The nonrelativistic quantum mechanics with a generalized uncertainty principle (GUP) is examined when the potential is a one-dimensional $\delta$-function. It is shown that unlike usual quantum mechanics, the Schrödinger and Feynman’s path-integral approaches are inequivalent at the first order of the GUP parameter.

We explore the idea to bootstrap Feynman integrals using integrability. In particular, we put the recently discovered Yangian symmetry of conformal Feynman integrals to work. As a prototypical example we demonstrate that the $D$-dimensional box integral with generic propagator powers is completely fixed by its symmetries to be a particular linear combination of Appell hypergeometric functions. In this context the Bloch-Wigner function arises as a special Yangian invariant in four dimensions. The bootstrap procedure for the box integral is naturally structured in algorithmic form. We then discuss the Yangian constraints for the six-point double box integral as well as for the related hexagon. For the latter we argue that the constraints are solved by a set of generalized Lauricella functions, and we comment on complications in identifying the integral as a certain linear combination of these. Finally, we elaborate on the close relation to the Mellin-Barnes technique and argue that it generates Yangian invariants as sums of residues.

Besides the string scale, string theory has no parameter except some quantized flux values, and the string theory Landscape is generated by scanning over discrete values of all the flux parameters present. We propose that a typical (normalized) probability distribution $P(\mathcal{Q})$ of a physical quantity $\mathcal{Q}$ (with non-negative dimension) tends to peak (diverge) at $\mathcal{Q}=0$ as a signature of string theory. In the Racetrack Kähler uplift model, where $P(\mathrm{\Lambda })$ of the cosmological constant $\mathrm{\Lambda }$ peaks sharply at $\mathrm{\Lambda }=0$, the electroweak scale (not the electroweak model) naturally emerges when the median $\mathrm{\Lambda }$ is matched to the observed value. We check the robustness of this scenario. In a bottom-up approach, we find that the observed quark and charged lepton masses are consistent with the same probabilistic philosophy, with distribution $P(m)$ that diverges at $m=0$, with the same (or almost the same) degree of divergence. This suggests that the Standard Model has an underlying string theory description, and yields relations among the fermion masses, albeit in a probabilistic approach (very different from the usual sense). Along this line of reasoning, the normal hierarchy of neutrino masses is clearly preferred over the inverted hierarchy, and the sum of the neutrino masses is predicted to be $\sum m_{\nu }\simeq 0.0592\mathrm{eV}$, with an upper bound $\sum m_{\nu }<0.066\mathrm{eV}$. This illustrates a novel way string theory can be applied to particle physics phenomenology.

In the scope of black hole spectroscopy, several attempts have been made in the past decades to test black holes or gravitational theories via black hole quasinormal modes. In the eikonal approximation, the quasinormal modes are generically associated with the photon ring of the black hole. This correspondence is valid for most cases in general relativity, but may not be true in other theories of gravity. In this paper, we consider the generalized energy-momentum squared gravity in which matter fields are nonminimally coupled to geometry. We investigate the axial perturbations of the charged black holes in this model, without assuming any explicit expression of the action functional. After obtaining the modified Klein-Gordon equation and the modified Maxwell equations, we perturb the gravitational equations and the modified Maxwell equations to derive the coupled master equations of the axial perturbations. In the presence of the nonminimal coupling between matter and geometry, the correspondence between the eikonal quasinormal modes and the photon ring is not satisfied in general. Also, the two coupled fields of the axial perturbations are found to propagate independently, and they do not share the same quasinormal frequencies in the eikonal limit.

