We explore the possibility of detecting gravitational waves generated by first-order phase transitions in multiple dark sectors. $N$ naturalness is taken as a sample model that features multiple additional sectors, many of which undergo phase transitions that produce gravitational waves. We examine the cosmological history of this framework and determine the gravitational wave profiles generated. These profiles are checked against projections of next-generation gravitational wave experiments, demonstrating that multiple hidden sectors can indeed produce unique gravitational wave signatures that will be probed by these future experiments.

The sensitivity of future electron-proton colliders, the LHeC and FCC-eh, to weakly produced supersymmetric particles is evaluated in this paper. Supersymmetric scenarios where charginos (${\tilde{\chi }}_1^{\pm }$) and neutralinos (${\tilde{\chi }}_1^0$ and ${\tilde{\chi }}_2^0$) are nearly degenerate in mass are considered. Two sets of models, which differ in the mass of sleptons ($\tilde{\ell }$), are studied. Under the hypothesis that slepton masses are at the multi-TeV scale (“decoupled” scenario), the production processes for charginos and neutralinos at $ep$ colliders, $p{e}^{-}\to j{e}^{-}\tilde{\chi }\tilde{\chi }$ with $\tilde{\chi }={\tilde{\chi }}_1^0$, ${\tilde{\chi }}_1^{\pm }$ or ${\tilde{\chi }}_2^0$, are considered. For the models where slepton masses are above but close to ${\tilde{\chi }}_1^{\pm }$, ${\tilde{\chi }}_2^0$ masses (“compressed” scenario), contributions from the processes $p{e}^{-}\to j\tilde{\chi }{\tilde{e}}_L^{-}$ and $j\tilde{\chi }\tilde{\nu }$ followed by the decays ${\tilde{e}}_L^{-}\to {\tilde{\chi }}_{1,2}^0+e^{-}$ and $\tilde{\nu }\to {\tilde{\chi }}_1^{+}+e^{-}$ are also taken into account. These scenarios are analyzed with realistic detector performance, using multivariate techniques. Effects of systematic uncertainties and electron beam polarization dependence are also discussed. The reach is found to be complementary to the one obtained at $pp$ colliders, in particular for the compressed-slepton scenario.

We build a minimal neutral naturalness model in which the top partners are not charged under QCD, with a pseudo Nambu-Goldstone Higgs arising from $SO(5)/SO(4)$ breaking. The color-neutral top partners generate the Higgs potential radiatively without quadratic divergence. The misalignment between the electroweak scale and global symmetry breaking scale is naturally obtained from suppression of the Higgs quadratic term, due to cancellation between singlet and doublet top partner contributions. This model can be embedded into ultraviolet holographic setup in composite Higgs framework, which even realizes finite Higgs potential.

Differences in lepton number (i.e., $L_e-L_{\mu }$, $L_e-L_{\tau }$, $L_{\mu }-L_{\tau }$, or combinations thereof) are not conserved charges in the Standard Model due to the observation of neutrino oscillations. We compute the divergence of the corresponding currents in the case of Majorana or Dirac-type neutrinos and show that, in the high energy limit, the vector interactions map onto those of a light scalar coupled to neutrinos with its coupling fixed by the observed neutrino masses and mixing. This leads to amplitudes with external light vectors that scale inversely with the vector mass. By studying these processes, we set new constraints on $L_i-L_j$ through a combination of semileptonic meson decays, invisible neutrino decays, neutrinoless double beta decays, and observations of big bang nucleosynthesis/supernova, which can be much stronger than previous limits for vector masses below an eV. These bounds have important implications on the experimental prospects of detecting $L_i-L_j$ long-range forces.

We study baryon-number-violating processes, including proton and bound neutron decays and $n-\overline{n}$ oscillations, in a left-right-symmetric (LRS) model in which quarks and leptons have localized wave functions in extra dimensions. In this model we show that, while one can easily suppress baryon-number-violating nucleon decays well below experimental bounds, this does not suppress $n-\overline{n}$ transitions, which may occur at levels comparable to current limits. This is qualitatively similar to what was found in an extra-dimensional model with a Standard-Model low-energy effective field theory (SMEFT). We show that experimental data imply a lower limit on the mass scale $M_{n\overline{n}}$ characterizing the physics responsible for $n-\overline{n}$ oscillations in the LRS model that is significantly higher than in the extra-dimensional model using a SMEFT and explain the reason for this. Our results provide further motivation for new experiments to search for $n-\overline{n}$ oscillations.

