We determine the distribution of cosmic string loops directly from simulations, rather than determining the loop production function and inferring the loop distribution from that. For a wide range of loop lengths, the results agree well with a power law exponent $-2.5$ in the radiation era and $-2$ in the matter era, the universal result for any loop production function that does not diverge at small scales. Our results extend those of Ringeval et al. [Cosmological evolution of cosmic string loops, J. Cosmol. Astropart. Phys. 02 (2007) 023.]: we are able to run for 15 times longer in conformal time and simulate a volume 300–2400 times larger. At the times they reached, our simulation is in general agreement with the more negative exponents they found, $-2.6$ and $-2.4$. However, our simulations show that this was a transient regime; at later times, the exponents decline to the values above. This provides further evidence against models with a rapid divergence of the loop density at small scales, such as “model 3” used to analyze LIGO data and predict LISA sensitivity.

The $\rho$ meson gravitational form factors are studied based on a light-front constituent quark model which has been successfully employed to calculate its generalized parton distributions and some low-energy observables. The distributions of energy, spin, pressures, and shear forces inside the $\rho$ meson are explicitly given.

If the mass of dark matter is generated from a cosmological phase transition involving the nucleation of bubbles, the corresponding bubble walls can filter out dark matter particles during the phase transition. Only particles with sufficient momentum to overcome their mass inside the bubbles can pass through the walls. As a result, the dark matter number density after the phase transition has a suppression factor $\exp (-M_{\chi }/2\tilde{\gamma }T)$, where $M_{\chi }$ is the dark matter mass, and $\tilde{\gamma }$ and $T$ are the Lorentz factor and temperature of the incoming fluid in the bubble wall rest frame, respectively. Under certain assumptions, we show that the filtering-out process can naturally provide a large suppression consistent with the observed dark matter density for a wide range of dark matter masses up to the Planck scale. Since the first-order phase transition is the decisive ingredient in our mechanism, a new connection is made between heavy dark matter scenarios and gravitational wave observations.

We explore the interplay between the $h(125)\to \tau \mu$ search at the LHC and $\tau \to \mu \gamma$ at the upcoming Belle II experiment, in the context of the general two Higgs doublet model with extra Yukawa couplings such as ${\rho }_{\tau \mu }$. The search for $h\to \tau \mu$ constrains ${\rho }_{\tau \mu }\cos \gamma$, where $\cos \gamma$ is the $h–H$ mixing angle of $h$ with the exotic $CP$-even scalar $H$. For $\tau \to \mu \gamma$, we define the “BSM benchmark” by setting the extra top Yukawa coupling as ${\rho }_{tt}=1(\cong {\lambda }_t)$ in two-loop diagrams, and we set $\cos \gamma =0$ to decouple $h$. We show that this leading effect, which is due to $H$ and $CP$-odd scalars $A$, can be readily probed by Belle II, even for the conservative value of ${\rho }_{\tau \mu }=0.7{\lambda }_{\tau }$. We define the subleading “$h$ benchmark” by setting ${\rho }_{tt}=0$ in two-loop diagrams, and we take the conservative maximal value of $\cos \gamma =0.2$. We show that it falls beyond the reach of Belle II but can interfere with the BSM-benchmark effect, which, in principle, probes the phase of ${\rho }_{tt}$. We further show that the one-loop $H$, $A$ effect, proportional to ${\rho }_{\tau \mu }{\rho }_{\tau \tau }$ in amplitude, is beyond the sensitivity of Belle II to probe, even for ${\rho }_{\tau \tau }$ as large as $3{\lambda }_{\tau }$. With the working assumption that ${\rho }_{32}^f,{\rho }_{33}^f=\mathcal{O}({\lambda }_3^f)$ for all charged fermions $f$, we find a good discovery potential for both $\tau$ lepton flavor violation searches in the coming decade.

