In this article, we examine the Standard Model extended with a $Y=0$ Higgs triplet and a real singlet. We consider the Higgs triplet to be odd under the $Z_2$ symmetry, and hence the lightest stable particle from the inert triplet becomes the dark matter candidate, whereas the real singlet is considered to be even under the $Z_2$ symmetry. A dimension-5 effective term is introduced with the help of a real singlet, which breaks the $CP$ symmetry and gives an additional source of $CP$-violation in the fermion sector. The phase transition proceeds in two steps, with the symmetry breaking in the singlet direction occurring first and later leading to the usual electroweak symmetry breaking minima, while electroweak baryogenesis is associated with the second step. The parameters chosen for the electroweak phase transition are found to be consistent with the Planck-scale stability and the perturbativity using two-loop $\beta$-functions. The DM mass bound for inert triplet, i.e., 1.2 TeV (below which it is under abundance), also comes out to be consistent with the strongly first-order phase transition, which was not possible solely with inert triplet. The upper bound on the triplet mass comes out to be $\le 3.8\mathrm{TeV}$, which satisfies the strongly first-order phase transition. This particular benchmark point also satisfies the correct baryon asymmetry of the Universe $(6.13\times {10}^{-11})$, and the gravitational wave spectrum also lies within the detectable frequency range of LISA $(6.978\times {10}^{-4}-1.690\times {10}^{-2})\mathrm{Hz}$ and BBO $(2.80\times {10}^{-3}-1.096)\mathrm{Hz}$ experiments.

We present a complete and nonredundant basis of effective operators for the Standard Model effective field theory up to mass dimension 12 with three generations of fermions. We also include operators coupling to gravity via the Weyl tensor. The results are obtained by implementing the algorithm of Li et al. and are provided in the form of Supplemental Material.

The properties of fully heavy arrangements including a number of quarks between 5 and 12 were calculated within the framework of a constituent quark model by using a diffusion Monte Carlo technique. We considered only clusters in which all the quarks had the same mass and whose number of particles and antiparticles were adequate to produce color singlets. All the multiquarks were in their lowest possible values of $L^2$ and $S^2$ operators. Thus, we considered only color-spin wave functions that were antisymmetric with respect to the interchange of any two quarks of the same type. We found that in both all-$c$ and all-$b$ multiquarks, the mass per particle levels off for arrangements with the number of quarks larger than or equal to six. The analysis of their structure implies that the fully heavy multiquarks are compact structures.

In this work, we study the lepton number violating $B_c$ meson decays via one intermediate on-shell heavy neutrino $N$. The specific studied process is $B_c^{+}\to {\mu }^{+}N\to {\mu }^{+}{\mu }^{+}{\tau }^{-}\nu$ which could allow distinguishing the nature of the heavy neutrino nature (Dirac or Majorana) by studying the tau lepton energy spectrum in the LHCb experiment. The result suggests that this signature could be observed in the collected data during the HL-LHCb lifetime.

High frequency gravitational waves can be detected by observing the frequency modulation they impart on photons. We discuss fundamental limitations to this method related to the fact that it is impossible to construct a perfectly rigid detector. We then propose several novel methods to search for $\mathcal{O}(\mathrm{MHz}-\mathrm{GHz})$ gravitational waves based on the frequency modulation induced in the spectrum of an intense laser beam, by applying optical frequency demodulation techniques, or by using optical atomic clock technology. We find promising sensitivities across a broad frequency range.

We provide a possible way of avoiding the hair-loss problem by studying gauge fluctuations on classical Schwarzschild black hole background. The hair-loss problem arises due to the small fidelity of reconstructing the interior operator at the end stage of the evaporation, which is general in most schemes trying to decouple the early and late radiation to avoid firewall. To circumvent the problem, we put the black hole in a cavity as a toy model and study the entropy behavior of the system with different temperatures. By analyzing gauge fluctuations with nontrivial boundary conditions, we find that the entropy of the black hole system increases at the end stage, rather than directly dropping to zero. Besides the end stage, the entropy is the same as Page’s original argument. The hair-loss problem can be avoided by the proposed model and we can gain important insights into the end stage of the evaporation and quantum effects of gravity.

