In this work, we investigate observational signatures of a primordial power spectrum with exponential infrared suppression, motivated by the choice of a nonoscillatory vacuum in a bouncing and inflationary geometry within loop quantum cosmology. We leave the parameter that defines the scale at which suppression occurs free and perform a Bayesian analysis, comparing with cosmic microwave background data. The data show a preference for some of the suppression to be within the observable window. Guided by this analysis, we choose concrete illustrative values for this parameter. We show that the model affects only slightly the parity anomaly, but it is capable of alleviating the lensing and power suppression anomalies.

Angular power spectra are central to the study of our Universe. In this paper, I develop a new method for the numeric evaluation and analytic estimation of the angular cross-power spectrum of two random fields using complex analysis and Picard-Lefschetz theory. The proposed continuous deformation of the integration domain resums the highly oscillatory integral into a convex integral whose integrand decays exponentially. This deformed integral can be quickly evaluated with conventional integration techniques. These methods can be used to quickly evaluate and estimate the angular power spectrum from the three-dimensional power spectrum for all angles (or multipole moments). This method is especially useful for narrow redshift bins, or samples with small redshift overlap, for which the Limber approximation has a large error.

In this work, we explore the low-energy effects induced from the integration of the heavy Higgs boson modes $H$, $A$, and $H^{\pm }$ within the two-Higgs-doublet model (2HDM) by assuming that the lightest Higgs boson $h$ is the one observed experimentally at $m_h\sim 125\mathrm{GeV}$. We work within the context of effective field theories, focusing on the Higgs effective field theory (HEFT), although some comparisons with the Standard Model effective field theory case are also discussed through this work. Our main focus is placed in the computation of the nondecoupling effects from the heavy Higgs bosons and the capture of such effects by means of the HEFT coefficients which are expressed in terms of the input parameters of the 2HDM. Our approach to solve this issue is by matching the amplitudes of the 2HDM and the HEFT for physical processes involving the light Higgs boson $h$ in the external legs instead of the most frequently used matching procedure at the Lagrangian level. More concretely, we perform the matching at the amplitudes level for the following physical processes, including scattering and decays: $h\to W{W}^{*}\to Wf\overline{f^{\prime }}$, $h\to Z{Z}^{*}\to Zf\overline{f}$, $WW\to hh$, $ZZ\to hh$, $hh\to hh$, $h\to \gamma \gamma$, and $h\to \gamma Z$. One important point of this work is that the matching is required to happen at low energies compared to the heavy Higgs boson masses, and these are heavier than the other particle masses. The proper expansion for this heavy mass limit is also defined here, which provides the results for the nondecoupling effects presented in this work. We finally discuss the implications of the resulting effective coefficients and remark on the interesting correlations detected among them.

We study a realistic SU(5) grand unified model, where a $\mathbf{45}$ representation of scalar fields is added to the Georgi-Glashow model in order to realize the gauge coupling unification and the masses and mixing of quarks and leptons. The gauge coupling unification together with constraints from proton decay implies mass splittings in scalar representations. We assume that an SU(2) triplet component of the $\mathbf{45}$ scalar, which is called $S_3$ leptoquark, has a TeV-scale mass, and color-sextet and color-octet ones have masses of the order of ${10}^6\mathrm{GeV}$. We calculate one-loop beta functions for Yukawa couplings in the model, and derive the low-energy values of the $S_3$ Yukawa couplings which are consistent with the grand unification. We provide predictions for lepton-flavor violation and lepton-flavor-universality violation induced by the $S_3$ leptoquark, and find that current and future experiments have a chance to find a footprint of our SU(5) model.

We explore the possibility of resolving simultaneously the $W$-boson mass shift reported by the CDF Collaboration and the apparent deviation from unitarity in the first row of the CKM mixing matrix in a class of left-right symmetric models. The fermion masses are generated in these models through a universal seesaw mechanism, utilizing vectorlike partners of the usual fermions. We find a unique solution to the two anomalies where the mixing of the down quark with a vectorlike quark (VLQ) resolves the CKM unitarity puzzle, and the mixing of the top quark with a VLQ partner explains the $W$ boson mass shift. The validity of this setup is tested against the stability of the Higgs potential up to higher energies. We find upper bounds of (4, 4) TeV on the masses of the top-partner VLQ, and a neutral scalar associated with $SU(2{)}_R$ gauge symmetry breaking, respectively. This class of models can solve the strong $CP$ problem via parity symmetry without the need for an axion.

