Ultracompact minihalo (UCMH) is a special type of dark matter halo with a very steep density profile that may form in the early Universe seeded by an overdense region or a primordial black hole. Constraints on its abundance give valuable information on the power spectrum of primordial perturbation. In this work, we update the constraints on the UCMH abundance in the Universe using the extragalactic gamma-ray background observation. Comparing to previous works, we adopt the updated Fermi-LAT extragalactic gamma-ray background measurement and derive constraints based on a full consideration of the astrophysical contributions. With these improvements, we place constraints on UCMH abundance 1–2 orders of magnitude better than previous results. With the background components considered, we can also attempt to search for possible additional components beyond the known astrophysical contributions.

Fluctuating atmospheric emission is a dominant source of noise for ground-based millimeter-wave observations of the cosmic microwave background (CMB) temperature anisotropy at angular scales $\gtrsim 0.5°$. We present a model of the atmosphere as a discrete set of emissive turbulent layers that move with respect to the observer with a horizontal wind velocity. After introducing a statistic derived from the time-lag dependent correlation function for detector pairs in an array, referred to as the pair-lag, we use this model to estimate the aggregate angular motion of the atmosphere derived from time-ordered data from the Atacama Cosmology Telescope (ACT). We find that estimates derived from ACT’s CMB observations alone agree with those derived from satellite weather data that additionally include a height-dependent horizontal wind velocity and water vapor density. We also explore the dependence of the measured atmospheric noise spectrum on the relative angle between the wind velocity and the telescope scan direction. In particular, we find that varying the scan velocity changes the noise spectrum in a predictable way. Computing the pair-lag statistic opens up new avenues for understanding how atmospheric fluctuations impact measurements of the CMB anisotropy.

The purpose of mitigating all potential effects that can detrimentally influence the sensitivity of present and future gravitational wave detectors has triggered specific research and development worldwide. One of the many issues to be solved is the noise induced by the electrostatic charge forming on test mass mirrors. At LIGO, a mitigation method has been proposed, studied, and successfully applied. This method requires long mirror’s exposures to a relatively high pressure of ${\mathrm{N}}_2$ ions flux. It is difficult, if not impossible, to apply this method, the way it is now, when mirrors are at cryogenic temperatures, since a significantly thick condensed gas layer will develop on the mirror surface severely affecting its performance. Hence, we suggest a new method to neutralize test masses electrostatic charge that could be performed in ultra high vacuum (UHV) and could easily be applied to cryogenic mirrors. We suggest the use of selected energy electrons (between 10 to 100 eV) which, at very low doses, can impinge on the surface mirror. The energy of the incident beam can be tuned to neutralize positive and negative charges on the mirror’s dielectric surface or part of it. Here, we experimentally prove that this is successful in the case of Si and ${\mathrm{SiO}}_2$, two prototypical materials for mirror surfaces. The method is briefly presented in its basic principles, and a number of further studies are identified in view of developing the appropriate enabling technology.

Three current models of QCD in ($1+1$) dimensions are examined and extended in light-front coordinates. A pion of high momentum is found to have an infinite extent along its direction of motion.

We study the central production of QCD instantons at hadron colliders in events with two large rapidity gaps. These gaps in rapidity are formed by either Pomeron or photon exchanges or a combination of the two. The $k_T$-factorization formalism is used to reduce the factorization scale dependence. We compute for the first time the relevant differential cross sections for a complete set of central instanton production processes at the LHC, including gluon-induced and quark-induced amplitudes, and also show that the largest contribution comes from processes with Pomeron exchanges where a single gluon from each Pomeron couples to the instanton.

Leptoquark (LQ) models can be the solution to the $(g-2{)}_{\mu }$ anomaly because of their chiral enhancements. In this work, we consider the models extended by the LQ and vectorlike quark (VLQ) simultaneously, which can be used to explain the anomaly because of the top quark and top partner (denoted as $T$) mixing. For the one-LQ and one-VLQ extended models, there are contributions from the top and $T$ quarks. In the minimal LQ models, only the $R_2$ and $S_1$ representations can lead to the chiral enhancements. Here, we find one new $S_3$ solution to the anomaly in the presence of a $(X,T,B{)}_{L,R}$ triplet. We also consider the one-LQ and two-VLQ extended models, which can solve the anomaly even in the absence of top interactions and mixings. Then, we propose new LQ search channels under the constraints of $(g-2{)}_{\mu }$. Besides the traditional $t\mu$ decay channel, the LQ can also decay into $T\mu$ final states, which will lead to the characteristic multitop and multimuon signals at hadron colliders.

