Form factors of the energy-momentum tensor (EMT) can be interpreted in certain frames in terms of spatial distributions of energy, stress, linear and angular momentum, based on 2D or 3D Fourier transforms. This interpretation is in general subject to “relativistic recoil corrections,” except when the nucleon moves at the speed of light like e.g. in the infinite-momentum frame. We show that it is possible to formulate a large-$N_c$ limit in which the probabilistic interpretation of the nucleon EMT distributions holds also in other frames. We use the bag model formulated in the large-$N_c$ limit as an internally consistent quark model framework to visualize the information content associated with the 2D EMT distributions. In order to provide more intuition, we present results in the physical situation and in three different limits: by considering a heavy-quark limit, a large system-size limit and a constituent-quark limit. The visualizations of the distributions in these extreme limits will help to interpret the results from experiments, lattice QCD, and other models or effective theories.

We investigate the electromagnetic response of a viscous quark-gluon plasma in the framework of the relativistic Boltzmann equation with current conserving collision term. Our formalism incorporates dissipative effects at all orders in linear response to the electromagnetic field while accounting for the full space and time dependence of the perturbing fields. As an example, we consider the collision of two nuclei in a stationary, homogeneous quark-gluon plasma. We show that for large collision energies the induced magnetic fields are governed by the response of quark-gluon plasma along the light cone. In this limit, we derive an analytic expression for the magnetic field along the beam axis between the receding nuclei and show that its strength varies only weakly with collision energy for $\sqrt{s_{\mathrm{NN}}}\ge 30\mathrm{GeV}$.

The Roper resonance, the first excited state of the nucleon, is one of the best established baryon resonances. Yet, its properties have not been consistently explained by effective models of QCD, such as the nonrelativistic quark model. In this paper, we propose an alternative approach in the Sakai-Sugimoto model that is one of the holographic models of QCD. In particular, we analyze the helicity amplitude of the electromagnetic transitions at the leading of ’t Hooft coupling $1/\lambda$. The model incorporates baryon structure at short distance by nonlinear mesons surrounded by meson clouds at long distance. We demonstrate that the recently observed data by CLAS are explained in the present approach.

We compute the differential decay width of two- and three-body neutrino decays, assuming neutrinos are Dirac fermions and allowing for the possibility that the decay-daughters have nonzero masses. We examine different hypotheses for the interaction that mediates neutrino decay and concentrate on identifying circumstances where the decay-daughters can significantly impact the neutrino-decay signature at different experiments. We are especially interested in decay daughters produced by right-chiral neutrino fields, when the mass of the daughter plays a decisive role. As a concrete example, we compare the effects of visible and invisible antineutrino decays at the JUNO experimental setup.

We show that to cubic order double field theory is encoded in Yang-Mills theory. To this end we use algebraic structures from string field theory as follows: The $L_{\infty }$-algebra of Yang-Mills theory is the tensor product $\mathcal{K}\otimes \mathfrak{g}$ of the Lie algebra $\mathfrak{g}$ of the gauge group and a “kinematic algebra” $\mathcal{K}$ that is a $C_{\infty }$-algebra. This structure induces a cubic truncation of an $L_{\infty }$-algebra on the subspace of level-matched states of the tensor product $\mathcal{K}\otimes \overline{\mathcal{K}}$ of two copies of the kinematic algebra. This $L_{\infty }$-algebra encodes double field theory. More precisely, this construction relies on a particular form of the Yang-Mills $L_{\infty }$-algebra following from string field theory or from the quantization of a suitable worldline theory.

We study the stability of an asymptotically flat, static, spherically symmetric naked singularity spacetime in the novel four-dimensional Einstein-Gauss-Bonnet (EGB) gravity. The four-dimensional EGB black hole for large enough values of the coupling parameter leads to such a naked singularity. The stability and the response of the spacetime are studied against the perturbations by test scalar, electromagnetic and Dirac fields, and the time evolution of these perturbations was observed numerically. Implementing a null Dirichlet boundary condition near the singularity, we observed that for $l=1$ modes of scalar, electromagnetic perturbation, and $l=0$, 1 modes of Dirac perturbation, the time-domain profiles give rise to distinct echoes. However, as the coupling constant increases, the echoes align, and the quasinormal mode structure of the 4D-EGB naked singularity-spacetime becomes prominent. For higher values of the multipole number, the spacetime becomes unstable, thereby restricting the parameter space for the coupling parameter.