The excitation spectra of ${\mathrm{\Lambda }}_c$ and ${\mathrm{\Lambda }}_b$ baryons are investigated by using a quark-diquark model in which a single-heavy baryon is treated as the bound state of a heavy quark and a scalar diquark. We take two types of relativistic corrections into account for the quark-diquark potential. In the first type, we consider the one-gluon exchange between the heavy quark and one of the light quarks in the diquark. In the second, we consider the one-gluon exchange between a scalar particle and a heavy quark. We find that there is a large difference between the two types of corrections due to different treatments of the internal color structure of the diquark. The relativistic corrections are important for the solution to the string tension puzzle, particularly, the Darwin term makes a large contribution.

We consider two-dimensional conformal field theories (CFTs) that exhibit a hallmark feature of quantum chaos: universal repulsion of energy levels as described by a regime of linear growth of the spectral form factor. This physical input together with modular invariance strongly constrains the spectral correlations and the subleading corrections to the linear growth. We show that these are determined by the Kuznetsov trace formula, which highlights an intricate interplay of universal physical properties of chaotic CFTs and analytic number theory. The trace formula manifests the fact that the simplest possible CFT correlations consistent with quantum chaos are precisely those described by a Euclidean wormhole in ${\mathrm{AdS}}_3$ gravity with $[\mathrm{torus}]\times [\mathrm{interval}]$ topology. For contrast, we also discuss examples of nonchaotic CFTs in this language.

A common way to avoid divergent integrals in homogeneous spatially noncompact gravitational systems, as e.g. cosmology, is to introduce a fiducial cell by cutting off the spatial slice at a finite region $V_o$. This is usually considered as an auxiliary integral regulator to be removed after performing computations by sending $V_o\to \infty$. In this paper, we analyze the dependence of the classical and quantum theory of homogeneous, isotropic, and spatially flat cosmology on this fiducial cell. We show that each fixed $V_o$ regularization leads to a different canonically independent theory. At the classical level, the dynamics of observables is not affected by the regularization choice on-shell. For the quantum theory, however, this leads to a family of regulator dependent quantum representations labeled by $V_o$, and the limit $V_o\to \infty$ becomes then more subtle. First, we construct a novel isomorphism between different $V_o$-regularizations, which allows us to identify states in the different $V_o$-labeled Hilbert spaces to ensure equivalent dynamics for any value of the regulator. The $V_o\to \infty$ limit would then correspond to choosing a state for which the volume assigned to the fiducial cell becomes infinite as appropriate in the late-time regime. As the second main result of our analysis, quantum fluctuations of observables smeared over subregions $V\subset V_o$, unlike those smeared over the full $V_o$, explicitly depend on the size of the fiducial cell through the ratio $V/V_o$ interpreted as the (inverse) number of subcells $V$ homogeneously patched together into $V_o$. Physically relevant fluctuations for a finite region, as e.g. in the early-time regime, which would be unreasonably suppressed in a naïve $V_o\to \infty$ limit, become appreciable at small volumes. Our results suggest that the fiducial cell is not playing the role of a mere regularization but is physically relevant at the quantum level and complements previous statements in the literature.

In this paper, we construct a hybrid boson star model composed of a complex scalar field and a Proca field. The scalar field and the Proca field are both in their ground state. The model is numerically solved to obtain families of solutions for different mixed states, considering both synchronized and nonsynchronized cases. By examining the relation between the ADM mass and the synchronized frequency $\tilde{\omega }$ or the nonsynchronized frequency ${\tilde{\omega }}_P$, we identify several types of solution families for the hybrid Proca-boson stars. In addition to solutions that intersect with the scalar field and the Proca field at each end, there are also several types of multibranch mixed-state solutions. The characteristics of various solutions are analyzed and discussed in detail. We calculate the binding energy $E$ of the hybrid Proca-boson stars and provide the relationship between $E$ and both the synchronized frequency $\tilde{\omega }$ and the nonsynchronized frequency ${\tilde{\omega }}_P$. Furthermore, we obtain the stability of the corresponding hybrid star solution families from the above analyses.

The theory of macroscopic gravity provides a formalism to average the Einstein field equations from small scales to largest scales in space-time. It is well known that averaging is an operation that does not commute with calculating the Einstein tensor and this leads to a correction term in the field equations known as backreaction. In this work, we derive exact solutions to the macroscopic gravity field equations assuming that the averaged geometry is plane or spherically symmetric, and the source is taken as vacuum, dust, or perfect fluid. We then focus on the specific cases of spherical symmetry and derive solutions that are analogous to the Schwarzschild, Tolman VII, and Lemaître-Tolman-Bondi solutions. The geodesic equations and curvature structure are contrasted with the general relativistic counterparts for the Schwarzschild and Lemaître-Tolman-Bondi solutions.