We obtain the holographic entanglement negativity for bipartite mixed states at a finite temperature in baths described by conformal field theories dual to configurations involving two communicating black holes in a braneworld geometry. In this context, we analyze the mixed state entanglement structure characterized by the information transfer between the black holes. The model corresponds to a configuration of two dimensional eternal Jackiw-Teitelboim (JT) black holes in a braneworld geometry involving two Planck branes coupled through shared bath systems described by ${\mathrm{CFT}}_2\mathrm{s}$. Our results reproduce analogue of the Page curves for the entanglement negativity obtained earlier in the context of random matrix theory and from geometric evaporation in JT black hole configurations.

Motivated by the fermionic Berry’s phase in momentum space, we study a local Abelian phase in momentum space coupled to electromagnetism, for complex scalars in the phase-space worldline formalism. The interaction of both Abelian fields is shown to give rise to a momentum gauge dependent emergent spacetime. As a concrete example, we further study classical solutions of the Berry-inspired gauge field that lead to an emergent Newtonian gravity with gravitational potential predicted by coupled Coulomb fields both in configuration and momentum spaces. Noncommutative aspects of the theory are also provided.

Stochastic gravitational-wave backgrounds (SGWBs) derive from the superposition of numerous individually unresolved gravitational-wave (GW) signals. Detecting SGWBs provides us with invaluable information about astrophysics, cosmology, and fundamental physics. In this paper, we study SGWBs from binary black-hole (BBH) and binary neutron-star (BNS) coalescences in a network of next-generation ground-based GW observatories (Cosmic Explorer and Einstein Telescope) and determine how well they can be measured; this then limits how well we can observe other subdominant astrophysical and cosmological SGWBs. We simulate all-Universe populations of BBHs and BNSs and calculate the corresponding SGWBs, which consist of a superposition of (i) undetected signals and (ii) the residual background from imperfect removal of resolved sources. The sum of the two components sets the sensitivity for observing other SGWBs. Our results show that, even with next-generation observatories, the residual background is large and limits the sensitivity to other SGWBs. The main contributions to the residual background arise from uncertainties in inferring the coalescence phase and luminosity distance of the detected signals. Alternative approaches to signal subtraction would need to be explored to minimize the BBH and BNS foreground in order to observe SGWBs from other subdominant astrophysical and cosmological sources.

We study gravitational radiation for a positive value of the cosmological constant $\mathrm{\Lambda }$. We rely on two battle-tested procedures: (i) We start from the same null coordinate system used by Bondi and Sachs for $\mathrm{\Lambda }=0$, but, introduce boundary conditions adapted to allow radiation when $\mathrm{\Lambda }>0$; and (ii) We determine the asymptotic symmetries by studying, à la Regge-Teitelboim, the surface integrals generated in the action by these boundary conditions. A crucial difference with the $\mathrm{\Lambda }=0$ case is that the wave field does not vanish at large distances, but is of the same order as de Sitter space. This novel property causes no difficulty; on the contrary, it makes quantities finite at every step, without any regularization. A direct consequence is that the asymptotic symmetry algebra consists only of time translations and space rotations. Thus, it is not only finite dimensional, but smaller than de Sitter algebra. We exhibit formulas for the energy and angular momentum and their fluxes. In the limit of $\mathrm{\Lambda }$ tending to zero, these formulas go over continuously into those of Bondi, but the symmetry jumps to that of Bondi, Metzner, and Sachs. The expressions are applied to exact solutions, with and without radiation present, and also to the linearized theory.

We study the effects of geontropic vacuum fluctuations in quantum gravity on next-generation terrestrial gravitational wave detectors. If the Verlinde-Zurek (VZ) effect proposed in Verlinde and Zurek [Phys. Lett. B 822, 136663 (2021).], as modeled in Zurek [Phys. Lett. B 826, 136910 (2022); Li et al. Phys. Rev. D 107, 024002 (2023)], appears in the upcoming GQuEST experiment, we show that it will be a large background for astrophysical gravitational wave searches in observatories like Cosmic Explorer and the Einstein Telescope.