We explore the possibility of observing odderon exchange in the $pp\to pp{K}^{+}{K}^{-}$ and $pp\to pp{\mu }^{+}{\mu }^{-}$ reactions at the LHC. We consider the central exclusive production (CEP) of the $\varphi (1020)$ resonance decaying into $K^{+}{K}^{-}$ and ${\mu }^{+}{\mu }^{-}$. We compare the purely diffractive contribution (odderon-Pomeron fusion) to the photoproduction contribution (photon-Pomeron fusion). The theoretical results are calculated within the tensor-Pomeron and vector-odderon model for soft reactions. We include absorptive corrections at the amplitude level. In order to fix the coupling constants for the photon-Pomeron fusion contribution we discuss the reactions $\gamma p\to \omega p$ and $\gamma p\to \varphi p$ including $\varphi \text{−}\omega$ mixing. We compare our results for these reactions with the available data, especially those from HERA. Our coupling constants for the Pomeron-odderon-$\varphi$ vertex are taken from an analysis of the WA102 data for the $pp\to pp\varphi$ reaction. We show that the odderon-exchange contribution significantly improves the description of the $pp$ azimuthal correlations and the ${\mathrm{dP}}_{\mathrm{t}}$ “glueball-filter variable” dependence of $\varphi$ CEP measured by WA102. To describe the low-energy data more accurately we consider also subleading processes with Reggeized vector-meson exchanges. However, they do not play a significant role at the LHC. We present predictions for two possible types of measurements: at midrapidity and with forward measurement of protons (relevant for ATLAS-ALFA or CMS-TOTEM), and at forward rapidities and without measurement of protons (relevant for LHCb). We discuss the influence of experimental cuts on the integrated cross sections and on various differential distributions. With the corresponding LHC data one should be able to get a decisive answer concerning the presence of an odderon-Pomeron fusion contribution in single $\varphi$ CEP.

We compare the cross section for exclusive $J/\psi$ photoproduction calculated at next-to-leading order (NLO) in the collinear factorization approach with HERA and LHCb data. Using the optimum scale formalism together with the subtraction of the low $k_t$ contribution (below the input scale $Q_0$) from the NLO coefficient function to avoid double counting, we show that the existing global parton distribution functions (PDFs) are consistent with the data within their uncertainties. This is the first time that $J/\psi$ production data at HERA were successfully described within the NLO collinear factorization framework using the PDFs of the global parton analyses. However, at lower $x$ the uncertainties of the present global PDFs are large. On the other hand, the accuracy of the LHCb data are rather good. Therefore, these data provide the possibility to directly measure the gluon PDF over the very large interval of $x$, ${10}^{-6}<x<{10}^{-2}$, at a fixed low scale.

We study fermionic excitations in a hot and dense strongly interacting medium consisting of quarks and (pseudo-)scalar mesons. In particular, we use the two-flavor quark-meson model in combination with the functional renormalization group (FRG) approach, which allows to take into account the effects from thermal and quantum fluctuations. The resulting fermionic excitation spectrum is investigated by calculating the quark spectral function at finite temperature, quark chemical potential, and spatial momentum. This involves an analytic continuation from imaginary to real energies by extending the previously introduced analytically continued FRG method to the present case. We identify three different collective excitations in the medium: the ordinary thermal quark, the plasmino mode, and an ultrasoft “phonino” mode. The dispersion relations of these modes are extracted from the quark spectral function. When compared to corresponding results from an FRG-improved one-loop calculation, a remarkable agreement has been found.

This study is performed with the aim of gaining insights into the possible applicability of the quark-hadron continuity concept, not only in the idealized case of three-flavor symmetric quark matter, but also for the transition from neutron matter to two-flavor quark matter. A key issue is the continuity between neutron superfluidity and a corresponding superfluid quark phase produced by $d$-quark pairing. Symmetry arguments are developed and relevant dynamical mechanisms are analyzed. It is pointed out that the ${}^3{P}_2$ superfluidity in dense neutron matter has a direct analog in the ${}^3{P}_2$ pairing of $d$-quarks in two-flavor quark matter. This observation supports the idea that the quark-hadron continuity hypothesis may be valid for such systems. Possible implications for neutron stars are briefly discussed.

