One of the long-standing goals in the framework of inflation is the construction of tools that can be used to classify models in theory space. An idea that has been put forward in this context is to consider the energy-dependent scaling behavior of observables to characterize different models. We implement this approach in the framework of hilltop and hilltop-squared inflation by analyzing their observables when the small-field approximation is not imposed and the energy scale $\mu$ of these models is varied as a free parameter, subject to observational constraints. We show that the scalar spectral tilt and the tensor ratio $r$ exhibit $\mu$-dependent scaling behavior and that the scaling exponents as functions of $\mu$ in turn lead to functional forms that are model dependent. Scaling relations of the type discussed here are of interest as characteristics of the inflationary theory space as well as in the context of the postinflationary reheating process. We further observe a bifurcation behavior in the behavior of $p$-families in the spectral-tensor plane for a critical value of $\mu$.

The power spectrum and voxel intensity distribution (VID) are two summary statistics that can be applied to condense the information encoded in line-intensity maps. The information contained in both summary statistics is highly complementary, and their combination allows for a major increase in precision of parameter estimation from line-intensity mapping (LIM) surveys. Until recently, combination of these statistics required simulation-based estimations of their covariance. In this work we leverage an analytical model of covariance between these observables to run a joint Fisher forecast focusing on the CO(1-0) rotational line targeted by the COMAP survey and a wider, shallower hypothetical iteration. We consider a generalized phenomenological non-CDM model, models with axion dark matter, and local primordial non-Gaussianity, to highlight where a combined analysis of the power spectrum and VID can be most useful. Our results demonstrate improvements in sensitivity to beyond-$\mathrm{\Lambda }\mathrm{CDM}$ physics over analyses using either the power spectrum or VID on their own, by factors ranging from 2 to 50, showcasing the potential of joint analyses in unlocking new insights into fundamental physics with LIM surveys.

The vast majority of gravitational-wave signals from stellar-mass compact binary mergers are too weak to be individually detected with present-day instruments and instead contribute to a faint, persistent background. This astrophysical background is targeted by searches that model the gravitational-wave ensemble collectively with a small set of parameters. The traditional search models the background as a stochastic field and estimates its amplitude by cross-correlating data from multiple interferometers. A different search uses gravitational-wave templates to marginalize over all individual event parameters and measure the duty cycle and population properties of binary mergers. Both searches ultimately estimate the total merger rate of compact binaries and are expected to yield a detection in the coming years. Given the conceptual and methodological differences between them, though, it is not well understood how their results should be mutually interpreted. In particular, when a detection of an astrophysical compact binary background is claimed by either approach, which portion of the population is in fact contributing to this detection? In this paper, we use the Fisher information to study the implications of a background detection in terms of which region of the Universe each approach probes. Specifically, we quantify how information about the compact binary merger rate is accumulated by each search as a function of the event redshift. For the LIGO design sensitivity and a uniform-in-comoving-volume distribution of equal-mass $30M_{\odot }$ binaries, the traditional cross-correlation search obtains 99% of its information from binaries up to redshift 2.5 (average signal-to-noise ratio $<8$), and the template-based search from binaries up to redshift 1.0 (average signal-to-noise ratio $\sim 8$). While we do not calculate the total information accumulated by each search, our analysis emphasizes the need to pair any claimed detection of the stochastic background with an assessment of which binaries contribute to said detection. In the process, we also clarify the astrophysical assumptions imposed by each search.