In this paper, decay widths of the doubly heavy baryons (${\mathrm{\Xi }}_{cc}$ and ${\mathrm{\Xi }}_{bc}$) production are theoretically calculated in the whole phase space through $W^{+}\to {\mathrm{\Xi }}_{cc}+\overline{c}+\overline{s}$ and $W^{+}\to {\mathrm{\Xi }}_{bc}+\overline{b}+\overline{s}$, within the framework of nonrelativistic QCD (NRQCD). Differential widths $d\mathrm{\Gamma }/d{s}_{12}$, $d\mathrm{\Gamma }/d{s}_{23}$, $d\mathrm{\Gamma }/d\cos {\theta }_{12}$, and $d\mathrm{\Gamma }/d\cos {\theta }_{13}$ are also given. In addition to the ordinary S-wave contributions for the baryons, we specifically calculate P-wave contributions as a comparison, namely the high excited states of the intermediate diquark, including $[{{}^{1}P}_1]$ and $[{{}^{1}P}_J]$ (with $J=0,1,2$) in both color antitriplet state $\overline{\mathbf{3}}$ and color sextuplet state $\mathbf{6}$. It shows that the contribution from the P-wave is about one order lower than the S-wave. According to the results, we can expect plentiful events produced at the LHC, i.e., $3.69\times {10}^5{\mathrm{\Xi }}_{cc}$ events and $4.91\times {10}^4{\mathrm{\Xi }}_{bc}$ events per year.

We propose to study the multiparticle configurations of isovector scalar mesons, $a_0(980)$ and $a_0(1450)$, in the charmless three-body $B$ decays by considering the width effects. Two scenarios of $a_0$ configurations are assumed in which the first one takes $a_0(980)$ as the lowest-lying $q\overline{q}$ state and $a_0(1450)$ as the first radial excited state, the second one takes $a_0(1450)$ as the lowest-lying $q\overline{q}$ state and $a_0(1950)$ as the first radial excited state while $a_0(980)$ is not a $q\overline{q}$ state. Within these two scenarios, we do the perturbative QCD (PQCD) calculation for the quasi-two-body $B\to a_0[\to K\overline{K}/\pi \eta ]h$ decays and extract the corresponding branching fractions of two-body $B\to a_{0}h$ decays under the narrow width approximation. Our predictions show that the first scenario of the $a_0(980)$ configuration cannot be excluded by the available measurements in $B$ decays, and the contributions from $a_0(1450)$ to the branching fractions in most channels are comparable in the first and second scenarios. Several channels are suggested for the forthcoming experimental measurements to reveal the multiparticle configurations of $a_0$, such as the channel $B^0\to a_0^{-}(980)[\to {\pi }^{-}\eta ]{\pi }^{+}$ with the largest predicted branching fraction, the channels $B^0\to a_0^{\pm }(1450)[\to K^{\pm }{\overline{K}}^0,{\pi }^{\pm }\eta ]{\pi }^{\mp }$ whose branching fractions obtained in the second scenario is about three times larger in magnitude than that obtained in the first scenario, and also the channels $B^{+}\to a_0^{+}(1950)[K^{+}{\overline{K}}^0/{\pi }^{+}\eta ]K^0$ whose branching fractions are linearly dependent on the partial width ${\mathrm{\Gamma }}_{a_0(1950)\to KK/\pi \eta }$.

We consider the theory of Rarita-Schwinger field interacting with a field with spin $1/2$, in the case of finite temperature, chemical potential and vorticity, and calculate the chiral vortical effect for spin $3/2$. We have clearly demonstrated the role of interaction with the spin $1/2$ field, the contribution of the terms with which to CVE is 6. Since the contribution from the Rarita-Schwinger field is $-1$, the overall coefficient in CVE is $6-1=5$, which corresponds to the recent prediction of a gauge chiral anomaly for spin $3/2$. The obtained values for the coefficients ${\mu }^2$ and $T^2$ are proportional to each other, but not proportional to the spin, which indicates a possible new universality between the temperature-related and the chemical potential-related vortical effects. The results obtained allow us to speculate about the relationship between the gauge and gravitational chiral anomalies.