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a $558{\mathrm{fb}}^{-1}$ data sample collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

We analyze gravitationally localized states of multiple fermions with high angular momenta, in the formalism introduced by Finster, Smoller, and Yau [Phys Rev. D 59, 104020 (1999)]. We show that the resulting solitonlike wave functions can be naturally interpreted in terms of a form of self-trapping, where the fermions become localized on shells the locations of which correspond to those of “bulges” in the optical geometry created by their own energy density.

We obtain the solution of a static spherically symmetric black hole surrounded by a cloud of strings in Rastall gravity and study the influence of the parameter $a$ associated with strings on the event horizon and the Hawking temperature. Through analyzing the black hole metric, we find that the static spherically symmetric black hole solution surrounded by a cloud of strings in Rastall gravity can be transformed into the static spherically symmetric black hole solution surrounded by quintessence in Einstein gravity when the parameter $\beta$ of Rastall gravity is positive, which provides a possibility for the string fluid to be a candidate of dark energy. We use the method of Regge and Wheeler together with the high order WKB-Padé approximation to calculate the quasinormal mode frequencies of the odd parity gravitational perturbation and simultaneously apply the unstable null geodesics of black holes to compute the quasinormal mode frequencies at the eikonal limit for this black hole model. The results show that the increase of the parameter $a$ makes the gravitational wave decay slowly in Rastall gravity. In addition, we utilize two methods, which are based on the adiabatic invariant integral and the periodic property of outgoing waves, respectively, to derive the area spectrum and entropy spectrum of the black hole model. The results show that the area spectrum and entropy spectrum are equidistant spaced. The former is the same as the case of Einstein gravity, while the latter is different, depending on the Rastall parameter $\beta$.

Thin shell wormholes are constructed by joining two asymptotically flat spacetimes along their inner boundaries. The junction conditions imposed on the spacetimes specify the equation of state of the matter called thin shell distributed along the joined boundaries. Barcelo and Visser (2000) reported that spherically symmetric thin shell wormholes have their shells, namely the wormhole throats, on the photon spheres if the wormholes are $Z_2$-symmetric across the throats and the shells are of pure tension. In this paper, first, we consider general joined spacetimes (JSTs) and show that any $Z_2$-symmetric pure-tensional JST (Z2PTJST) of $\mathrm{\Lambda }$-vacuum has its shell on a photon surface, a generalized object of photon spheres, without assuming any other symmetries. The class of Z2PTJSTs also includes, for example, brane world models with the shells being the branes we live in. Second, we investigate the shell stability of Z2PTJSTs by analyzing the stability of the corresponding photon surfaces. Finally, applying the uniqueness theorem of photon spheres by Cederbaum [Contemp. Math. 653, 86 (2015)], we establish the uniqueness theorem of static wormholes of Z2PTJST.

Late times dark energy transitions at redshifts $z\ll 0.1$ can raise the predicted value of the Hubble constant to the SH0ES value, $74.03\pm 1.42(\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1})$ or more, while providing an equally good fit as $\mathrm{\Lambda }\mathrm{CDM}$ at $67.73\pm 0.41$ to higher redshift data, in particular from the cosmic microwave background and baryon acoustic oscillations. These models however do not fully resolve the true source of tension between the distance ladder and high redshift observations: the local calibration of supernovae luminosities well out into the Hubble flow. When tested in this manner by transferring the SH0ES calibration to the Pantheon supernovae dataset, the ability of such transitions to raise the Hubble constant is reduced to $69.17\pm 1.09$. Such an analysis should also be used when testing any dynamical dark energy model which can produce similarly fine features in redshift or local void models.

It has been recently suggested [F. Bezrukov et al. J. Cosmol. Astropart. Phys. 06 (2017) 051; F. Bezrukov et al. Phys. Rev. D 99, 083507 (2019)] that a cosmic scalar field can completely change the keV-scale sterile neutrino production in the early Universe. Its effect may, for various parameter choices, either suppress sterile neutrino production and make moderate active-sterile mixing cosmologically acceptable, or increase the production and generate a considerable dark matter component out of sterile neutrino with otherwise negligible mixing with SM. In this paper, we provide analytic estimates complementing and improving of the numerical calculations performed by F. Bezrukov et al. [Phys. Rev. D 99, 083507 (2019) in the case of the resonant amplification of the sterile neutrino production by the scalar field. We found the substantially cooler velocity distribution of sterile neutrinos as compared to most production mechanisms, opening a new window for warm dark matter, which is otherwise forbidden by structure formation considerations. We also discuss phenomenological and theoretical issues related to the successful implementation of this idea in fully realistic extensions of the Standard Model of particle physics.