A symmetry principle has been shown to augment unambiguously the Einstein field equations, promoting the whole closed-string massless NS-NS sector to stringy graviton fields. Here we consider its weak field approximation, take a nonrelativistic limit, and derive the stringy augmentation of Newton gravity: ${\mathbf{\nabla }}^2\mathrm{\Phi }=4\pi G\rho +\mathbf{H}·\mathbf{H}$, $\mathbf{\nabla }·\mathbf{H}=0$, $\mathbf{\nabla }\times \mathbf{H}=4\pi G\mathbf{K}$. Not only the mass density $\rho$ but also the current density $\mathbf{K}$ is intrinsic to matter. Sourcing $\mathbf{H}$ which is of NS-NS $H$-flux origin, $\mathbf{K}$ is nontrivial if the matter is “stringy.” $\mathbf{H}$ contributes quadratically to the Newton potential, but otherwise is decoupled from the point particle dynamics, i.e., $\ddot{\mathbf{x}}=-\mathbf{\nabla }\mathrm{\Phi }$. We define “stringization” analogous to magnetization and discuss regular as well as monopolelike singular solutions.

Using an alternative approach, we investigate critical behavior and phase transition of higher dimensional charged black holes in an anti–de Sitter background and in the presence of conformally invariant Power-Maxwell electrodynamics. In this approach, we keep the cosmological constant (pressure) as a fixed thermodynamic quantity and instead allow the charge of the black hole to vary. We disclose that one can realize the critical behavior for the system in ${\mathit{Q}}_p\text{−}\mathrm{\Psi }$ plane and deduce all the critical exponents of the system as well as calculate the critical point $(T_c,{\mathit{Q}}_{p_c},{\mathrm{\Psi }}_c)$, where ${\mathit{Q}}_p=Q^{2p/(2p-1)}$, $p$ is the power parameter of the Power-Maxwell Lagrangian, and $\mathrm{\Psi }$ is the conjugate of ${\mathit{Q}}_p$. We observe that the critical exponents are independent of the details of the model and have the same values as Van der Waals liquid-gas system. We thus complete the analogy of these types of black holes with Van der Waals liquid-gas system. We also write down the equation of state as ${\mathit{Q}}_p={\mathit{Q}}_p(T,\mathrm{\Psi })$ and construct a Smarr relation based on this new phase space as $M=M(S,P,{\mathit{Q}}_p)$. We obtain the Gibbs free energy of the system and find a swallowtail behavior in Gibbs diagrams, which is a characteristic of the first-order phase transition. Finally, we explain the microscopic behavior of the black hole by using thermodynamic geometry. We observe a gap in the scalar curvature $R$ that occurs between small and large black holes. The maximum value of this gap increases with increasing the dimension of the spacetime. It is seen that the interaction among the internal constituents of the black hole, as a thermodynamical system, is intrinsically a strong repulsive interaction.

Within the general framework of spatially covariant theories of gravity, we study the conditions for having only the two tensorial degrees of freedom. Generally, there are three degrees of freedom propagating in the theory, of which two are tensorial and one is of the scalar type. Through a detailed Hamiltonian analysis, we find two necessary and sufficient conditions to evade the scalar type degree of freedom. The first condition implies that the lapse function-extrinsic curvature sector must be degenerate. The second condition ensures that the dimension of the phase space at each spacetime point is even, so that the scalar type degree of freedom is eliminated completely. We also compare our results with the previous studies, and apply our formalism to a simple example, in which the Lagrangian is quadratic in the extrinsic curvature.

We search for an extension of the Standard Model that contains a viable dark matter candidate and that can be embedded into a fundamental, asymptotically safe, quantum field theory with quantum gravity. Demanding asymptotic safety leads to boundary conditions for the nongravitational couplings at the Planck scale. For a given dark matter model, these translate into constraints on the mass of the dark matter candidate. We derive constraints on the dark matter mass and couplings in two minimal dark matter models: (i) scalar dark matter coupled via the Higgs portal in the $B-L$ model; (ii) fermionic dark matter in a $U(1{)}_X$ extension of the Standard Model, coupled via the new gauge boson. For scalar dark matter, we find $56\mathrm{GeV}<M_{\mathrm{DM}}<63\mathrm{GeV}$, and for fermionic dark matter, $M_{\mathrm{DM}}\le 50\mathrm{TeV}$. Within our framework, we identify three benchmark scenarios with distinct phenomenological consequences.

