We consider the effect of density dependent dark matter on the neutron star mass, radius, and tidal deformability. Nuclear matter (normal matter) as well as the fermionic dark matter sector is considered in a mean field model. We adopt the two fluid formalism to investigate the effect of dark matter on the neutron star properties. In the two fluid picture, there is no direct interaction between the dark matter and the nuclear matter. Rather these two sectors interact only through gravitational interaction. The nuclear matter sector is described by the $\sigma -\omega -\rho$ meson interaction in the “FSU2R” parametrization. In the dark matter sector, we use the Bayesian parameter optimization technique to fix the unknown parameters in the dark matter equation of state. In the two fluid picture, we solve the coupled Tolman-Oppenheimer-Volkoff (TOV) equations to obtain the mass and radius of dark matter admixed neutron stars (DANSs). We also estimate the effect of the density dependent dark matter sector on the tidal deformability of dark matter admixed neutron stars (DANSs).

Time-delay interferometry (TDI) is a data processing technique for LISA designed to suppress the otherwise overwhelming laser noise by several orders of magnitude. It is widely believed that TDI can only be applied once all phase or frequency measurements from each spacecraft have been synchronized to a common time frame. We demonstrate analytically, using as an example the commonly used Michelson combination $X$, that TDI can be computed using the raw, unsynchronized data, thereby avoiding the need for an initial synchronization processing step and significantly simplifying the initial noise reduction pipeline. Furthermore, the raw data are free of any potential artifacts introduced by clock synchronization and reference frame transformation algorithms, which allow one to operate directly on the megahertz beatnotes. As a consequence, in-band clock noise is directly suppressed as part of TDI, in contrast to the approach previously proposed in the literature (in which large trends in the beatnotes are removed before the main laser-noise reduction step, and clock noise is suppressed in an extra processing step). We validate our algorithm with full-scale numerical simulations that use lisa instrument and pytdi and show that we reach the same performance levels as the previously proposed methods, ultimately limited by the clock sideband stability.

Nonlinear field theories produce unstable but long-lived configurations known as oscillons. These structures have been studied with asymmetric and symmetric double-well potentials and extended to other forms of potentials. In the present work, we examine the consequences of considering higher-order field theories, where we have used a generalization of the symmetric double-well potential and a ${\varphi }^6$ potential. Consequently, we have found $3+1$ spherically symmetric oscillons with significantly large lifetimes without parameter fine-tuning.

In the $\mathrm{SU}(3{)}_{\mathrm{F}}$ symmetry limit, using two- and three-particle distribution amplitudes of $B^{\pm }$-meson for $B_s$, the transition form factors of semileptonic $B_s\to K_0^{*}(1430)$ decays are calculated in the framework of the light-cone sum rules. The two-particle distribution amplitudes, ${\phi }_{+}(\omega )$ and ${\phi }_{-}(\omega )$ have the most important contribution in estimation of the form factors $f_{+}(q^2)$, $f_{-}(q^2)$, and $f_T(q^2)$. The knowledge of the behavior of ${\phi }_{+}(\omega )$ is still rather limited. Therefore, we consider three different parametrizations for the shapes of ${\phi }_{+}(\omega )$ that are derived from the phenomenological models. Using the form factors $f_{+}$, $f_{-}$, and $f_T$, the semileptonic $B_s\to K_0^{*}(1430)l\overline{{\nu }_l}$ and $B_s\to K_0^{*}(1430)l\overline{l}/\nu \overline{\nu }$, $l=e$, $\mu$, $\tau$ decays are analyzed. The branching fractions for the aforementioned decays, in addition the longitudinal lepton polarization asymmetries are calculated. A comparison between our results with predictions of other approaches is provided.

We present the explicit expressions of different pseudogauge transformations for Dirac and Proca fields considering a general interaction term. The particular case of the interaction of Dirac and Proca fields with a background electromagnetic field is also studied. Starting from the quantum kinetic theory with collisions derived from the Wigner-function formalism for massive spin-$1/2$ and spin-1 particles, we establish a connection between different pseudogauges and relativistic spin hydrodynamics. The physical implications of the various decompositions of orbital and spin angular momentum are discussed.