Elucidating the phase diagram of lattice gauge theories with fermionic matter in $2+1$ dimensions has become a problem of considerable interest in recent years, motivated by physical problems ranging from chiral symmetry breaking in high-energy physics to fractionalized phases of strongly correlated materials in condensed matter physics. For a sufficiently large number $N_f$ of flavors of four-component Dirac fermions, recent sign-problem-free quantum Monte Carlo studies of lattice quantum electrodynamics (${\mathrm{QED}}_3$) on the square lattice have found evidence for a continuous quantum phase transition between a power-law correlated conformal ${\mathrm{QED}}_3$ phase and a confining valence-bond-solid phase with spontaneously broken point-group symmetries. The critical continuum theory of this transition was shown to be the $O(2)$ ${\mathrm{QED}}_3$-Gross-Neveu model, equivalent to the gauged Nambu–Jona-Lasinio model, and critical exponents were computed to first order in the large-$N_f$ expansion and the $\epsilon$ expansion. We extend these studies by computing critical exponents to second order in the large-$N_f$ expansion and to four-loop order in the $\epsilon$ expansion below four spacetime dimensions. In the latter context, we also explicitly demonstrate that the discrete ${\mathbb{Z}}_4$ symmetry of the valence-bond-solid order parameter is dynamically enlarged to a continuous $O(2)$ symmetry at criticality for all values of $N_f$.

We study the semileptonic decays of ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }(n){\ell }^{+}{\nu }_{\ell }$ in two relativistic dynamical approaches of the light-front constituent quark model (LFCQM) and MIT bag model (MBM). By considering the Fermi statistic between quarks and determining spin-flavor structures in baryons along with the helicity formalism in the two different dynamical models, we calculate the branching ratios ($\mathcal{B}\mathrm{s}$) and averaged asymmetry parameters ($\alpha \mathrm{s}$) in the decays. Explicitly, we find that $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e)=(3.36\pm 0.87,3.48)\%$ and $\alpha ({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e)=(-0.97\pm 0.03,-0.83)$ in (LFCQM, MBM), in comparison with the data of $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e)=(3.6\pm 0.4)\%$ and $\alpha ({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e)=-0.86\pm 0.04$ given by the Particle Data Group, respectively. We also predict that $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to n{e}^{+}{\nu }_e)=(0.57\pm 0.15,3.6\pm 1.5)\times {10}^{-3}$ and $\alpha ({\mathrm{\Lambda }}_c^{+}\to n{e}^{+}{\nu }_e)=(-0.98\pm 0.02,-0.96\pm 0.04)$ in LFCQM with two different scenarios for the momentum distributions of quarks in the neutron and $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to n{e}^{+}{\nu }_e)=0.279\times {10}^{-2}$ and $\alpha ({\mathrm{\Lambda }}_c^{+}\to n{e}^{+}{\nu }_e)=-0.87$ in MBM, which could be tested by the ongoing experiments at BESIII, LHCb, and BELLEII.

We conduct a study of the interaction of the $\overline{K}{\mathrm{\Xi }}^{*}$, $\eta \mathrm{\Omega }(s\text{−}\mathrm{wave})$, and $\overline{K}\mathrm{\Xi }(d\text{−}\mathrm{wave})$ channels within a coupled channel unitary approach where the transition potential between the $\overline{K}{\mathrm{\Xi }}^{*}$ and $\eta \mathrm{\Omega }$ channels is obtained from chiral Lagrangians. The transition potential between $\overline{K}{\mathrm{\Xi }}^{*}$, $\eta \mathrm{\Omega }$, and $\overline{K}\mathrm{\Xi }$ is taken in terms of free parameters, which together with a cutoff to regularize the meson-baryon loops are fitted to the $\mathrm{\Omega }(2012)$ data. We find that all data including the recent Belle experiment on ${\mathrm{\Gamma }}_{{\mathrm{\Omega }}^{*}\to \pi \overline{K}\mathrm{\Xi }}/{\mathrm{\Gamma }}_{{\mathrm{\Omega }}^{*}\to \overline{K}\mathrm{\Xi }}$, are compatible with the molecular picture stemming from meson baryon interaction of these channels.

Identifying jets formed in high-energy particle collisions requires solving optimization problems over potentially large numbers of final-state particles. In this work, we consider the possibility of using quantum computers to speed up jet clustering algorithms. Focusing on the case of electron-positron collisions, we consider a well-known event shape called thrust whose optimum corresponds to the most jetlike separating plane among a set of particles, thereby defining two hemisphere jets. We show how to formulate thrust both as a quantum annealing problem and as a Grover search problem. A key component of our analysis is the consideration of realistic models for interfacing classical data with a quantum algorithm. With a sequential computing model, we show how to speed up the well-known $O(N^3)$ classical algorithm to an $O(N^2)$ quantum algorithm, including the $O(N)$ overhead of loading classical data from $N$ final-state particles. Along the way, we also identify a way to speed up the classical algorithm to $O(N^2\log N)$ using a sorting strategy inspired by the siscone jet algorithm, which has no natural quantum counterpart. With a parallel computing model, we achieve $O(N\log N)$ scaling in both the classical and quantum cases. Finally, we consider the generalization of these quantum methods to other jet algorithms more closely related to those used for proton-proton collisions at the Large Hadron Collider.