Precision measurements of the positron flux in the cosmic ray have revealed an unexplained bump in the spectrum around $E\simeq 300\mathrm{GeV}$, not clearly attributable to known astrophysical processes. We propose annihilation of dark matter of mass $m_{\chi }=780\mathrm{GeV}$ with a late-time cross section $\sigma v=4.63\times {10}^{-24}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ as a possible source. The nonmonotonic dependence of the annihilation rate on dark matter velocity, owing to a selective $p$-wave Sommerfeld enhancement, allows such a large signal from the Milky Way without violating corresponding constraints from cosmic microwave background and dwarf galaxy observations. We briefly explore other signatures of this scenario, and outline avenues to test it in future experiments.

We systematically examine light curves from a single hot spot on a slowly rotating neutron star with very high compactness, where the so-called invisible zone does not exist. In particular, we adopt three different shapes of hot spot and take into account the finite size effect of a hot spot on the light curves. Then, we find that the brightening of flux occurs when the hot spot with small area crosses the opposite side to the observer, where the brightening becomes stronger as the area of the hot spot decreases. Since this brightening happens only when a part of hot spot crosses the opposite side to the observer, one may constrain the neutron star geometry, i.e., the combination of an inclination angle, angle between the rotational axis and normal vector at the center of the hot spot, and the opening angle of the hot spot, if the brightening would be observed. In addition, by counting such a brightening in the light curves, one may know how many narrow bands of hot spot and/or spots with small area cross the opposite side to the observer.

QCD axions or axionlike particles are among the most popular candidates for cold dark matter (DM) in the Universe. We proposed to detect axionlike DM, using linearly polarized pulsar light as a probe. Because of birefringence effect potentially caused by an oscillating galactic axion DM background, when pulsar light travels across the Galaxy, its linear polarization angle may vary with time. With a $\mathrm{soliton}+\mathrm{NFW}$ galactic DM halo profile, we show that this strategy can potentially probe an axion-photon coupling as small as $\sim {10}^{-13}{\mathrm{GeV}}^{-1}$ for axion mass $m_a\sim {10}^{-22}–{10}^{-20}\mathrm{eV}$, given the current measurement accuracy. An exclusion limit stronger than CAST ($\sim {10}^{-10}{\mathrm{GeV}}^{-1}$) and SN1987A ($\sim {10}^{-11}{\mathrm{GeV}}^{-1}$) could be extended up to $m_a\sim {10}^{-18}\mathrm{eV}$ and $\sim {10}^{-19}\mathrm{eV}$, respectively.

Gravitational wave astrophysics relies heavily on the use of matched filtering both to detect signals in noisy data from detectors and to perform parameter estimation and tests of general relativity on those signals. Matched filtering relies upon prior knowledge of the signals expected to be produced by a range of astrophysical systems, such as binary black holes. These waveform signals can be computed using numerical relativity techniques, where the Einstein field equations are solved numerically, and the signal is extracted from the simulation. Numerical relativity simulations are, however, computationally expensive, leading to the need for a surrogate model which can predict waveform signals in regions of the physical parameter space which have not been probed directly by simulation. We present a method for producing such a surrogate using Gaussian process regression which is trained directly on waveforms generated by numerical relativity. This model returns not just a single interpolated value for the waveform at a new point, but a full posterior probability distribution on the predicted value. This model is therefore an ideal component in a Bayesian analysis framework, through which the uncertainty in the interpolation can be taken into account when performing parameter estimation of signals.