We study Bayesian inference of black hole ringdown modes for simulated binary black hole signals. We consider to what extent different fundamental ringdown modes can be identified in the context of black hole spectroscopy. Our simulated signals are inspired by the high-mass event GW190521. We find strong correlation between mass ratio and Bayes factors of the subdominant ringdown modes. The Bayes factor values and time dependency, and the peak time of the (3,3,0) mode align with those found analyzing the real event GW190521, particularly for high-mass ratio systems.

The ghost-free bimetric gravity theory is a viable theory of gravity that explores the interaction between a massless and a massive graviton and can be described in terms of two dynamical metrics. In this paper, we present an exact static, spherically symmetric vacuum solution within this theory. The solution is spatially Schwarzschild-de Sitter, with the value of the cosmological constant determined by the graviton mass and the interaction parameters of the theory. Notably, for specific parameter ranges, the solution represents a traversable Lorentzian wormhole that violates the weak energy condition near its throat. Furthermore, we have investigated the evolution of scalar and electromagnetic fields in this wormhole spacetime and observed the presence of arbitrarily long-lived quasiresonant modes in the quasinormal spectrum.

A stochastic gravitational wave background is a prediction of a number of astrophysical and cosmological phenomena including early Universe cosmology. Recently, the NANOGrav Collaboration reported conclusive evidence for a stochastic gravitational wave background. We analyze the NANOGrav signal, assuming it is of primordial origin, including the reheating phase. We use the latest measurements from NANOGrav to constrain the Universe’s reheating equation of state $w_{\mathrm{re}}$, the reheating temperature $T_{\mathrm{re}}$, the tensor-to-scalar ratio $r$, and the tensor tilt $n_t$. Assuming the constant equation of state $w_{\mathrm{re}}$ to be responsible for the reheating phase, we find a preference for instant reheating, $w_{\mathrm{re}}=0.36_{-0.28}^{+0.15}$, and a very blue tilt $n_t=1.94_{-0.88}^{+0.43}$. We find a degeneracy between the tensor-to-scalar ratio $r$ and $T_{\mathrm{re}}$ and suggest ways to break this degeneracy. In all cases where the reheating temperature is constrained, it is constrained to be very low, with $T_{\mathrm{re}}\le {10}^5\mathrm{GeV}$. We further find that a scale-invariant spectrum, as suggested by inflation, implies a stiff equation of state $w_{\mathrm{re}}=19/3$. If extrapolated, the blue-tilted primordial spectrum that agrees with the NANOGrav signal at corresponding frequencies is incompatible with the LIGO bound. This incompatibility is another challenge for connecting NANOGrav with the primordial spectrum. We discuss a number of ways to circumvent this issue. We split the spectrum into a sum of astrophysical and primordial spectra and constrain the astrophysical and primordial components using NANOGrav data and the LIGO bound. In another attempt, we use the same data and constrain the running of the spectrum. Any of these, or a combination of such methods, can be used to reconcile the NANOGrav data and the LIGO bound with the primordial power spectrum.

The cosmological principle is one of the fundamental assumptions of the standard model of cosmology (SCM), and it allows us to describe cosmic distances and clocks by using the Friedmann-Lemaître-Roberton-Walker (FLRW) metric. Thus, it is essential to test the FLRW metric with cosmological observations to verify the validity of the SCM. In this work, we perform tests of the FLRW metric by comparing the observational comoving angles between the Hubble $H(z)$ and the transversal baryon acoustic oscillation (BAO) measurements. The Gaussian process is employed to reconstruct the Hubble $H(z)$ measurements and the angular diameter distance (ADD) from the transversal BAO data. A nonparametric method is adopted to probe the possible deviations from the FLRW metric at any redshift by comparing the comoving distances from the reconstructed Hubble $H(z)$ measurements with the ADD reconstructed from the transversal BAO data. Then, we propose two types of parametrizations for the deviations from the FLRW metric, and test the FLRW metric by using the priors of specific sound horizon scales. To avoid the bias caused by the prior of a specific sound horizon scale, we perform the consistency test with a flat prior of the sound horizon scale. We find that there is a concordance between the FLRW metric and the observational data by using parametric and nonparametric methods, and the parametrizations can be employed to test the FLRW metric in a new way independent of the sound horizon scale.

We derive an analytic expression for the two-point correlation function in redshift space which (i) is nonlinear (ii) is valid on the full sky, i.e. the distant-observer limit is not assumed, (iii) can account for the effect of magnification and evolution bias due to a nonuniform selection function, and (iv) respects the fact that observations are made on the past light cone, so naturally yields unequal-time correlations. Our model is based on an exact treatment of the streaming model in the wide-angle regime. Within this general regime, we find that the redshift-space correlation function is essentially determined by a geometric average of its real-space counterpart. We show that the linear expression for the galaxy overdensity, accurate to subleading order, can be recovered from our nonlinear framework. This work is particularly relevant for the modeling of odd multipoles of the correlation function at small separations and low redshifts, where wide-angle effects, selection effects, and nonlinearities are expected to be equally important.