We use the Hamiltonian formulation of kinetic theory to perform a stability analysis of nonthermal fixed points in a non-Abelian plasma. We construct a perturbative expansion of the Fokker-Planck collision kernel in an adiabatic approximation and show that the (next-to-)leading order solutions reproduce the known nonthermal fixed point scaling exponents. Working at next-to-leading order, we derive the stability equations for scaling exponents and find the relaxation rate to the nonthermal fixed point. This approach provides the basis for an understanding of the prescaling phenomena observed in QCD kinetic theory and nonrelativistic Bose gas systems.

We reconsider the case of light vectors coupled to anomalous fermionic currents, focusing on the interplay between ultraviolet and infrared dynamics. Taking as a general framework the gauging of the Standard Model accidental symmetries, we show that it is possible to devise an anomaly-free ultraviolet completion with mostly chiral heavy fermions such that anomalous Wess-Zumino terms are suppressed in the infrared, thus relaxing would-be strong bounds from the longitudinal emission of light vectors coupled to nonconserved currents. We classify such scenarios and show that they will be extensively probed at the high-luminosity phase of the LHC via the measurement of the $h\to Z\gamma$ rate and the direct search for nondecoupling charged leptons.

The modification of the $\varphi$ meson spectrum in nuclear matter is studied in an updated QCD sum rule analysis, taking into account recent improvements in properly treating the chiral invariant and breaking components of four-quark condensates. Allowing both mass and decay width to change at finite density, the QCD sum rule analysis determines certain combinations of changes for these parameters that satisfy the sum rules equally well. A comprehensive error analysis, including uncertainties related to the behavior of various condensates at linear order in density, the employed renormalization scale and perturbative corrections of the Wilson coefficients, is used to compute the allowed ranges of these parameter combinations. We find that the $\varphi$ meson mass shift in nuclear matter is especially sensitive to the strange sigma term ${\sigma }_{sN}$, which determines the decrease of the strange quark condensate in nuclear matter. Specifically, we obtain a linear relation between the width ${\mathrm{\Gamma }}_{\varphi }$ and mass shift $\mathrm{\Delta }{m}_{\varphi }$ given as ${\mathrm{\Gamma }}_{\varphi }=a\mathrm{\Delta }{m}_{\varphi }+b{\sigma }_{sN}+c$ with $a=({3.947}_{-0.130}^{+0.139})$, $b=({0.936}_{-0.177}^{+0.180})$ and $c=-({7.707}_{-5.679}^{+4.791})\mathrm{MeV}$.

We compute the isolated photon production in association with a charged hadron at midrapidity in $pp$ and $pA$ based on the Color Glass Condensate (CGC) framework of high energy Quantum Chromodynamics (QCD) where, for the first time, we incorporate the Sudakov effect of soft gluon emissions. Our results are based on the leading order $qg\to q\gamma$ channel in the CGC framework and confronted with the recent data from Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) concerning the angular distributions and out-of-plane transverse momentum distributions. We find that, while the CGC computation alone results in too narrow distributions, with the help of the Sudakov effect, we can get a satisfactory description of the data. With this as a benchmark, we provide predictions for the magnitude of the nuclear effect brought by the phenomena of gluon saturation in the CGC.

We employ Riesz’s fractional derivative into the Wheeler-DeWitt (WDW) equation for a closed de Sitter geometry and obtain the no-boundary and tunneling wave functions. From the corresponding probability distributions, the event horizon of the nucleated universe can be a fractal surface with dimensions between $2\le D<3$. Concretely, the tunneling wave function favors fractal dimensions less than 2.5 and an accelerated power-law phase. Differently, the no-boundary proposal conveys fractal dimensions close to 3, with the universe instead entering a decelerated phase. Subsequently, we extend our discussion toward (nontrivial compact) flat and open scenarios. Our results suggest that given the probability of creation of a closed inflationary universe in the tunneling proposal is exponentially suppressed, a flat or an open universe becomes favored within fractional inflationary quantum universe.

We derive new positivity bounds for low-energy effective field theories (EFTs) that are not invariant under Lorentz boosts. “Positivity bounds” are the low-energy manifestation of certain fundamental properties in the UV—to date, they have been used to constrain a wide variety of EFTs; however, since existing bounds require Lorentz invariance they are not directly applicable when this symmetry is broken, such as for most cosmological and condensed matter systems. Assuming that the low-energy degrees of freedom can be extended into the UV in a way consistent with the fundamental axioms of unitarity, analyticity, and locality, we derive an infinite family of bounds that (derivatives of) the $2\to 2$ EFT scattering amplitude must satisfy even when Lorentz boosts are broken. We apply these bounds to the leading-order EFT of both a superfluid and the scalar fluctuations produced during inflation, comparing in the latter case with the current observational constraints on primordial non-Gaussianity, demonstrating that these bounds open a new window into the high-energy physics that lies beneath our low-energy measurements.