We explore the in-medium properties of heavy-quarkonium states at finite baryochemical potential and finite transverse momentum based on a modern complex-valued potential model. Our starting point is a novel, rigorous derivation of the generalized Gauss law for in-medium quarkonium, combining the nonperturbative physics of the vacuum bound state with a weak coupling description of the medium degrees of freedom. Its relation to previous models in the literature is discussed. We show that our approach is able to reproduce the complex lattice QCD heavy quark potential even in the nonperturbative regime, using a single temperature dependent parameter, the Debye mass $m_D$. After vetting the Gauss law potential with state-of-the-art lattice QCD data, we extend it to the regime of finite baryon density and finite velocity, currently inaccessible to first principles simulations. In-medium spectral functions computed from the Gauss law potential are subsequently used to estimate the ${\psi }^{\prime }/J/\psi$ ratio in heavy-ion collisions at different beam energies and transverse momenta. We find qualitative agreement with the predictions from the statistical model of hadronization for the $\sqrt{s_{NN}}$ dependence and a mild dependence on the transverse momentum.

The Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix and flavor-changing neutral currents (FCNCs) in the quark sector are examined in the grand unified theory inspired $SO(5)\times U(1)\times SU(3)$ gauge-Higgs unification in which the 4D Higgs boson is identified with the Aharonov-Bohm phase in the fifth dimension. Gauge invariant brane interactions play an important role for the flavor mixing in the charged-current weak interactions. The CKM matrix is reproduced except that the up quark mass needs to be larger than the observed one. FCNCs are naturally suppressed as a consequence of the gauge invariance, with a factor of order ${10}^{-6}$. It is also shown that induced flavor-changing Yukawa couplings are extremely small.

We consider a $Z^{\prime }$ model in which the $Z^{\prime }$ boson couples only to up and top quarks. For a simple setup, one can consider a family-dependent $U(1{)}^{\prime }$ symmetry, under which only right-handed up-type quarks are charged. After symmetry breaking, the right-handed quarks mix with each other, and top flavor-changing neutral currents (FCNCs) mediated by the $Z^{\prime }$ boson can be generated at tree level. We take into account several processes at the parton level to probe the top FCNCs and find that the same-sign top quark pair production or the triple top quark production is the most capable of testing the top FCNCs. We also consider a few non-FCNC processes to probe the $Z^{\prime }$ boson, for example, dijet production at the LHC. Finally, we perform numerical analysis at detector level and find that the same-sign top quark pair production provides a much more stringent bound on the FCNC coupling than the other processes in most of the parameter space.

We explore the generation of the baryon asymmetry in an extension of the standard model where the lepton number is promoted to a $U(1{)}_{\ell }$ gauge symmetry with an associated $Z^{\prime }$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. [M. Carena, M. Quiros, and Y. Zhang, Electroweak Baryogenesis From Dark $CP$ violation, Phys. Rev. Lett. 122, 201802 (2019).]. Extra fermionic degrees of freedom, including a fermionic dark matter $\chi$, are introduced in the dark sector for anomaly cancellation. The lepton number is spontaneously broken at high scale and the effective theory, containing the standard model, the $Z^{\prime }$, the fermionic dark matter, and an additional complex scalar field $S$, violates $CP$ in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark $CP$ violation is diffused in front of the bubble walls and creates a chiral asymmetry for $\chi$, which in turn creates a chemical potential for the standard model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^{\prime }$, the dark matter candidate, the Higgs boson, and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1{)}_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.

