We show how Einstein-Cartan gravity can accommodate both global scale and local scale (Weyl) invariance. To this end, we construct a wide class of models with nonpropagating torsion and a nonminimally coupled scalar field. In phenomenological applications the scalar field is associated with the Higgs boson. For global scale invariance, an additional field—dilaton—is needed to make the theory phenomenologically viable. In the case of the Weyl symmetry, the dilaton is spurious and the theory reduces to a subclass of one-field models. In both scenarios of scale invariance, we derive an equivalent metric theory and discuss possible implications for phenomenology.

We present an analytic study of the density fluctuation of a Newtonian self-gravity fluid in the expanding universe with ${\mathrm{\Omega }}_{\mathrm{\Lambda }}+{\mathrm{\Omega }}_m=1$, which extends our previous work in the static case. By the use of field theory techniques, we obtain the nonlinear, hyperbolic equation of two-point correlation function $\xi$ of perturbation. Under the Zel’dolvich approximation the equation becomes an integro-differential equation and contains also the three-point and four-point correlation functions. By adopting the Groth-Peebles and Fry-Peebles ansatz, the equation becomes closed, and contains a pressure term and a delta source term which were neglected in Davis and Peebles’ milestone work. The equation has three parameters of fluid; the particle mass $m$ in the source, the overdensity $\gamma$, and the sound speed $c_s$. We solve only the linear equation in linear approximation and apply it to the system of galaxies. We assume two models of $c_s$, and take an initial power spectrum at a redshift $z=7$, which inherits the relevant imprint from the spectrum of baryon acoustic oscillations at the decoupling. The solution $\xi (\mathbf{r},z)$ is growing during expansion, and contains 100 Mpc periodic bumps at large scales, and a main mountain (a global maximum with $\xi \propto r^{-1}$) at small scales $r\lesssim 50\mathrm{Mpc}$. The profile of $\xi$ agrees with the observed ones from galaxy and quasar surveys. The bump separation is given by the Jeans length ${\lambda }_J$, and is also modified by $\gamma$ and $c_s$. Using a decomposition we find that the main mountain is largely generated by the inhomogeneous solution with the source, and the periodic bumps come from the homogeneous solution with the initial spectrum. ${\lambda }_J$ is identified as the correlation scale of the system of galaxies, distinguished from the clustering scale determined by $m$. The corresponding power spectrum has a main peak located around $k\sim \frac{2\pi }{{\lambda }_J}$ associated with the periodic bumps of $\xi$, and also contains multiwiggles at high $k>k_J$ which are developing during evolution even if the initial spectrum has no wiggles. Since the outcome is affected by the initial condition and the parameters as well, it is hard to infer the imprint of baryon acoustic oscillations accurately. The difficulties with the sound horizon as a distance ruler are pointed out.

Inspired by the recent conjecture originated from graduated dark energy that the Universe has recently transitioned from anti–de Sitter vacua to de Sitter vacua, we extend the standard $\mathrm{\Lambda }\mathrm{CDM}$ model by a cosmological constant (${\mathrm{\Lambda }}_s$) that switches sign at a certain redshift $z_{†}$, and we call this model ${\mathrm{\Lambda }}_s\mathrm{CDM}$. We discuss the construction and theoretical features of this model in detail and find out that, when the consistency of the ${\mathrm{\Lambda }}_s\mathrm{CDM}$ model with the cosmic microwave background (CMB) data is ensured, (i) $z_{†}\gtrsim 1.1$ is implied by the condition that the Universe monotonically expands, (ii) $H_0$ and $M_B$ (type Ia supernovae absolute magnitude) values are inversely correlated with $z_{†}$ and reach $H_0\approx 74.5\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ and $M_B\approx -19.2\mathrm{mag}$ for $z_{†}=1.5$, in agreement with the SH0ES measurements, and (iii) $H(z)$ presents an excellent fit to the Ly-$\alpha$ measurements provided that $z_{†}\lesssim 2.34$. We further investigate the model constraints by using the full Planck CMB data set, with and without baryon acoustic oscillation (BAO) data. We find that the CMB data alone does not constrain $z_{†}$, but the $\mathrm{CMB}+\mathrm{BAO}$ data set favors the sign switch of ${\mathrm{\Lambda }}_s$, providing the constraint $z_{†}=2.44\pm 0.29$ (68% C.L.). Our analysis reveals that the lower and upper limits of $z_{†}$ are controlled by the Galaxy and Ly-$\alpha$ BAO measurements, respectively, and the larger $z_{†}$ values imposed by the Galaxy BAO data prevent the model from achieving the highest local $H_0$ measurements. In general, the ${\mathrm{\Lambda }}_s\mathrm{CDM}$ model (i) relaxes the $H_0$ tension while being fully consistent with the tip of the red giant branch measurements, (ii) relaxes the $M_B$ tension, (iii) removes the discrepancy with the Ly-$\alpha$ measurements, (iv) relaxes the $S_8$ tension, and (v) finds a better agreement with the big bang nucleosynthesis constraints on the physical baryon density. We find no strong statistical evidence to discriminate between the ${\mathrm{\Lambda }}_s\mathrm{CDM}$ and $\mathrm{\Lambda }\mathrm{CDM}$ models. However, interesting and promising features of the ${\mathrm{\Lambda }}_s\mathrm{CDM}$ model, which we describe in our study, provide an advantage over $\mathrm{\Lambda }\mathrm{CDM}$.