In this paper, we explore the chaotic signatures of the geodesic dynamics for particles moving in the slowly rotating Hartle-Thorne spacetime; an approximate solution of vacuum Einstein field equations describing the exterior of a massive, deformed, and slowly rotating compact object. We employ a numerical study to examine the geodesics of prolate and oblate deformations for generic orbits and find the plateaus of the rotation curve, which are associated with the existence of Birkhoff islands in the Poincaré surface of the section, where the ratio of the radial and polar frequency of geodesics remains constant throughout the island. We investigate various phase-space structures, including hyperbolic points and chaotic regions in the neighborhood of resonant islands. Moreover, chaotic behavior is observed to be governed by the stickiness phenomenon, where chaotic orbits remain attached to stable ones for an extended duration before eventually diverging and are attracted toward the surface of the neutron star. The precision of the numerical integration used to simulate the particle’s trajectories plays a crucial role in the structure of the Poincaré surface of the section. We present a comparison of several efficient structure-preserving numerical schemes of order four applied to the considered nonintegrable dynamical system and we investigate which schemes possess the canonical property of the Hamiltonian flow. In particular, we compare the performance of the symplectic Runge-Kutta integrator with the G-symplectic general linear method. Among the class of nonsymplectic integrators, we employ the explicit Runge-Kutta method and an explicit general linear method with a standard projection technique to project the numerical solution onto the desired manifold. The projection scheme admits the integration without any drift from the desired manifold and is computationally cost effective. We are concerned with two crucial aspects; long-term behavior and CPU time consumption.

The chiral and deconfinement phase transitions under rotation have been simultaneously investigated in the Polyakov-Nambu-Jona-Lasinio (PNJL) model. An interesting observation has been found that the chiral phase transition is catalyzed and the deconfinement phase transition is decelerated by rotation, therefore a chiral symmetric but confined phase is induced by rotation, which indicates that chiral dynamics and gluon dynamics can be split by rotation.

We revisit the change of the electric permittivity of the QED vacuum by a strong constant electric field, motivated by the analogy between the dynamically assisted Schwinger effect in strong-field QED and the Franz-Keldysh effect in semiconductor physics. We develop a linear-response theory based on the nonequilibrium in-in formalism and the Furry-picture perturbation theory. Applying the developed formalism and also utilizing the Kramers-Krönig relation, we calculate the electric permittivity for wide values of the field strength and the probe frequency, including the supercritical field and/or high probe frequency that the previous research has not fully covered. We discover that the electric permittivity exhibits a characteristic oscillating feature in the high probe-frequency regime, which directly reflects the change of the QED-vacuum structure by the strong field. We also establish a quantitative correspondence between the electric permittivity and the number of electron-positron pairs produced by the dynamically assisted Schwinger effect.

In this work, we attempt to answer the question, “What is the minimal viable renormalizable $SU(5)$ grand unified theory with representations no higher than adjoints?” We find that an $SU(5)$ model with a pair of vectorlike fermions $5_F+{\overline{5}}_F$, as well as two copies of $15_H$ Higgs fields, is the minimal candidate that accommodates for correct charged fermion and neutrino masses and can also address the matter-antimatter asymmetry of the Universe. Our results show that the presented model is highly predictive and will be fully tested by a combination of upcoming proton decay experiments, collider searches, and low-energy experiments in search of flavor violations. Moreover, we also entertain the possibility of adding a pair of vectorlike fermions $10_F+{\overline{10}}_F$ or $15_F+{\overline{15}}_F$ (instead of a $5_F+{\overline{5}}_F$). Our study reveals that the entire parameter space of these two models, even with minimal particle content, cannot be fully probed due to a possible longer proton lifetime beyond the reach of Hyper-Kamiokande.

Dark matter particles can form halos gravitationally bound to massive astrophysical objects. The Earth could have such a halo where depending on the particle mass, the halo either extends beyond the surface or is confined to the Earth’s interior. We consider the possibility that if dark matter particles are coupled to neutrinos, then neutrino oscillations can be used to probe an Earth dark matter halo. In particular, atmospheric neutrinos traversing the Earth can be sensitive to a small size, interior halo, inaccessible by other means. Depending on the halo mass and neutrino energy, constraints on the dark matter-neutrino couplings are obtained from the halo corrections to the neutrino oscillations.