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A bstract Recent works have suggested that nonlinear (quadratic) effects in black hole perturbation theory may be important for describing a black hole ringdown. We show that the technique of uniform approximations can be used to accurately compute 1) nonlinear amplitudes at large distances in terms of the linear ones, 2) linear (and nonlinear) quasi-normal mode frequencies, 3) the wavefunction for both linear and nonlinear modes. Our method can be seen as a generalization of the WKB approximation, with the advantages of not losing accuracy at large overtone number and not requiring matching conditions. To illustrate the effectiveness of this method we consider a simplified source for the second-order Zerilli equation, which we use to numerically compute the amplitude of nonlinear modes for a range of values of the angular momentum number.

A bstract We derive causality constraints on the simplest scalar-tensor theories in which black holes differ from what General Relativity predicts, a scalar coupled to the Gauss-Bonnet or the Chern-Simons terms. Demanding that time advances are unobservable within the regime of validity of these effective field theories, we find their cutoff must be parametrically of the same size as the inverse Schwarzschild radius of the black holes for which the non-standard effects are of order one. For astrophysical black holes within the range of current gravitational wave detectors, this means a cutoff length of the order of kilometers. We further explore the leading additional higher-dimensional operators potentially associated with the scale of UV completion and discuss their phenomenological implications for gravitational wave science.

A bstract It has been shown that some Lorentz-invariant quantum field theories, such as those with higher-dimensional operators with negative coefficients, lead to superluminality on some classical backgrounds. While superluminality by itself is not logically inconsistent, these theories also predict the formation of closed time-like curves at the classical level, starting from initial conditions without such curves. This leads to the formation of a Cauchy Horizon which prevents a complete description of the time evolution of such systems. Inspired by the chronology protection arguments of General Relativity, we show that quantum mechanical effects from low energy quanta strongly backreact on such configurations, exciting unknown short-distance degrees of freedom and invalidating the classical predictions. Thus, there is no obvious low-energy obstruction to the existence of these operators.

A bstract We investigate how the speed of propagation of physical excitations is encoded in the coefficients of five-point interactions. This leads to a superluminality bound on scalar five-point interactions, which we present here for the first time. To substantiate our result, we also consider the case of four-point interactions for which bounds from S-matrix sum rules exist and show that these are parametrically equivalent to the bounds obtained within our analysis. Finally, we extend the discussion to a class of higher-point interactions.

A bstract We study bounds arising from the analyticity and unitarity of scattering amplitudes in the context of effective field theories with massless particles. We provide an approach that only uses dispersion relations away from the forward limit. This is suitable to derive constraints in the presence of gravity, in a way that is robust with respect to radiative corrections. Our method not only allows us to avoid the Coulomb pole, but also the singularities associated with calculable loop effects, which would otherwise diverge.

We prove that, in the first Heisenberg group  H , an entire locally Lipschitz intrinsic graph admitting vanishing first variation of its sub-Riemannian area and non-negative second variation must be an intrinsic plane, i.e., a coset of a two dimensional subgroup of  H . Moreover two examples are given for stressing result’s sharpness.

A bstract Scalar hair of black holes in theories with a shift symmetry are constrained by the no-hair theorem of Hui and Nicolis, assuming spherical symmetry, time-independence of the scalar field and asymptotic flatness. The most studied counterexample is a linear coupling of the scalar with the Gauss-Bonnet invariant. However, in this case the norm of the shift-symmetry current J 2 diverges at the horizon casting doubts on whether the solution is physically sound. We show that this is not an issue since J 2 is not a scalar quantity, since J μ is not a diffinvariant current in the presence of Gauss-Bonnet. The same theory can be written in Horndeski form with a non-analytic function G 5 ∼ log X . In this case the shift-symmetry current is diff-invariant, but contains powers of X in the denominator, so that its divergence at the horizon is again immaterial. We confirm that other hairy solutions in the presence of non-analytic Horndeski functions are pathological, featuring divergences of physical quantities as soon as one departs from time-independence and spherical symmetry. We generalise the no-hair theorem to Beyond Horndeski and DHOST theories, showing that the coupling with Gauss-Bonnet is necessary to have hair.

We discuss Meyers-Serrin’s type results for smooth approximations of functions b = b ( t , x ) : R × R n → R m , with convergence of an energy of the form ∫ R ∫ R n w ( t , x ) φ | D b ( t , x ) | d x d t , where w > 0 is a suitable weight function, and φ : [ 0 , ∞ ) → [ 0 , ∞ ) is a convex function with φ ( 0 ) = 0 having exponential or subexponential growth.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that interacts with substrates, including microbial metabolites. Recent advances reveal that AhR is involved in the host response to coronaviruses (CoVs) infection. Particularly, AhR antagonists decrease the expression of angiotensin-converting enzyme 2 (ACE2) via AhR up-regulation, resulting in suppression of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in mammalian cells. Herein, we report that AhR is expressed in canine fibrosarcoma (A72) cells, where it is considerably activated by infection with genotype II of canine coronavirus (CCoV-II). The pharmacological inhibition of AhR, by CH223191, suppressed cell death signs and increased cell viability. Furthermore, the AhR antagonist induced a meaningful decline in virus yield, accompanied by the inhibition of the expression of viral nuclear protein (NP). Fascinatingly, during CCoV infection, a novel co-expression of NP and AhR expression was found. Taken together, our preliminary findings show that infection with CCoV activates AhR, and pharmacologic AhR inhibition reduces CCoV replication, identifying AhR as a possible candidate target for CCoV antiviral therapy.

Recurrent respiratory papillomatosis (RRP) is a condition caused by human papilloma virus (HPV) infection. Curative treatments aren't identifiable, and conservative surgery is often the best option to preserve respiratory functions. To date monoclonal antibodies are considered to be a treatment choice with both good efficacy and safety profile. A web-based search of MEDLINE/PubMed library from 2000 to 2024 of English-language papers was performed to identify articles by using \"respiratory or laryngeal papillomatosis\" and \"HPV respiratory infection, papillomatosis treatment, papillomatosis vaccine immunization, papillomatosis systemic treatment\". Furthermore, a manual screening of references from original articles was done to identify additional studies. We selected 34 articles. Since 2009, the systemic administration of Bevacizumab has been used to treat RRP not responding to surgical treatment. The efficacy of an anti-VEGF monoclonal antibody in RRP lesions can be related to their vascular nature. The major concern is the rebound papilloma growth within the cessation of treatment. An interesting solution could be the concomitant use of immunotherapy to both reduce the burden of residual disease and activate the immune system against the HPV-infected cells. Bevacizumab has a safe profile with a short-term local eradication of HPV. Further prospective research with long-term follow-up is needed to better define its safety and results against the disease recurrence. Considering the role of the anti-HPV vaccine, both, in the prophylaxis of the infection and in the adjuvant setting, the actual data underline the need for evaluation of its therapeutic efficacy for the management of RRP.