We present a comprehensive study of compact stars admixed with nonself-annihilating self-interacting fermionic dark matter, delineating the dependence on the nuclear equation of state by considering the two limiting parametrized equations of state for neutron star matter obtained by smoothly matching the low-density chiral effective theory and the high-density perturbative QCD. These two parametrizations are the limiting cases of a wide variety of smooth equations of state, i.e., the softest and stiffest possible one without a phase transition, that generate masses and radii compatible with $2M_{\odot }$ observations and the tidal constraint from GW170817. With an exhaustive analysis of the possible stable mass-radius configurations, we determine the quantity of dark matter contained in stars with masses and radii compatible with the aforementioned astrophysical constraints. We find that for dark particle masses of a few tenths of GeV, the dark core collapses and no stable solutions are found for the two limiting ordinary matter equations of state. For lower masses, the dark matter fraction is limited to 10%, being at most 1% for masses ranging from 0.1 GeV to 10 GeV for the limiting soft nuclear equation of state. For the limiting stiff nuclear equation of state, the dark matter fraction can reach values of more than 10%, but the dark particle mass is being constrained to 0.3 GeV and 10 GeV for the weak self-interacting case and has to be at least 5 GeV for the strong self-interacting one. For dark particle masses of less than 0.1 GeV, stable neutron star configurations should have less than 1% of self-interacting dark matter to be compatible with the constraint of the tidal deformability from GW170817 for the two limiting ordinary matter equations of state studied.

The recent detection of gravitational waves from a binary neutron star merger event offers a unparalleled insight into the dense matter. Meanwhile, the existence of quark matter within neutron stars, potentially forming hybrid stars or even strange quark stars, and the possible presence of dark matter mixed within these compact stars remain a matter of debate. To address this, our study explores the inspiral processes of various binary compact star systems, including binary hybrid stars, binary strange quark stars, as well as their corresponding dark matter-mixed counterparts, to decode the signatures imprinted in inspiral gravitational waves. Our analysis reveals that the inspiral process of hybrid stars and strange quark stars exhibit higher gravitational wave frequencies and longer retarded times than that of traditional neutron stars. Mixing dark matter components into these systems further amplifies these signals, increasing the frequency and extending the inspiral duration even more. These findings highlight the critical roles of dark matter and quark matter in determining the features of inspiral gravitational waves, providing vital clues for future observations. Moreover, our study also suggests the use of inspiral gravitational waves can play an effective tool to decipher the signals of quark and dark matter within neutron stars.

Magnetic monopoles, if they exist, would be produced amply in strong magnetic fields via the Schwinger process. Such circumstances arise in neutron stars with a strong magnetic field—magnetars. It is argued in this article that pair production of magnetic monopoles in magnetars must be accompanied with hypothetical magnetic monopole noise. It is shown that magnetic monopole noise, if it exists, must have Poisson statistics and “white” spectrum. Magnetic monopole noise leads to magnetic field fluctuations, which may be related to spin period fluctuations of magnetar. Estimations show that such period fluctuations for sufficiently light magnetic monopoles, if they are produced in the magnetic field of magnetar, can be measured experimentally.

The proposed space gravitational-wave (GW) detector LISA has potential to detect stellar-mass binary black holes (BBHs). The majority of the detected BBHs are expected to emit nearly monochromatic GWs, whose frequency evolution will be efficiently described by Taylor expansions. We study the measurability of the associated time derivative coefficients of the frequencies, by extending a recent work based on a simplified Fisher matrix analysis. Additionally, we provide qualitative discussions on how to extract astrophysical information, such as orbital eccentricity and tertiary perturbation, from the observed derivative coefficients.

A system was recently implemented in the Virgo detector to cancel noise in its data produced by seismic waves directly coupling with the suspended test masses through gravitational interaction. The data from seismometers are being filtered to produce a coherent estimate of the associated gravitational noise also known as Newtonian noise. The first implementation of the system uses a time-invariant (static) Wiener filter, which is the optimal filter for Newtonian-noise cancellation assuming that the noise is stationary. However, time variations in the form of transients and slow changes in correlations between sensors are possible and while time-variant filters are expected to cope with these variations better than a static Wiener filter, the question is what the limitations are of time-variant noise cancellation. In this study, we present a framework to study the performance limitations of time-variant noise cancellation filters and carry out a proof of concept with adaptive filters on seismic data at the Virgo site. We demonstrate that the adaptive filters, at least those with superior architecture, indeed significantly outperform the static Wiener filter with the residual noise remaining above the statistical error bound.