We consider a proposal to define the wave function of the Universe as a sum over spacetimes that eventually inflate. In the minisuperspace model, we explicitly show that a simple family of initial conditions, parametrized by a positive real number $a_0$, can be imposed to realize this prescription. The resulting wave function is found to be proportional to the Hartle-Hawking wave function and its dependence on $a_0$ is only through an overall phase factor. Motivated by this observation, we ask whether it is possible to analytically extend $a_0$ to an extended region $\overline{\mathcal{D}}$ in complex $a_0$ plane, while retaining the Hartle-Hawking form of the wave function. We use the condition for convergence of path integral and a recent theorem due to Kontsevich and Segal, further extended by Witten, to explicitly find $\overline{\mathcal{D}}$. Interestingly, a special point on the boundary of $\overline{\mathcal{D}}$ recovers the exact no-boundary wave function. Following that, we show that our prescription leads to a family of quantum states for the perturbations, which give rise to scale-invariant power spectra. If we demand, as an extra ingredient to our prescription, a matching condition at the “no-boundary point” in $\overline{\mathcal{D}}$, we converge on a unique quantum state for the perturbations.

We study the magnetic field generation from the cosmological first-order electroweak phase transition. We calculate the magnetic fields induced by the variation of the Higgs phase for two-bubble and three-bubble collisions, and find that the generated magnetic field strength with the effect of bubble shape distortion is about half of that derived without including the shape deformation. Our study shows that electromagnetic currents in the collision direction produce the ringlike magnetic field in the intersection area of colliding bubbles, which has a chance to seed the primordial magnetic field constrained by intergalactic magnetic field observations.

Features such as photon rings, jets, or hot spots can leave particular topological signatures in a black hole image. As such, topological data analysis can be used to characterize images resulting from high-resolution observations (synthetic or real) of black holes in the electromagnetic sector. We demonstrate that persistent homology allows for this characterization to be made automatically by counting the number of connected components and one-dimensional holes. Further, persistent homology also allows for the distance between connected components or the diameter of holes to be extracted from the image. In order to apply persistent homology on synthetic black hole images, we also introduce metronization, a new algorithm to prepare black hole images in a form that is suitable for topological analysis.

The sensitivity of ongoing searches for gravitational wave (GW) sources in the ultra-low-frequency regime (${10}^{-9}\mathrm{Hz}$ to ${10}^{-7}\mathrm{Hz}$) using pulsar timing arrays (PTAs) will continue to increase in the future as more well-timed pulsars are added to the arrays. It is expected that next-generation radio telescopes, namely, the Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) and the Square Kilometer Array (SKA), will grow the number of well-timed pulsars to $O({10}^3)$. The higher sensitivity will result in greater distance reach for GW sources, uncovering multiple resolvable GW sources in addition to an unresolved population. Data analysis techniques that can search for and resolve multiple signals present simultaneously in PTA data are, therefore, required. The multisource resolution problem in PTA data analysis poses a unique set of challenges such as nonuniformly sampled data, a large number of so-called pulsar phase parameters that arise from the inaccurately measured distances to the pulsars, and poor separation of signals in the Fourier domain due to a small number of cycles in the observed waveforms. We present a method that can address these challenges and demonstrate its performance on simulated data from PTAs with ${10}^2$ to ${10}^3$ pulsars. The method estimates and subtracts sources from the data iteratively using multiple stages of refinement, followed by a step that mitigates spurious identified sources by comparing the outputs from two different algorithms. The performance of the method compares favorably with the global fit approaches that have been proposed so far. In all the cases tested in this work, the fraction of sources found by the method that correspond to true sources in the simulated data exceeds 78% and 93% for a large-scale (with ${10}^3$ pulsars and 200 sources) and a midscale (with ${10}^2$ pulsars and 100 sources) PTA, respectively. The network signal-to-noise ratio of the recovered true sources reaches down to 16.43 for the large-scale and 9.07 for the midscale PTA.

The possibility of neutron swapping between the ordinary and mirror sectors is today a subject of a great many theoretical and experimental studies. In this paper, we investigate the neutron-mirror neutron transitions in different environments from a vacuum to a neutron star. Our approach is based on the density matrix formalism, Lindblad and Bloch equations and the implication of the seesaw mechanism to the Hamiltonian diagonalization.