Do neutrinos have sizable self-interactions? They might. Laboratory constraints are weak, so strong effects are possible in astrophysical environments and the early Universe. Observations with neutrino telescopes can provide an independent probe of neutrino self (“secret”) interactions, as the sources are distant and the cosmic neutrino background intervenes. We define a roadmap for making decisive progress on testing secret neutrino interactions governed by a light mediator. This progress will be enabled by IceCube-Gen2 observations of high-energy astrophysical neutrinos. Critical to this is our comprehensive treatment of the theory, taking into account previously neglected or overly approximated effects, as well as including realistic detection physics. We show that IceCube-Gen2 can realize the full potential of neutrino astronomy for testing neutrino self-interactions, being sensitive to cosmologically relevant interaction models. To facilitate forthcoming studies, we release nusiprop, a code that can also be used to study neutrino self-interactions from a variety of sources.

We derive a new model for neutrino-plasma interactions in an expanding universe that incorporates the collective effects of the neutrinos on the plasma constituents. We start from the kinetic description of a multispecies plasma in the flat Friedmann-Robertson-Walker metric, where the particles are coupled to neutrinos through the charged- and neutral-current forms of the weak interaction. We then derive the fluid equations and specialize our model to (a) the lepton epoch, where we consider a pair electron-positron plasma interacting with electron (anti)neutrinos, and (b) after the electron-positron annihilation, where we model an electron-proton plasma and take the limit of slow ions and inertialess electrons to obtain a set of neutrino-electron magnetohydrodynamics equations. In both models, the dynamics of the plasma is affected by the neutrino motion through a ponderomotive force and, as a result, new terms appear in the induction equation that can act as a source for magnetic field generation in the early Universe. A brief discussion on the possible applications of our model is proposed.

A fraction of light scalar dark matter, especially axions, may organize into Bose-Einstein condensates, gravitationally bound clumps, “boson stars”, and be present in large number in galactic halos today. We compute the expected number of gravitational microlensing events of clumps composed of the ordinary QCD axion and axionlike particles and derive microlensing constraints from the EROS-2 survey and the Subaru Hyper Suprime-Cam observation. We perform a detailed lensing calculation, including the finite lens and source size effects in our analysis. We constrain the axion mass in terms of the fraction of dark matter collapsed into clumps, the individual clump densities, and the axion self-coupling. We also consider and constrain clumps composed of a generic scalar dark matter candidate with repulsive self-interactions. Our analysis opens up a new window for the potential discovery of dark matter.

With a laser interferometric gravitational-wave detector in separate free flying spacecraft, the only way to achieve detection is to mitigate the dominant noise arising from the frequency fluctuations of the lasers via postprocessing. The noise can be effectively filtered out on the ground through a specific technique called time-delay interferometry (TDI), which relies on the measurements of time delays between spacecraft and careful modeling of how laser noise enters the interferometric data. Recently, this technique has been recast into a matrix-based formalism by several authors, offering a different perspective on TDI, particularly by relating it to principal component analysis (PCA). In this work, we demonstrate that we can cancel laser frequency noise by directly applying PCA to a set of shifted data samples, without any prior knowledge of the relationship between single-link measurements and noise, nor time delays. We show that this fully data-driven algorithm achieves a gravitational-wave sensitivity similar to classic TDI.

In this work, we propose that there exists a moving triangle singularity in the $\psi (2S)\to {\pi }^{+}{\pi }^{-}{K}^{+}{K}^{-}$ process, whose position can vary from 1.158 to 1.181 GeV in the invariant mass spectrum of $K^{+}{K}^{-}$. After a precise analysis on this process, it turns out that after doing some cuts on $m_{{\pi }^{+}{\pi }^{-}}$, experiments do have the opportunity to observe this triangle singularity. In addition, when changing the cuts on $m_{{\pi }^{+}{\pi }^{-}}$, the movement of the predicted triangle singularity can also be observed. Thus, we suggest future experiments, especially Super Tau-Charm Facility (STCF), to do an analysis on the $\psi (2S)\to {\pi }^{+}{\pi }^{-}{K}^{+}{K}^{-}$ process to verify our prediction.