We study the cosmological effects of a Galileon term in scalar-tensor theories of gravity. The subset of scalar-tensor theories considered are characterized by a nonminimal coupling $F(\sigma )R$, a kinetic term with arbitrary sign $Z(\partial \sigma {)}^2$ with $Z=\pm 1$, a potential $V(\sigma )$, and a Galileon term $G_3(\sigma ,(\partial \sigma {)}^2)\square \sigma$. In addition to the modified dynamics, the Galileon term provides a screening mechanism to potentially reconcile the models with general relativity predictions inside a Vainshtein radius. Thanks to the Galileon term, the stability conditions, namely, ghost and Laplacian instabilities, in the branch with a negative kinetic term ($Z=-1$) are fulfilled for a large volume of the parameter space. Solving numerically the background evolution and linear perturbations, we derive the constraints on the cosmological parameters in the presence of a Galileon term for different combination of the cosmic microwave background data from Planck, baryon acoustic oscillations measurements from BOSS, and supernovae from the Pantheon compilation. We find that the Galileon term alters the dynamics of all the studied cases. For a standard kinetic term ($Z=1$), we find that Planck data and a compilation of baryon acoustic oscillations data constrain the Galileon term to small values that allow screening very inefficiently. For a negative kinetic term ($Z=-1$), a Galileon term and a nonzero potential lead to an efficient screening in a physically viable regime of the theory, with a value for the Hubble constant today which alleviates the tension between its cosmic microwave background and local determinations. For a vanishing potential, the case with $Z=-1$ and the Galileon term driving the late acceleration of the Universe is ruled out by Planck data.

We examine solar neutrinos in dark matter detectors including the effects of flavor-dependent radiative corrections to the $\mathrm{CE}\nu \mathrm{NS}$ cross section. Working within a full three-flavor framework, and including matter effects within the Sun and Earth, detectors with thresholds $\lesssim 1\mathrm{keV}$ and exposures of $\sim 100$ ton-year could identify contributions to the cross section beyond tree level. The differences between the cross sections for the flavors, combined with the difference in fluxes, would provide a new and unique method to study the muon and tau components of the solar neutrino flux. Flavor-dependent corrections induce a small day-night asymmetry of $<|3\times {10}^{-4}|$ in the event rate, which if ultimately accessible would provide a novel probe of flavor oscillations.

In this work, we study a model that describes the $(2+1)\mathrm{D}$ Yukawa interaction for static particles confined to the plane. In order to do so, we perform a dimensional reduction of a $(3+1)\mathrm{D}$ massive vector field whose mass term introduces a natural scale for a correlation length within the system. We derive the projected model similarly to the so-called pseudo (or reduced) quantum electrodynamics that has been used in several applications. One-loop radiative corrections to the electron and to the massive vector-field mass are computed, as well as the vertex corrections; this brings forth the quantum correction to the electron $g$ factor, demonstrating that it smoothly goes to zero when the mass of the vector field is significantly larger than the electron mass and generalizing the results obtained for graphene within pseudo-QED to a system with a correlation length. Such a limit is expected to emerge due to many-body interactions in two-dimensional materials. Furthermore, the model is likely to be relevant in the relativistic limit, when electrons move with a high velocity.

We study nonequilibrium dynamics of SU(2) lattice gauge theory in Minkowski space-time in a classical-statistical regime, where characteristic gluon occupancies are much larger than unity. In this strongly correlated system far from equilibrium, the correlations of energy and topological densities show self-similar behavior related to a turbulent cascade toward higher momentum scales. We employ persistent homology to infer topological features of the gluonic plasma via a hierarchy of simplicial and cubical complexes. All topological observables under investigation are also manifestly gauge invariant and are shown to exhibit self-similar evolution, which relates the spatial and temporal properties of the plasma in terms of universal scaling exponents and functions. The findings may help one to understand the early stages of heavy-ion collisions in the limit of high energies, and our methods can also facilitate the topological analysis of other complex systems such as those encountered in experiments with ultracold quantum gases.

Assuming that the $P_{\psi }^N(4312{)}^{+}$ is a $I(J^P)=\frac{1}{2}({\frac{3}{2}}^{-})$ compact pentaquark, we study the mass spectrum of its $S$-wave hidden-charm partner states in a color-magnetic interaction model. Combining the information from their decays obtained in a simple rearrangement scheme, one finds that the quantum numbers of $P_{\psi }^N(4457{)}^{+}$, $P_{\psi }^N(4440{)}^{+}$, and $P_{\psi }^N(4337{)}^{+}$ can be assigned to be $I(J^P)=\frac{1}{2}({\frac{3}{2}}^{-})$, $\frac{1}{2}({\frac{1}{2}}^{-})$, and $\frac{1}{2}({\frac{1}{2}}^{-})$, respectively, while both $P_{\psi s}^{\mathrm{\Lambda }}(4338{)}^0$ and $P_{\psi s}^{\mathrm{\Lambda }}(4459{)}^0$ can be interpreted as $I(J^P)=0({\frac{1}{2}}^{-})$ $udsc\overline{c}$ compact states. Based on the numerical results, we also find narrow pentaquarks in $ssnc\overline{c}$ ($n=u$, $d$) and $sssc\overline{c}$ systems. The decay properties of the studied pentaquarks and the searching channels for them can be tested in future experiments.