We study the role that global and local non-Abelian symmetries play in two-dimensional (2D) lattice gauge theories with multicomponent scalar fields. We start from a maximally $\mathrm{O}(M)$-symmetric multicomponent scalar model. Its symmetry is partially gauged to obtain an $\mathrm{SU}(N_c)$ gauge theory (scalar chromodynamics) with global $\mathrm{U}(N_f)$ (for $N_c\ge 3$) or $\mathrm{Sp}(N_f)$ symmetry (for $N_c=2$), where $N_f>1$ is the number of flavors. Correspondingly, the fields belong to the coset $S^M/\mathrm{SU}(N_c)$ where $S^M$ is the $M$-dimensional sphere and $M=2N_f{N}_c$. In agreement with the Mermin-Wagner theorem, the system is always disordered at finite temperature and a critical behavior only develops in the zero-temperature limit. Its universal features are investigated by numerical finite-size scaling methods. The results show that the asymptotic low-temperature behavior belongs to the universality class of the 2D ${\mathrm{CP}}^{N_f-1}$ field theory for $N_c>2$ and to that of the 2D $\mathrm{Sp}(N_f)$ field theory for $N_c=2$. These universality classes correspond to 2D statistical field theories associated with symmetric spaces that are invariant under $\mathrm{Sp}(N_f)$ transformations for $N_c=2$ and under $\mathrm{SU}(N_f)$ for $N_c>2$. These symmetry groups are the same invariance groups of scalar chromodynamics, apart from a U(1) flavor symmetry that is present for $N_f\ge N_c>2$, which does not play any role in determining the asymptotic behavior of the model.

We investigate the single transverse-spin asymmetry with a $\sin (2\varphi -{\varphi }_S)$ modulation in the pion-induced Drell-Yan process within the theoretical framework of the transverse momentum dependent (TMD) factorization. The asymmetry is contributed by the convolution of the Boer-Mulders function and the transversity. We adopt the model results for the distributions of the pion meson and the available parametrization for the distributions of the proton to numerically estimate the $\sin (2\varphi -{\varphi }_S)$ asymmetry in ${\pi }^{-}p$ Drell-Yan at the kinematics of COMPASS at CERN. To implement the TMD evolution formalism of the distribution functions, we apply two different parametrizations on the nonperturbative Sudakov form factors associated with the distribution functions of the proton and the pion. It is found that our prediction on the single transverse-spin dependent asymmetry $\sin (2\varphi -{\varphi }_S)$ as functions of $x_p$, $x_{\pi }$, $x_F$ and $q_{\perp }$ is qualitatively consistent with the recent COMPASS measurement in both sign and magnitude.

The goal of this paper is to extend the results of [K. Kajantie, L. D. McLerran, and R. Paatelainen, Gluon radiation from a classical point particle, Phys. Rev. D 100, 054011 (2019)., where formulas were derived for gluonic radiation for a high energy nucleus colliding with a classical colored particle. In [K. Kajantie, L. D. McLerran, and R. Paatelainen, Gluon radiation from a classical point particle, Phys. Rev. D 100, 054011 (2019).], we computed the amplitudes for radiation in the fragmentation region of the particle for a dilute gluonic field. In this paper, we compute the radiation by solving the fluctuation equations of the dense background field in a specific gauge, which makes it simple to solve the asymptotic radiation from an initial condition immediately after the passage of the nucleus. We identify and compute two components of gluon radiation, a bulk component which extends to the central region and bremsstrahlung, which may give rise to an experimentally observable intensity peak in the target fragmentation region.

This paper presents results of searches for the electroweak production of supersymmetric particles in models with compressed mass spectra. The searches use $139{\mathrm{fb}}^{-1}$ of $\sqrt{s}=13\mathrm{TeV}$ proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider. Events with missing transverse momentum and two same-flavor, oppositely charged, low-transverse-momentum leptons are selected, and are further categorized by the presence of hadronic activity from initial-state radiation or a topology compatible with vector-boson fusion processes. The data are found to be consistent with predictions from the Standard Model. The results are interpreted using simplified models of $R$-parity-conserving supersymmetry in which the lightest supersymmetric partner is a neutralino with a mass similar to the lightest chargino, the second-to-lightest neutralino, or the slepton. Lower limits on the masses of charginos in different simplified models range from 193 to 240 GeV for moderate mass splittings, and extend down to mass splittings of 1.5 to 2.4 GeV at the LEP chargino bounds (92.4 GeV). Similar lower limits on degenerate light-flavor sleptons extend up to masses of 251 GeV and down to mass splittings of 550 MeV. Constraints on vector-boson fusion production of electroweak SUSY states are also presented.