We study the decay properties of a $D(2900)$ state, with spin parity $0^{-}$, whose existence was proposed in an earlier study of the $DK\overline{K}$ and coupled-channel system. It was found in the former work that a $D$ meson appears with a mass of about 2900 MeV from the three-body dynamics while the charmless subsystem of the pseudoscalar mesons forms the $f_0(980)$ resonance. Motivated by the recent experimental investigations of $D$ mesons around 3000 MeV, we now study the two-body decays of $D(2900)$. We find that the nature of the said state sets the main decay channels to be $D^{*}\pi$, $D_s^{*}\overline{K}$ and $D_{s0}^{*}(2317)\overline{K}$. It turns out that decay width to the last one is the largest, making the $D_{s0}^{*}(2317)\overline{K}$ system to be the most favorable one to look for a signal of $D(2900)$. We compare the decay properties of our state with those of the $D$-meson states, proposed within quark models, near 3000 MeV. We hope that our findings and discussions can be useful for the future experimental investigations of charm mesons around 3000 MeV.

We investigate the prospects of the search for a nonzero $\tau$ EDM form factor $d_{\tau }(s)$ in $\tau$-pair production by $e^{+}{e}^{-}$ collisions at BEPC-II collider energies. We compute the expectation values and covariances of simple and optimal $CP$-odd observables for $\tau$-pair production at $\sqrt{s}=4.18$ and 4.95 GeV with subsequent decays of ${\tau }^{\pm }$ into major leptonic or semihadronic modes. For the $\tau$ decays to two pions and three charged pions, we take the full kinematic information of the hadronic system into account. Applying cuts and using realistic assumptions on the eventually attainable integrated luminosities at these energies, $\mathcal{L}(4.18)=3\times {10}^4{\mathrm{pb}}^{-1}$ and $\mathcal{L}(4.95)={10}^4{\mathrm{pb}}^{-1}$, respectively, we find the following. By taking into account purely semihadronic and semihadronic-leptonic ${\tau }^{+}{\tau }^{-}$ decays one can achieve with optimal $CP$-odd observables the 1 s.d. sensitivities $\delta \mathrm{Re}{d}_{\tau }=4.5\times {10}^{-18}e\mathrm{cm}$ $(5.3\times {10}^{-18}e\mathrm{cm})$ and $\delta \mathrm{Im}{d}_{\tau }=2.2\times {10}^{-18}e\mathrm{cm}$ $(2.7\times {10}^{-18}e\mathrm{cm})$ at $\sqrt{s}=4.18\mathrm{GeV}$ (4.95 GeV).

We study the differential cross section of the single inclusive $e^{+}{e}^{-}$ annihilation to the hadrons via $\gamma$-production, in the different $k_t$-factorization frameworks. In order to take into account the transverse momenta of the incoming partons, for the first time, we apply the Kimber et al. (KMR) method to calculate the unintegrated parton fragmentation functions (UFFs) from the ordinary integrated one, i.e., the parton fragmentation functions (FFs), which satisfy the similar Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations, such as those of parton distribution functions (PDFs). Also, by utilizing the different angular ordering constraints the results corresponding to the Martin et al. (MRW) in the leading order (LO) and the next-to-leading-order (NLO) are obtained. The LO sets of DSS library for the input FFs is used. The numerical results are compared with the experimental data in the different energies which are reported by the different collaborations, such as TASSO, AMY, MARK II, CELLO, DELPHI, SLD, ALEPH and Belle with the other $\mathrm{QCD}+\mathrm{fragmentation}$ models such as pythia6.4 and 8.2 parton showers. The behaviors of the normalized differential cross sections and the multiplicity versus the “transverse momentum” ($p_{\perp }$) are discussed. The final results demonstrate that the KMR and MRW UFFs give a good description of data and there is not much significant difference between the above three schemes. On the other hand, our results become closer to the data for the lower values of $p_{\perp }$ and the higher values of center of mass energies.

Inspired by the observation of the doubly charmed state $T_{cc}$ and following theoretical studies on its spectroscopic parameters, we investigate its magnetic dipole moment, assigning it the quantum numbers $J^P=1^{+}$, and both the compact diquark-antidiquark and molecular structures in the framework of the light cone QCD. We also calculate the magnetic dipole moment of the theoretically predicted singly charmed state, $Z_V^{++}$, with two units of electric charge and the quantum numbers $J^P=1^{-}$ in diquark-antidiquark picture. The numerical results are obtained as ${\mu }_{T_{cc}^{+}-Di}={0.66}_{-0.23}^{+0.34}{\mu }_N$, ${\mu }_{T_{cc}^{+}-\mathrm{Mol}}={0.43}_{-0.22}^{+0.23}{\mu }_N$ and ${\mu }_{Z_V^{++}}={3.35}_{-0.73}^{+0.89}{\mu }_N$. These results may be checked via other phenomenological approaches. The obtained results may be useful in exact determinations of the natures of these states.

