV logarithmic divergence implying that comparison with the SYM result requires a particular subtraction prescription. We discuss implications of this conclusion for checking the AdS/CFT duality at strong coupling.
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