The possibility that in the mass range around ${10}^{-12}{M}_{\odot }$ most of dark matter is constituted of primordial black holes (PBHs) is a very interesting topic. To produce PBHs with this mass, the primordial scalar power spectrum needs to be enhanced to the order of 0.01 at the scale $k\sim {10}^{12}{\mathrm{Mpc}}^{-1}$. The enhanced power spectrum also produces large secondary gravitational waves at the mHz band. A phenomenological delta function power spectrum is usually used to discuss the production of PBHs and secondary gravitational waves. Based on $k$ and $G$ inflations, we propose a new mechanism to enhance the power spectrum at small scales by introducing a noncanonical kinetic term $[1-2G(\varphi )]X$ with the function $-G(\varphi )$ having a peak. Away from the peak, $G(\varphi )$ is negligible and we recover the usual slow-roll inflation which is constrained by the cosmic microwave background anisotropy observations. Around the peak, the slow-roll inflation transiently turns to ultra slow-roll inflation. The enhancement of the power spectrum can be obtained with generic potentials, and there is no need to fine tune the parameters in $G(\varphi )$ to several significant digits. The energy spectrum ${\mathrm{\Omega }}_{\mathrm{GW}}(f)$ of secondary gravitational waves produced by the model have the characteristic power law behavior ${\mathrm{\Omega }}_{\mathrm{GW}}(f)\sim f^n$ and is testable by pulsar timing array and space based gravitational wave detectors.

In the context of string theory, several conjectural conditions have been proposed for low energy effective field theories not to be in swampland, the UV-incomplete class. The recent ones represented by the de Sitter and trans-Planckian censorship conjectures in particular seem to conflict with the inflation paradigm of the early universe. We first point out that scenarios where inflation is repeated several times (multiphase inflation) can be easily compatible with these conjectures. In other words, we relax the constraint on the single inflation for the large scale perturbations to only continue at least around 10 e-folds. In this context, we then investigate if a spectator field can be a source of the almost scale-invariant primordial perturbations on the large scale. As a consequence of such an isocurvature contribution, the resultant perturbations exhibit the nonvanishing non-Gaussianity in general. Also the perturbation amplitude on smaller scales can be completely different from that on the large scale due to the multiplicity of inflationary phases. These signatures will be a smoking gun of this scenario by the future observations.

Dark matter axion condensates may experience stimulated decays into photon pairs. This effect has been often interpreted as a parametric resonance of photons from the axion-photon coupling, leading to an exponential growth of the photon occupation number in a narrow instability band. Most of the previous literature does not consider the possible evolution of the axion field due to the photon growth. We revisit this effect presenting a mean field solution of the axion-photon kinetic equations, in terms of number of photons and pair correlations. We study the limit of no axion depletion, recovering the known instability. Moreover, we extend the results including a possible depletion of the axion field. In this case we find that the axion condensate exhibits the behavior of an inverted pendulum. We discuss the relevance of these effects for two different cases: a homogeneous axion field at recombination and a localized axion clump and discuss constraints that could result from the induced photon background.

The reported association of high-energy neutrino event IceCube-170922A and blazar TXS $0506+056$ has sparked discussion about blazars as sources of cosmic neutrinos. In this paper, we use publicly released IceCube data and blazar locations from Roma-BzCat to test spatial correlation between neutrino events and blazar locations. We also scrutinize the correlation between the $\gamma$-ray flux and neutrino flux of blazars by applying a temporal filter onto the data based on the Fermi monitored source list. We find no compelling evidence to prove blazars as the main source of cosmic neutrinos, as known before the detected IceCube-170922A/TXS $0506+056$ association. While we do not rule out the association between IceCube-170922A and TXS $0506+056$, the significance level we obtained is not high enough to claim a strong association. If such an association is real, a special physical condition is desired to allow a small fraction of blazars to become bright neutrino sources.