Convergence of three different expansion schemes at finite baryon chemical potentials, including the conventional Taylor expansion, the Padé approximants, and the $T^{\prime }$ expansion proposed recently in lattice QCD simulations, have been investigated in a low energy effective theory within the functional renormalization group approach. It is found that the convergence of the $T^{\prime }$ expansion and the Padé approximants is consistent with the conventional Taylor expansion, within the expansion orders considered in this work. Furthermore, we find that the consistent regions of the three different expansions are in agreement with the convergence radius of the Lee-Yang edge singularities.

We critically assess to what extent it makes sense to bound the Wilson coefficients of dimension-six operators. In the context of Higgs physics, we establish that a closely related observable, $c_H$, is well defined and satisfies a two-sided bound. $c_H$ is derived from the low momentum expansion of the scattering amplitude, or the derivative of the amplitude at the origin with respect to the Mandelstam variable $s$, expressed as $M(H_i{H}_i\to H_j{H}_j)=c_{H}s+O(g_{\mathrm{SM}},s^{-2})$ where $g_{\mathrm{SM}}$ represents all Standard Model couplings. This observable is nondispersive and, as a result, not sign-definite. We also determine the conditions under which the bound on $c_H$ is equivalent to a bound on the dimension-six operator $O_H=\partial |H{|}^2\partial |H{|}^2$.

The standard model effective field theory (SMEFT) is a universal way of parametrizing new physics (NP) manifesting as new, heavy particle interactions with the Standard Model (SM) degrees of freedom, that respect the SM gauged symmetries. Higher order terms in the NP interactions possibly lead to sizable effects, mandatory for meaningful phenomenological studies, such as contributions to neutral meson mixing, which typically pushes the scale of NP to energy scales much beyond the reach of direct searches in colliders. I discuss the leading-order renormalization of double-insertions of dimension-6 four-fermion operators that change quark flavor by one unit (i.e., $|\mathrm{\Delta }F|=1$, $F=\mathrm{strange}$-, charm-, or bottom-flavor), by dimension-8 operators relevant to meson mixing (i.e., $|\mathrm{\Delta }F|=2$) in SMEFT. Then, I consider the phenomenological implications of contributions proportional to large Yukawas, setting bounds on the Wilson coefficients of operators of dimension-6 via the leading logarithmic contributions. Given the underlying interest of SMEFT to encode full-fledged models at low energies, this work stresses the need to consider dimension-8 operators in phenomenological applications of dimension-6 operators of SMEFT.

Inspired by the recent report from the LHCb Collaboration on $T_{cc}$, which can be interpreted as a molecular $D{D}^{*}$, we investigated two trimeson systems of the $T_{cc}$ partner with $I{J}^P=01^{-}$ in the framework of a chiral quark model. In the first case, because of the attraction between $D^{*}$ and $\overline{D}$, we explored the existence of bound states in the system $D^{*}D\overline{D}$, which is obtained by adding $\overline{D}$ into the molecular bound state $T_{cc}$ ($D{D}^{*}$). Similarly, in the second case, we explored whether there is a bound state in the $D^{*}DK$ system, which is obtained by adding $K$ into the $T_{cc}$, given the attraction between $D$ and $K$. The results show that both of them are bound states, in which the binding energy of the molecular state $D{D}^{*}K$ is relatively small, only $0.4\pm 0.4\mathrm{MeV}$, while the binding energy of $D{D}^{*}\overline{D}$ is up to $1.6\pm 0.3\mathrm{MeV}$. According to the calculation results of the root-square-mean distances, the spatial structure of the two systems shows the obvious $(D{D}^{*})\text{−}(\overline{D}/K)$ structure, in which $D$ is close to $D^{*}$ while $D{D}^{*}$ as a whole is relatively distant from the third hadron ($\overline{D}/K$), which are similar to the nucleon-electron structure. As a result, we strongly recommend that these bound states $D{D}^{*}\overline{D}$ and $D{D}^{*}K$ are searched for experimentally.