In view of the great contribution of neutrino-electron scattering to the deep understanding of electroweak interactions, we focus in this paper on the study of elastic scattering of a muon neutrino by an electron $(e^{-}{\nu }_{\mu }\to e^{-}{\nu }_{\mu })$ in the presence of a circularly polarized electromagnetic field. We perform our theoretical calculation within the framework of Fermi theory using the exact wave functions of charged particles in an electromagnetic field. The expression of the differential cross section (DCS) for this process is obtained analytically in the absence and presence of the laser field. The effect of the field strength and frequency on the exchange of photons as well as on the DCS is presented and analyzed. Massive neutrino effects are also included and discussed. This study, added to the previous ones, will significantly enrich our knowledge in fundamental physics.

Theories with compact extra dimensions are sometimes unstable to decay into a bubble of nothing—an instability resulting in the destruction of spacetime. We investigate the existence of these bubbles in theories where the moduli fields that set the size of the extra dimensions are stabilized at a positive vacuum energy—a necessary ingredient of any theory that aspires to describe the real world. Using bottom-up methods, and focusing on a five-dimensional toy model, we show that four-dimensional de Sitter vacua admit bubbles of nothing for a wide class of stabilizing potentials. We show that, unlike ordinary Coleman-De Luccia tunneling, the corresponding decay rate remains non-zero in the limit of vanishing vacuum energy. Potential implications include a lower bound on the size of compactified dimensions.

We find that the Kerr-(Newman)-${\mathrm{AdS}}_4$ black hole will be shadowless if its rotation parameter is larger than a critical value and shadowless-ness may be related to the appearance of the null hypersurface caustics (NHC) both inside the Cauchy horizon and outside the event horizon for the black hole with the rotation parameter beyond the critical value. Our studies also further confirm that whether an ultraspinning black hole is superentropic or not is unrelated to the existence of the NHC outside the event horizon.

We point out little discussed phenomenon in elementary quantum mechanics. In one-dimensional potential scattering problems, the scattering amplitudes are not uniquely determined at special points in parameter space. We examine a few explicit examples. We also discuss the relation with the pole-skipping phenomena recently found in holographic duality. In the holographic pole skipping, the retarded Green’s functions are not uniquely determined at imaginary Matsubara frequencies. It turns out that this universality comes from the fact that the corresponding potential scattering problem has the angular momentum potential.

In this paper, we show the relation between $sp(4,\mathbb{R})$, the Lie algebra of the symplectic group, and the elements of $Sp(4,\mathbb{R})$. We use this result to obtain some special cases of symplectic matrices relevant to the study of squeezed states. In this regard, we provide some applications in quantum mechanics and analyze the squeezed polymer states obtained from the polymer representation of the symplectic group. Remarkably, the polymer’s dispersions are the same as those obtained for the squeezed states in the usual representation.

In this work, we have analytically devised novel vortex solutions in a rotating holographic superfluid. To achieve this result, we have considered a static disk at the anti–de Sitter ($AdS$) boundary and let the superfluid rotate relative to it. This idea has been numerically exploited in Chuan-Yin Xia et al., [Phys. Rev. D 100, 061901(R) (2019)], where the formation of vortices in such a setting was reported. We have found that these vortex solutions are eigenfunctions of angular momentum. We have also shown that vortices with higher winding numbers are associated with higher quantized rotation of the superfluid. We have, then, analyzed the equation of motion along the bulk AdS direction using the Stürm-Liouville eigenvalue approach. A surprising outcome of our study is that the chemical potential must be purely imaginary. We have then observed that the winding number of the vortices decreases with the increase in the imaginary chemical potential. We conclude from this that an imaginary chemical potential leads to less dissipation in such holographic superfluids.

It was recently shown, that in a class of tensor-multiscalar theories of gravity with a nontrivial target space metric, there exist scalarized neutron star solutions. An important property of these compact objects is that the scalar charge is zero and therefore, the binary pulsar experiments can not impose constraints based on the absence of scalar dipole radiation. Moreover, the structure of the solutions is very complicated. For a fixed central energy density up to three neutron star solutions can exist—one general relativistic and two scalarized—which is quite different from the scalarization in other alternative theories of gravity. In the present paper we address the stability of these solutions using two independent approaches—solving the linearized radial perturbation equations and performing nonlinear simulations in spherical symmetry. The results show that the change of stability occurs at the maximum mass models and all solutions before that point are stable. This leads to the interesting consequence that there exists a stable part of the scalarized branch close to the bifurcation point where the mass of the star increases with the decrease of the central energy density.