The recent results from the Fermilab muon $g-2$ experiment, as well as the persisting hints of lepton flavor universality violation in $B$-meson decays, present a very strong case for flavor-nonuniversal new physics beyond the Standard Model. We assert that a minimal $R$-parity violating supersymmetric scenario with relatively light third-generation sfermions (dubbed as “RPV3”) provides a natural, well-motivated framework for the simultaneous explanation of all flavor anomalies, while being consistent with a multitude of low-energy flavor constraints, as well as with limits from high-energy collider searches. We further propose complementary tests and distinct signatures of this scenario in the high-$p_T$ searches at current and future colliders. Specifically, we find that an sbottom in the mass range of 2–12 TeV accounts for $R_{D^{(*)}}$ and $R_{K^{(*)}}$ flavor anomalies and it only plays a minor role in the $(g-2{)}_{\mu }$ anomaly, whereas a sneutrino with mass between 0.7–1 TeV is the dominant player for $(g-2{)}_{\mu }$. In this context, we propose specific collider signatures of sbottom via its decays to $\overline{t}(t){\mu }^{+}{\mu }^{-}$, and of sneutrino pairs with their decays leading to a highly distinctive and spectacular four-muon final state, which can be used to completely probe the RPV3 parameter space of interest.

We propose a model of Majorana fermions with quartic self-couplings. These Majorana fermions acquire masses via a type-II seesaw mechanism in which the physical eigenstates are identified as a light Majorana fermion and another heavy Majorana fermion. On a physical basis, the quartic self-couplings involve axial currents of these Majorana fermions, and also the interaction of the axial current for the light particle with the heavy particle one. We introduce two auxiliaries gauge fields in this model, and we study the stability conditions of the correspondent effective potential of the model. The ground state of the effective potential introduces two 4-vectors as scales of vacuum expected values, and consequently, the dynamical Lorentz symmetry breaking (DLSB) emerges in the model. We use the expansion of the effective action to calculate the effective Lagrangian up to second order in the auxiliary fields as fluctuations around the ground state. This mechanism generates dynamics for the auxiliary gauge fields, mixed mass terms, longitudinal propagation, and Chern-Simons term through radiative corrections. After the diagonalization, the two gauge fields gain masses through an analogous type-II seesaw mechanism in which a gauge boson has a light mass, and the other one acquires a heavy mass. In this scenario of Lorentz symmetry breaking, we obtain the correspondent dispersion relations for the Majorana fermions and the gauge boson fields. Posteriorly, we analyze the neutrino’s oscillations in the presence of a DLSB parameter, in the transition ${\nu }_e\to {\nu }_{\mu }$. We discuss the parameter space of this transition and show that the DLSB can conciliate the LSND and Super-Kamiokande results.

We study general freeze-out scenarios where an arbitrary number of initial and final dark matter particles participate in the number-changing freeze-out interaction. We consider a simple sector with two particle species undergoing such a thermal freeze-out; one of the relics is stable and gives rise to the dark matter today, while the other one decays to the Standard Model, injecting significant entropy into the thermal bath that dilutes the dark matter abundance. We show that this setup can lead to a stable relic population that reproduces the observed dark matter abundance without requiring weak-scale masses or couplings. The final dark matter abundance is estimated analytically. We carry out this calculation for arbitrary temperature dependence in the freeze-out process and identify the viable dark matter mass and cross section ranges that explain the observed dark matter abundance. This setup can be used to open parameter space for both heavy (above the unitarity bound) or light (sub-GeV) dark matter candidates. We point out that the best strategy for probing most parts of our parameter space is to look for signatures of an early matter-dominant epoch.

We introduce a new method to search for the dark matter sector particles using laser light. Some dark matter particles may have a small mixing or interaction with a photon. High-power lasers provide substantial test grounds for these hypothetical light particles of exploding interests in particle physics. We show that any light source can also emit a subfrequency light as a new physics signal. Searching for this subfrequency light at a laser can be a simple and effective way to investigate the new light particles, even in tabletop optics experiments.