Classically, the inner horizon of a perturbed, rotating black hole undergoes an instability known as mass inflation, wherein the spacetime curvature diverges as a result of hyperrelativistic crossing streams of ingoing and outgoing radiation. The generic outcome of this instability is currently believed to be a strong, spacelike singularity, potentially alongside a weak, null singularity surviving at late times. However, the quantum backreaction in this regime has yet to be fully calculated for a realistic black hole spacetime. Here we consider a massless quantized scalar field $\varphi$ over the inflationary Kasner spacetime, a recently developed model for the inner horizon geometry of a rotating, accreting black hole. With this spacetime, we use numerical adiabatic regularization to calculate $⟨{\varphi }^2{⟩}_{\mathrm{ren}}$, the renormalized coincidence limit of the two-point correlation function, as a pointer to the behavior of the quantum stress-energy tensor. $⟨{\varphi }^2{⟩}_{\mathrm{ren}}$ is generically found to be nonzero near the inner horizon, divergent where the curvature classically diverges, and larger for smaller black hole spins or accretion rates.

We consider the classical static soliton solutions of the Skyrme model with false vacuum potential. We make use of fully three-dimensional relaxation calculations to construct global energy minimizers in the sectors of topological degrees from $Q=1$ to $Q=6$. These solutions may be metastable, they contain a domain of true vacuum inside the core. Further, we explore small regions of negative topological charge density which appear for the Skyrmions of degrees $Q=3$, 5, 6.

We use neutron star mass and radius measurements to constrain the spontaneous scalarization phenomenon in scalar-tensor theories using Bayesian analysis. Neutron star structures in this scenario can be significantly different from the case of general relativity, which can be used to constrain the theory parameters. We utilize this idea to obtain lower bounds on the coupling parameter $\beta$ for the case of massless scalars. These constraints are currently weaker than the ones coming from binary observations, and they have relatively low precision due to the approximations in our method. Nevertheless, our results clearly demonstrate the power of the mass-radius data in testing gravity, and can be further improved with future observations. The picture is different for massive scalars, for which the same data is considerably less effective in constraining the theory parameters in an unexpected manner. We identify the main reason for this to be a large high-likelihood region in the parameter space where deviations from general relativity are relatively small. We hope this initial study to be an invitation to use neutron star structure measurements more commonly to test alternative theories in general.

Measuring the quasinormal mode (QNM) spectrum emitted by a perturbed black hole (BH)—also known as BH spectroscopy—provides an excellent opportunity to test the predictions of general relativity in the strong-gravity regime. We investigate the prospects and precision of BH spectroscopy in massive binary black hole ringdowns, one of the primary science objectives of the future Laser Interferometric Space Antenna (LISA) mission. We simulate various massive binary BH population models, featuring competing prescriptions for the delays between galaxy and BH mergers, for the impact of supernova feedback on massive BH growth, and for the initial population of high redshift BH seeds (light versus heavy seeds). For each of these scenarios, we compute the average number of expected events for precision BH spectroscopy using a Fisher-matrix analysis. We find that, for any heavy seed scenario, LISA will measure the dominant mode frequency within $\mathcal{O}(0.1)\%$ relative uncertainty and will estimate at least three independent QNM parameters within 1% error. The most optimistic heavy seed scenarios produce $\mathcal{O}(100)$ events with 1% measurability for three or more QNM quantities during LISA’s operational time. On the other hand, light seed scenarios produce lighter merger remnants, which ring at frequencies higher than LISA’s sensitivity. Interestingly, the light seed models give rise to a fraction of mergers in the band of the Einstein Telescope, allowing for the measurement of three QNM parameters with $\sim 10\%$ relative errors in approximately a few to ten events/year. More precise BH spectroscopy in the light seed scenarios would require instruments operating in the decihertz band.