We investigate the Page curve for a nonstandard black hole which is asymptotically nonflat/AdS/dS. For this purpose, we apply the island prescription to the charged linear dilaton black holes and analyze, in detail, the entanglement entropy of Hawking radiation for both the nonextremal case and the extremal case. In the nonextremal case, we find the Page curve consistent with the unitarity principle: at early times the entanglement entropy grows linearly in time without the island and at late times it saturates to double of the Bekenstein-Hawking entropy in the presence of the island. We observe the Page time is universal for all different models studied by our method: $t_{\text{Page}}=\frac{3}{\pi c}\frac{S_{\mathrm{BH}}}{T_H}$. For the extremal case, the island prescription provides the well-defined entanglement entropy only with the island, which cannot be obtained from the continuous limit of the nonextremal case. This implies that the Page curve may not be reproduced for the extremal case and further investigation is needed.

We study the complexity for an open quantum system. Our system is a harmonic oscillator coupled to a one-dimensional massless scalar field, which acts as the bath. Specifically, we consider the reduced density matrix by tracing out the bath degrees of freedom for both regular and inverted oscillators and compute the complexity of purification (COP) and complexity by using the operator-state mapping. We find that when the oscillator is regular, the COP saturates quickly for both underdamped and overdamped oscillators. Interestingly, when the oscillator is underdamped, we discover a kink-like behavior for the saturation value of the COP with a varying damping coefficient. For the inverted oscillator, we find a linear growth of the COP with time for all values of the bath-system interaction. However, when the interaction is increased the slope of the linear growth decreases, implying that the unstable nature of the system can be regulated by the bath.

We construct a relativistic model for bulk viscosity and heat conduction in a superfluid. Building on the principles of unified extended irreversible thermodynamics, the model is derived from Carter’s multifluid approach for a theory with 3 four-currents: particles, entropy, and quasiparticles. Dissipation arises directly from the fact that the quasiparticle four-current is an independent degree of freedom that does not necessarily comove with the entropy. For small deviations from local thermodynamic equilibrium, the model provides an extension of the Israel-Stewart theory to superfluid systems. It can, therefore, be made hyperbolic, causal, and stable if the microscopic input is accurate. The nondissipative limit of the model is the relativistic two-fluid model of Carter, Khalatnikov, and Gusakov. The Newtonian limit of the model is an extended-irreversible-thermodynamic extension of Landau’s two-fluid model. The model predicts the existence of four bulk viscosity coefficients and accounts for their microscopic origin, providing their exact formulas in terms of the quasiparticle creation rate. Furthermore, when fast oscillations of small amplitude around the equilibrium are considered, the relaxation-time term in the telegraph-type equations for the bulk viscosities accounts directly for their expected dependence on the frequency.

High-order spatial derivatives are of crucial importance for constructing the low energy effective action of a Lorentz or parity violating theory of quantum gravity. One example is the Hořava-Lifshitz gravity, in which one has to consider at least the sixth-order spatial derivatives in the gravitational action in order to make the theory power-counting renormalizable. In this paper, we consider the Lorentz and parity violating effects on the propagation of GWs due to the fifth and sixth-order spatial derivatives, respectively. For this purpose we calculate the corresponding Lorentz and parity violating waveforms of GWs produced by the coalescence of compact binaries. By using these modified waveforms, we perform the full Bayesian inference with the help of the open source software bilby on the selected GW events of binary black hole (BBH) and binary neutron stars (BNS) merges in the LIGO-Virgo catalogs GWTC-1 and GWTC-2. Overall we do not find any significant evidence of Lorentz and parity violation due to the fifth and sixth-order spatial derivatives and thus place lower bounds on the energy scales $M_{\mathrm{LV}}>2.4\times {10}^{-16}\mathrm{GeV}$ for Lorentz violation and $M_{\mathrm{PV}}>1.0\times {10}^{-14}\mathrm{GeV}$ for parity violation at 90% confidence level. Both constraints represent the first constraints on the fifth- and sixth-order spatial derivative terms respectively in the framework of spatial covariant gravity by using the observational data of GWs.