We conduct a comprehensive analysis of the potential for discovering lepton flavor violation (LFV) phenomena associated with the $Z$ and Higgs bosons at the LHeC and FCC-he. Our thorough investigation highlights the exceptional suitability of electron-proton colliders for probing these rare new physics signals, due to their distinct advantages, such as negligible pileups, minimal QCD backgrounds, electron-beam polarization $P_e$, and the ability to distinguish charged-current from neutral-current processes. In our analysis of LFV of the $Z$ boson, we employ an innovative indirect probe, utilizing the $t$-channel mediation of the $Z$ boson in the process $p{e}^{-}\to j{\tau }^{-}$. For LFV in the Higgs sector, we examine direct observations of the on-shell decays of $H\to e^{+}{\tau }^{-}$ and $H\to {\mu }^{\pm }{\tau }^{\mp }$ through the charged-current production of $H$. Focusing on $H\to e^{+}{\tau }^{-}$ is highly efficient due to the absence of positron-related backgrounds in the charged-current modes at electron-proton colliders. Through a dedicated signal-to-background analysis using the boosted decision tree algorithm, we show that the LHeC with a total integrated luminosity of $1{\mathrm{ab}}^{-1}$ can establish significantly lower $2\sigma$ bounds than the HL-LHC with $3{\mathrm{ab}}^{-1}$. Specifically, we find $\mathrm{Br}(Z\to e\tau )<2.2\times {10}^{-7}$, $\mathrm{Br}(H\to e\tau )<1.7\times {10}^{-4}$, and $\mathrm{Br}(H\to \mu \tau )<1.0\times {10}^{-4}$ when we apply the optimal cut on the boosted decision tree output. Furthermore, our study reveals the exceptional precision of the FCC-he in measuring the LFV signatures of the $Z$ and Higgs bosons, indicating a promising potential for future discoveries in this fascinating field.

We revisit the phenomenology of neutrinoless double beta ($0\nu \beta \beta$) decay mediated by noninterfering exchange of light and heavy Majorana neutrinos, in the context of current and prospective ton-scale experimental searches, as well as of recent calculations of nuclear matrix elements (NME) in different nuclear models. We derive joint upper bounds on the light and heavy contributions to $0\nu \beta \beta$ decay, for different sets of NME, through separate and combined data coming from the following experiments (and isotopes): KamLAND-Zen and EXO (Xe), GERDA and MAJORANA (Ge), and CUORE (Te). We further consider three proposed projects that could provide, within current bounds, possible $0\nu \beta \beta$ decay signals at $>3\sigma$ level with an exposure of 10 ton years: nEXO (Xe), LEGEND (Ge), and CUPID (Mo). Separate and combined (Xe, Ge, Mo) signals are studied for different representative cases and NME sets, and the conditions leading to (non)degenerate light and heavy neutrino mechanisms are discussed. In particular, the role of heavy-to-light NME ratios in different isotopes is highlighted through appropriate graphical representations. By using different sets of “true” and “test” NME as a proxy for nuclear uncertainties, it is shown that the relative contributions of light and heavy neutrino exchange to $0\nu \beta \beta$ signals may be significantly biased in some cases. Implications for theoretical models connecting light and heavy Majorana neutrino masses are also briefly illustrated. These results provide further motivations to improve NME calculations, so as to better exploit the physics potential of future multi-isotope $0\nu \beta \beta$ searches at the ton scale.

We propose to search for a new type of gravitational wave signature relevant for particle physics models with symmetries broken at vastly different energy scales. The spectrum contains a characteristic double-peak structure consisting of a sharp peak from domain walls and a smooth bump from a first order phase transition in the early universe. We demonstrate how such a gravitational wave signal arises in a new theory unifying baryon number and color into an SU(4) gauge group broken at the multi-TeV scale, and with the lepton number promoted to an SU(2) gauge symmetry broken at the multi-EeV scale. The model contains two types of dark matter particles, explains the observed domination of matter over antimatter in the Universe, and accommodates nonzero neutrino masses. We discuss how future gravitational wave experiments, such as LISA, Big Bang Observer, DECIGO, Einstein Telescope, and Cosmic Explorer, can be utilized to look for this novel signature.