It is commonly understood that the strong magnetic field produced in heavy ion collisions is short-lived. The electric conductivity of the quark-gluon plasma is unable to significantly extend the lifetime of the magnetic field. We propose an alternative scenario to achieve this: with finite baryon density and spin polarization by the initial magnetic field, the quark-gluon plasma behaves as a paramagnet, which may continue to polarize the quark after fading of the initial magnetic field. We confirm this picture by calculations in both quantum electrodynamics and quantum chromodynamics. In the former case, we find a splitting in the damping rates of probe fermions with an opposite spin component along the magnetic field. In the latter case, we find a similar splitting in damping rate of the probe quark in quark-gluon plasma in both high and low density limits. The splitting provides a way of polarizing strange quarks by the quark-gluon plasma paramagnet consisting of light quarks, which effectively extends the lifetime of the magnetic field in heavy ion collisions.

We establish robust relations between Transverse Momentum Dependent distributions (TMDs) and collinear distributions. We define weighted integrals of TMDs that we call Transverse Momentum Moments (TMMs) and prove that TMMs are equal to collinear distributions evaluated in some minimal subtraction scheme. The conversion to the modified minimal subtraction ($\overline{\mathrm{MS}}$) scheme can be done by a calculable factor, which we derive up to three loops for some cases. We discuss in detail the zeroth, the first, and the second TMMs and provide phenomenological results for them based on the current extractions of TMDs. The results of this paper open new avenues for theoretical and phenomenological investigation of the three-dimensional and collinear hadron structures.

We show that supplementing the Standard Model by only a second Higgs doublet, a combined explanation of $h\to e\tau$, $h\to \mu \tau$, $b\to s{\ell }^{+}{\ell }^{-}$, the $W$ mass and $R(D^{(*)})$ as well as the excess in $t\to b{H}^{+}(130\mathrm{GeV})\to b\overline{b}c$ is possible. While this requires flavor violating couplings, the stringent bounds from, e.g., $\mu \to e\gamma$, $\tau \to \mu \gamma$, $B_s-{\overline{B}}_s$ mixing, $b\to s\gamma$, low mass dijet, and $pp\to H^{+}{H}^{-}\to {\tau }^{+}{\tau }^{-}\nu \overline{\nu }$ searches can be avoided. However, the model is very constrained; it inevitably predicts a shift in the SM Higgs coupling strength to tau leptons as well as a nonzero $t\to hc$ rate, as indeed preferred by recent measurements. We study three benchmark points providing such a simultaneous explanation and calculate their predictions, including collider signatures which can be tested with upcoming LHC run-3 data.

In the bestest little Higgs model (BLHM) scenario, we analyze the branching ratios and production cross section of the heavy Higgs boson $H_0$. The analysis is performed at the tree level and the one-loop level. In addition, we present results of the possible production of the heavy Higgs boson $H_0$ via gluon fusion for the center-of-mass energies and integrated luminosities of the LHC, HE-LHC, and HL-LHC. Our results show a very optimistic scenario for studying the $H_0$ scalar predicted by the BLHM and for the energies and luminosities of current and future hadron colliders.

We investigate the collision dynamics of $U(1)$ gauged $Q$-balls by performing high-resolution numerical simulations in axisymmetry. Focusing on the case of relativistic head-on collisions, we consider the effects of the initial velocity, relative phase, relative charge, and electromagnetic coupling strength on the outcome of the collision. We find that the collision dynamics can depend strongly on these parameters; most notably, electromagnetic effects can significantly alter the outcome of the collision when the gauge coupling is large. When the gauge coupling is small, we find that the dynamics generally resemble those of ordinary (nongauged) $Q$-balls.

Beyond the Standard Model electromagnetic properties of neutrinos may lead to copious production of sterile neutrinos in the hot and dense core of a core-collapse supernova. In this work, we focus on the active-sterile transition magnetic moment portal for heavy sterile neutrinos. Firstly, we revisit the SN1987A cooling bounds for dipole portal using the integrated luminosity method, which yields more reliable results (especially in the trapping regime) compared to the previously explored via emissivity loss, also known as the Raffelt criterion. Secondly, we obtain strong bounds on the dipole coupling strength reaching as low as ${10}^{-11}{\mathrm{GeV}}^{-1}$ from energy deposition, i.e., constrained from the observation of explosion energies of underluminous Type IIP supernovae. In addition, we find that sterile neutrino production from Primakoff upscattering off of a proton dominates over scattering off of an electron for low sterile neutrino masses.