Assuming a certain continuity property, we prove, using the old results of Itzykson and Martin, that, except for an obvious ambiguity, there are only at most two amplitudes reproducing an elastic differential cross section at a given energy.

The gluon transversity distribution in the deuteron is defined by the matrix element between linearly polarized deuteron states, and it could be investigated in proton-deuteron collisions in addition to lepton-deuteron scattering. The linear polarization of photon is often used, whereas it is rarely used for the spin-1 deuteron. Therefore, it is desirable to express deuteron-reaction cross sections in term of conventional deuteron spin polarizations for actual experimental measurements. In this work, we investigate how proton-deuteron Drell-Yan cross sections are expressed by the conventional polarizations for finding the gluon transversity distribution. In particular, we show that the gluon transversity can be measured in the proton-deuteron Drell-Yan process by taking the cross section difference between the deuteron spin polarizations along the two-transverse axes. Since the gluon transversity does not exist for the spin-$1/2$ nucleons, a finite gluon transversity of the deuteron could indicate an “exotic” mechanism beyond the simple bound system of the nucleons in the deuteron. Therefore, the gluon transversity is an interesting and appropriate observable to shed light on a new hadronic mechanism in nuclei.

The $2\nu$-mediated force has a range of microns, well beyond the atomic scale. The effective potential is built from the $t$-channel absorptive part of the scattering amplitude and depends on neutrino properties on shell. We demonstrate that neutral aggregate matter has a weak charge and calculate the matrix of six coherent charges for its interaction with definite-mass neutrinos. Near the range of the potential the neutrino pair is nonrelativistic, leading to observable absolute mass and Dirac/Majorana distinction via different $r$-dependence and violation of the weak equivalence principle.

The nonperturbative renormalization group has been considered as a solid framework to investigate fixed point and critical exponents for matrix and tensor models, expected to correspond with the so-called double scaling limit. In this paper, we focus on matrix models and address the question of the compatibility between the approximations used to solve the exact renormalization group equation and the modified Ward identities coming from the regulator. We show in particular that standard local potential approximation strongly violates the Ward identities, especially in the vicinity of the interacting fixed point. Extending the theory space including derivative couplings, we recover an interacting fixed point with a critical exponent not so far from the exact result, but with a nonzero value for derivative couplings, evoking a strong dependence concerning the regulator. Finally, we consider a modified regulator, allowing to keep the flow not so far from the ultralocal region and recover the results of the literature up to a slight improvement.

Soft operators are (roughly speaking) zero energy massless particles which live on the celestial sphere in Minkowski space. The Lorentz group acts on the celestial sphere by conformal transformation and the soft operators transform as conformal primary operators of various dimension and spin. Working in space-time dimensions $D=4$ and 6, in this paper, we study some properties of the conformal representations with (leading) soft photon and graviton as the highest weight operators. Typically these representations contain null vectors. We argue, from the $S$-matrix point of view, that infinite dimensional asymptotic symmetries and conformal invariance require us to set these null vectors to zero. As a result, the corresponding soft operator satisfies linear partial differential equation (PDE) on the celestial sphere. Curiously, these PDEs are equations of motion of Euclidean gauge theories on the celestial sphere with scalar gauge invariance, i.e., the gauge parameter is a scalar field on the sphere. These are probably related to large $U(1)$ and supertranslation transformations at infinity. Now, the PDE satisfied by the soft operator can be converted into PDE for the $S$-matrix elements with the insertion of the soft operator. These equations can then be solved subject to appropriate boundary conditions on the celestial sphere, provided by (Lorentz) conformal invariance. The resulting soft $S$-matrix elements have an interesting “pure-gauge” form and are determined in terms of a single scalar function. Heuristically speaking, the role of the null state decoupling is to reduce the number of degrees of freedom or polarization states of soft photon and graviton to one, given effectively by a single scalar function. This reduction in the number of degrees of freedom makes the Ward identity for the asymptotic symmetry almost integrable. The result of the integration, which we are not able to perform completely, should of course be Weinberg’s soft theorem. Finally, we comment on the resemblance of all of these things to quantization of fundamental strings.

Nonrelativistic quantum mechanics with a generalized uncertainty principle (GUP) is examined in $d$-dimensional free particle and harmonic oscillator systems. The Feynman propagators for these systems are exactly derived within the first order of the GUP parameter.