The mass spectra and wave functions of both $1S$ and $2S$ state heavy pseudoscalar ($P$) and vector ($V$) mesons are analyzed within the light-front quark model. Important empirical constraints employed in our analysis of the mass spectra and wave functions are the experimental mass-gap relation, $\mathrm{\Delta }{M}_P>\mathrm{\Delta }{M}_V$, where $\mathrm{\Delta }{M}_{P(V)}=M_{P(V)}^{2S}-M_{P(V)}^{1S}$ and the hierarchy of the decay constants, $f_{1S}>f_{2S}$, between $1S$ and $2S$ meson states. We maintain the orthogonality of the trial wave functions of the $1S$ and $2S$ states in our variational calculation of the Hamiltonian with the Coulomb plus confining potentials and treat the hyperfine interaction perturbatively for the heavy-heavy and heavy-light $P$ and $V$ mesons due to the nature of the heavy quark symmetry. Realizing that the empirical constraints cannot be satisfied without mixing of the $1S$ and $2S$ states, we find the lower bound of the mixing angle $\theta$ between $1S$ and $2S$ states as ${\theta }_c={\cot }^{-1}(2\sqrt{6})/2\simeq 6°$ and obtain the optimum value of the mixing angle around 12° to cover both the charm and bottom flavors of the heavy quark. The mixing effects are found to be more significant to the $2S$ state mesons than to the $1S$ state mesons. The properties of $1S$ and $2S$ state mesons including the mass spectra, decay constants, twist-2 distribution amplitudes, and electromagnetic form factors are computed. Our results are found to be in a good agreement with the available data and lattice simulations. In particular, the $2S$ state pseudoscalar $D_s$ meson is predicted to have a mass of 2600 MeV, which is very close to the mass of the newly discovered $D_{s0}(2590{)}^{+}$ meson by the LHCb Collaboration. This supports the interpretation of the observed state as a radial excitation of the $D_s^{+}$ meson.

We consider the class of inclusive hadron collider processes in which several energetic jets are produced, possibly accompanied by colorless particles [such as Higgs boson(s), vector boson(s) with their leptonic decays, and so forth]. We propose a new variable that smoothly captures the $N+1$ to $N$-jet transition. This variable, that we dub $k_T^{\mathrm{ness}}$, represents an effective transverse momentum controlling the singularities of the $N+1$-jet cross section when the additional jet is unresolved. The $k_T^{\mathrm{ness}}$ variable offers novel opportunities to perform higher-order calculations in quantum chromodynamics by using nonlocal subtraction schemes. We study the singular behavior of the $N+1$-jet cross section as $k_T^{\mathrm{ness}}\to 0$ and, as a phenomenological application, we use the ensuing results to evaluate next-to-leading-order corrections to $H+\mathrm{jet}$ and $Z+2$-jet production at the LHC. We show that $k_T^{\mathrm{ness}}$ performs extremely well as a resolution variable and appears to be very stable with respect to hadronization and multiple-parton interactions.

We compute the invariants for a class of knots and links in arbitrary representations in $S^3/{\mathbb{Z}}_p$ in the large $k$ (level), large $N$ (rank) limit, keeping $N/(k+N)=\lambda$ fixed, in $U(N)$ and $Sp(N)$ Chern-Simons theories. Using the relation between the saddle-point description and collective field theory, we first find that the invariants for the Hopf link and unknot are given by the on-shell collective field theory action. We next show that the results of these two invariants can be used to compute the invariants of other torus knots and links. We also discuss the large $N$ phase structure of the Hopf link invariant and observe that the same may admit a Douglas-Kazakov type phase transition depending on the choice of representations and $\lambda$.

We consider the problem of soft scattering for the analogue of pion states in gauge-fermion theories which approach a conformal fixed point in the infrared limit. Introducing a fermion mass into such a theory will explicitly break both scale invariance and chiral symmetry, leading to confinement and a spectrum of bound states. We argue that in such a theory, the pion scattering length diverges in the limit of zero fermion mass, in sharp contrast to QCD-like theories where the chiral Lagrangian predicts a vanishing scattering length. We demonstrate this effect both with a simple dimensional argument, and in a generalized linear sigma model which we argue can be used to describe the interactions of light scalar and pseudoscalar bound states in the soft limit of a mass-deformed infrared-conformal theory. As a result, lattice calculations of pion scattering lengths could be a sensitive probe for infrared scale invariance in gauge-fermion theories.

The impact of $SU(3)$ center vortices on the Landau-gauge gluon propagator is calculated in the presence of dynamical fermions and compared to the pure Yang-Mills case. The presence of dynamical fermions is found to alter the behavior of the center vortex propagator when compared to the established pure-gauge result. The gluon spectral representation is also explored from the center vortex perspective, where center vortices are shown to exhibit clear signs of positivity violation, which is an indicator of confinement. Vortex removal subsequently restores positivity, demonstrating the crucial role center vortices play in the confinement of gluons.