We study slow-roll inflation and the generation of primordial fluctuations in $F(T)$ gravity’s rainbow. We obtain the second order action for scalar and tensor perturbations and then calculate the primordial power spectrum for them. Thus, after calculating the inflationary observables up to first order in slow-roll approximation, namely the scalar spectral index $n_s$ and the tensor-to scalar ratio $r$, we confront the predictions of the model with the current PLANCK and BICEP/Keck data.

We provide an end-to-end exploration of a distinct modified gravitational theory in Jordan-Brans-Dicke (JBD) gravity, from an analytical and numerical description of the background expansion and linear perturbations, to the nonlinear regime captured with a hybrid suite of $N$-body simulations, to the cosmological constraints from existing probes of the expansion history, the large-scale structure, and the cosmic microwave background (CMB). We have focused on JBD gravity as it both approximates a wider class of Horndeski scalar-tensor theories on cosmological scales and allows us to adequately model the nonlinear corrections to the matter power spectrum. In a combined analysis of the Planck 2018 CMB temperature, polarization, and lensing reconstruction, together with Pantheon supernova distances and the Baryon Oscillation Spectroscopic Survey (BOSS) measurements of baryon acoustic oscillation distances, the Alcock-Paczynski effect, and the growth rate, we constrain the JBD coupling constant to ${\omega }_{\mathrm{BD}}>970$ (95% confidence level; C.L.) in agreement with the General Relativistic expectation given by ${\omega }_{\mathrm{BD}}\to \infty$. In the unrestricted JBD model, where the effective gravitational constant at present, $G_{\text{matter}}/G$, is additionally varied, increased dataset concordance (e.g., within $1\sigma$ agreement in $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_{\mathrm{m}}/0.3})$ enables us to further include the combined (“$3\times 2\mathrm{pt}$”) dataset of cosmic shear, galaxy-galaxy lensing, and overlapping redshift-space galaxy clustering from the Kilo Degree Survey and the 2-degree Field Lensing Survey ($\mathrm{KiDS}\times 2\mathrm{dFLenS}$). In analyzing the weak lensing measurements, the nonlinear corrections due to baryons, massive neutrinos, and modified gravity are simultaneously modeled and propagated in the cosmological analysis for the first time. In the joint analysis of all datasets, we constrain ${\omega }_{\mathrm{BD}}>1540$ (95% C.L.), $G_{\text{matter}}/G=0.997\pm 0.029$, the sum of neutrino masses, $\sum m_{\nu }<0.12\mathrm{eV}$ (95% C.L.), and the baryonic feedback amplitude, $B<2.8$ (95% CL), all in agreement with the standard model expectation. In fixing the sum of neutrino masses, the lower bound on the coupling constant strengthens to ${\omega }_{\mathrm{BD}}>1460$ and ${\omega }_{\mathrm{BD}}>2230$ (both at 95% C.L.) in the restricted and unrestricted JBD models, respectively. We explore the impact of the JBD modeling choices, and show that a more restrictive parametrization of the coupling constant degrades the neutrino mass bound by up to a factor of three. In addition to the improved concordance between $\mathrm{KiDS}\times 2\mathrm{dFLenS}$ and Planck, the tension in the Hubble constant between Planck and the direct measurement of Riess et al. (2019) is reduced to $\sim 3\sigma$; however, we find no substantial model selection preference for JBD gravity relative to $\mathrm{\Lambda }\mathrm{CDM}$. We further show that a positive shift in the effective gravitational constant suppresses the CMB damping tail, which might complicate future inferences of small-scale physics, given its degeneracy with the primordial helium abundance, the effective number of neutrinos, and the running of the spectral index.

The LISA Pathfinder (LPF) mission succeeded outstandingly in demonstrating key technological aspects of future space-borne gravitational-wave detectors, such as the Laser Interferometer Space Antenna (LISA). Specifically, LPF demonstrated with unprecedented sensitivity the measurement of the relative acceleration of two free-falling cubic test masses. Although most disruptive nongravitational forces have been identified and their effects mitigated through a series of calibration processes, some faint transient signals of yet unexplained origin remain in the measurements. If they appear in the LISA data, these perturbations (also called glitches) could skew the characterization of gravitational-wave sources or even be confused with gravitational-wave bursts. For the first time, we provide a comprehensive census of LPF transient events. Our analysis is based on a phenomenological shapelet model allowing us to derive simple statistics about the physical features of the glitch population. We then implement a generator of synthetic glitches designed to be used for subsequent LISA studies, and perform a preliminary evaluation of the effect of the glitches on future LISA data analyses.