We investigate the conditions for the (in)stability of the isotropic pressure condition in collapsing spherically symmetric, dissipative fluid distributions. It is found that dissipative fluxes, and/or energy density inhomogeneities and/or the appearance of shear in the fluid flow, force any initially isotropic configuration to abandon such a condition, generating anisotropy in the pressure. To reinforce this conclusion we also present some arguments concerning the axially symmetric case. The consequences of our results are analyzed.

The hybrid Higgs inflation model is a hybrid type of the so-called Higgs inflation model with the conventional nonminimal $\xi$ coupling to a scalar curvature $R$ and the new Higgs inflation model with the derivative coupling to the Einstein curvature tensor $G_{\mu \nu }$. This model can explain all possible values of the tensor-to-scalar ratio $r$ allowed by the present cosmic microwave background constraints with an appropriate choice of coupling parameters. However, the derivative coupling may cause a gradient instability during the oscillation phase after inflation just as in the new Higgs inflation model. Analyzing the behavior of perturbations during the oscillation phase in the hybrid Higgs inflation model, we show that the unstable scalar modes found in the new Higgs inflation model are stabilized by the nonminimal $\xi$ coupling for some range of the coupling parameters.

We examine the growth of structure in three different cosmological models with interacting dark matter and vacuum energy. We consider the case of geodesic dark matter with zero sound speed, where the relativistic growing mode in comoving-synchronous gauge coincides with the Newtonian growing mode at first order in $\mathrm{\Lambda }\mathrm{CDM}$. We study corrections to the linearly growing mode in the presence of interactions and the linear matter growth rate, $f_1$, contrasting this with the velocity divergence, $f_{\mathrm{rsd}}{\sigma }_8$, observed through redshift-space distortions. We then derive second-order density perturbations in these interacting models. We identify the reduced bispectrum that corresponds to the nonlinear growth of structure and show how the shape of the bispectrum is altered by energy transfer to or from the vacuum. Thus the bispectrum, or higher-order correlators, might in future be used to identify dark matter interactions.

In this paper, we investigate the asymptotic dynamics of inflationary cosmological models that are based in scalar-tensor theories of gravity. Our main aim is to explore the global structure of the phase space in the framework of single-field inflation models. For this purpose, we emphasize the adequate choice of the variables of the phase space. Our results indicate that, although single-field inflation is generic in the sense that the corresponding critical point in the phase space exists for a wide class of potentials, along given phase space orbits—representing potential cosmic histories—the occurrence of the inflationary stage is rather dependent on the initial conditions. We have been able to give quantitative estimates of the relative probability (RP) for initial conditions leading to slow-roll inflation. For the nonminimal-coupling model with the ${\varphi }^2$ potential, our rough estimates yield an almost vanishing relative probability: ${10}^{-13}\%\lesssim \mathrm{RP}\ll {10}^{-8}\%$. These bonds are greatly improved in the scalar-tensor models, including the Brans-Dicke theory, where the relative probability $1\%\lesssim \mathrm{RP}\le 100\%$. Hence, slow-roll inflation is indeed a natural stage of the cosmic expansion in Brans-Dicke models of inflation. It is confirmed as well that the dynamics of vacuum Brans-Dicke theories with arbitrary potentials are nonchaotic.

Paleodetectors are a proposed experimental technique in which one would search for traces of recoiling nuclei in ancient minerals. Natural minerals on Earth are as old as $\mathcal{O}(1)\mathrm{Gyr}$ and, in many minerals, the damage tracks left by recoiling nuclei are also preserved for timescales long compared to 1 Gyr once created. Thus, even reading out relatively small target samples of order 100 g, paleodetectors would allow one to search for very rare events thanks to the large exposure, $ϵ\sim 100\mathrm{g}\mathrm{Gyr}={10}^5\mathrm{t}\mathrm{yr}$. Here, we explore the potential of paleodetectors to measure nuclear recoils induced by neutrinos from Galactic core collapse supernovae. We find that they would not only allow for a direct measurement of the average core collapse supernova rate in the Milky Way, but would also contain information about the time dependence of the local supernova rate over the past $\sim 1\mathrm{Gyr}$. Since the supernova rate is thought to be directly proportional to the star formation rate, such a measurement would provide a determination of the local star formation history. We investigate the sensitivity of paleodetectors to both a smooth time evolution and an enhancement of the core collapse supernova rate on relatively short timescales, as would be expected for a starburst period in the local group.