We study the impact of large lepton flavor asymmetries on the cosmic QCD transition. Scenarios of unequal lepton flavor asymmetries are observationally almost unconstrained and therefore open up a whole new parameter space for the cosmic QCD transition. We find that for large asymmetries, the formation of a Bose-Einstein condensate of pions can occur and identify the corresponding parameter space. In the vicinity of the QCD transition scale, we express the pressure in terms of a Taylor expansion with respect to the complete set of chemical potentials. The Taylor coefficients rely on input from lattice QCD calculations from the literature. The domain of applicability of this method is discussed.

The possibility of achieving quantum communication using photons across interstellar distances is examined. For this, different factors are considered that could induce decoherence of photons, including the gravitational field of astrophysical bodies, the particle content in the interstellar medium, and the more local environment of the Solar System. The x-ray region of the spectrum is identified as the prime candidate to establish a quantum communication channel, although the optical and microwave bands could also enable communication across large distances. Finally, we discuss what could be expected from a quantum signal emitted by an extraterrestrial civilization, as well as the challenges for the receiver end of the channel to identify and interpret such signals.

Tidal effects in gravitational-wave (GW) observations from binary neutron star mergers have the potential to probe ultradense matter and shed light on the unknown nuclear equation of state of neutron stars. Tidal effects in inspiralling neutron star binaries become relevant at GW frequencies of a few hundred Hz and require detectors with exquisite high-frequency sensitivity. Third generation GW detectors such as the Einstein Telescope or Cosmic Explorer will be particularly sensitive in this high-frequency regime, allowing us to probe neutron star tides beyond the adiabatic approximation. Here we assess whether dynamical tides can be measured from a neutron star inspiral. We find that the measurability of dynamical tides depends strongly on the neutron star mass and equation of state. For a semirealistic population of 10,000 inspiralling binary neutron stars, we conservatively estimate that on average $\mathcal{O}(50)$ binaries will have measurable dynamical tides. As dynamical tides are characterized not only by the star’s tidal deformability but also by its fundamental ($f$-) mode frequency, they present a possibility of probing higher-order tidal effects and test consistency with quasiuniversal relations. For a GW170817-like signal in a third generation detector network, we find that the stars’ $f$-mode frequencies can be measured to within a few hundred Hz.

In hadron physics, molecular-like multihadron states can interact with compact multiquark states. The latter are modeled as bare states in the Hilbert space of a potential model. In this work, we study several potential models relevant to the bare state, and solve their inverse scattering problems. The first model, called “cc,” is a separable potential model. We show that it can approximate (single-channel short-range) $S$-wave near-threshold physics with an error of $\mathcal{O}({\beta }^3/M_V^3)$, where $\beta$ sets the maximum momentum of the near-threshold region and $M_V$ is the typical scale of the potential. The second model, called “bc,” serves as the bare-state-dominance approximation, where interaction between continuum states is ignored. Under this model, even though the bare state is always crucial for a bound state’s generation, a shallow bound state naturally tends to have a small bare-state proportion. Therefore, we need other quantities to quantify the importance of the bare state. The last model, called “bcc,” is a combination of the first two models. This model not only serves as a correction to the bare-state-dominance approximation, but can also be used to understand the interplay between quark and hadron degrees of freedom. This model naturally leads to the presence of a Castillejo-Dalitz-Dyson (CDD) zero. We consider the energy decomposition of a bound state. The potential ratio of the bare-continuum interaction to the continuum self-interaction is proposed to understand how the bound state is generated. Model independently, an inequality for the potential ratio is derived. Based on the model “bcc,” the CDD zero can be used to estimate the potential ratio. Finally, we apply these studies to the deuteron, $\rho$ meson, and $D_{s0}^{*}(2317)$, and analyze their properties.

The effects on the speed of sound in neutron stars due to the presence of hyperons and a phase transition to deconfined quark matter is investigated. For this purpose a composite description within the covariant field theory is used; it consists of different models for the hadronic and for the unbound quark configurations. A phase transition with continuous and monotonous variation of the equation of state is assumed. The predictions obtained are contrasted with recent observational data on isolated neutron stars as well as on binary systems. Only one candidate is finally obtained from six different descriptions. According to the present calculations, the onset of the hyperons causes the equilibrium speed of sound to exceed the conformal limit. Based on recent works on the propagation of g-modes in neutron stars, different definitions of the speed of sound are considered.