The three point correlation function of color charge densities is evaluated explicitly in light -one gauge for a proton on the light cone. This includes both $C$-conjugation even and odd contributions. We account for perturbative corrections to the three-quark light -cone wave function due to the emission of an internal gluon which is not required to be soft. We verify the Ward identity as well as the cancellation of UV divergences in the sum of all diagrams so that the correlator is independent of the renormalization scale. It does, however, exhibit the well-known soft and collinear singularities. The expressions derived here provide the $C$-odd contribution to the initial conditions for high-energy evolution of the dipole scattering amplitude to small $x$. Finally, we also present a numerical model estimate of the impact parameter dependence of quantum color charge three-point correlations in the proton at moderately small $x$.

We consider a multicomponent dark matter model where the dark sector contains a scalar doublet and a complex scalar singlet. We impose a discrete $Z_4$ symmetry to ensure such that the lightest component of the doublet, $\tilde{A}$, and the singlet, $\tilde{S}$, are both stable. Interactions between the dark sectors impact significantly dark matter observables, and they allow, in particular, to significantly relax the direct detection constraints on the model. To determine the parameter space that satisfies relic density and theoretical and collider constraints as well as direct and indirect detection limits, we perform two separate scans. The first includes the full parameter space of the model, while the second is dedicated to scenarios with a compressed inert doublet spectrum. In the first case, we find that the singlet is generally the dominant dark matter component, while in the compressed case the doublet is more likely to be the dominant dark matter component. In both cases, we find that the two dark matter particles can have masses that range from around $m_h/2$ to over the TeV scale. We emphasize the interplay between cosmological astrophysical and collider constraints and show that a large fraction of the parameter space that escapes current constraints is within the sensitivity reach of future detectors such as XENON-nT, Darwin, or the Cherenkov Telescope Array. Important collider signatures are mostly found in the compressed spectrum case with the possibility of probing the model with searches for heavy stable charged particles and disappearing tracks. We also show that semiannihilation processes such as $\tilde{S}\tilde{S}\to \tilde{A}Z$ could give the dominant signature in indirect detection searches.

We study pion-pion scattering in partially-quenched twisted-mass lattice QCD using chiral perturbation theory. The specific partially-quenched setup corresponds to that used in numerical lattice QCD calculations of the $I=0$ scattering length. We study the discretization errors proportional to $a^2$, with $a$ the lattice spacing, and the errors that arise due to the use of Lüscher’s two-particle quantization condition in a theory that is not unitary. We argue that the former can be as large as $\sim 100\%$, but explain how they can be systematically subtracted using a calculation of the $I=2$ scattering amplitude in the same partially-quenched framework. We estimate the error from the violation of unitarity to be $\sim 25\%$, and argue that this error will be difficult to reduce in practice.

Large angle gluon radiations induced by multiple parton scatterings contribute to dijet production in deeply inelastic scattering off a large nucleus at the electron-ion collider. Within the generalized high-twist approach to multiple parton scattering, contributions at the leading order and twist four in perturbative QCD and large Bjorken momentum fraction $x_B$ can be expressed as a convolution of the multiple parton scattering amplitudes and the transverse momentum dependent (TMD) two-parton correlation matrix elements. We study this medium-induced dijet spectrum and its azimuthal angle correlation under the approximation of small longitudinal momentum transfer in the secondary scattering and the factorization of two-parton correlation matrix elements as a product of the quark and gluon TMD parton distribution function (PDF). Contributions to dijet cross section from double scattering are power suppressed and only become sizable for minijets at small transverse momentum. We find that the total dijet correlation for these minijets, which also includes the contribution from single scattering, is sensitive to the transverse momentum broadening in the quark TMD PDF at large $x$ and saturation in the gluon TMD PDF at small $x$ inside the nucleus. The correlation from double scattering is also found to increase with the dijet rapidity gap and have a quadratic nuclear-size dependence because of the Landau-Pomeranchuk-Migdal interference in gluon emission induced by multiple scattering. Experimental measurements of such unique features in the dijet correlation can shed light on the Landau-Pomeranchuk-Migdal interference in strong interaction and gluon saturation in large nuclei.