The short-range part of the neutrinoless double beta amplitude is generated via the exchange of exotic particles, such as charged scalars, leptoquarks and/or diquarks. In order to give a sizable contribution to the total decay rate, the masses of these exotics should be of the order of (at most) a few TeV. Here, we argue that these exotics could be the “light” (i.e., weak-scale) remnants of some $B-L$ violating variants of $SU(5)$. We show that unification of the standard model gauge couplings, consistent with proton decay limits, can be achieved in such a setup without the need to introduce supersymmetry. Since these nonminimal $SU(5)$-inspired models violate $B-L$, they generate Majorana neutrino masses and therefore make it possible to explain neutrino oscillation data. The light colored particles of these models can potentially be observed at the LHC, and it might be possible to probe the origin of the neutrino masses with $\mathrm{\Delta }L=2$ violating signals. As particular realizations of this idea, we present two models, one for each of the two possible tree-level topologies of neutrinoless double beta decay.

We analyze the Large Hadron Collider (LHC) phenomenology of heavy vector resonances with a $SU(2{)}_L\times SU(2{)}_R$ spectral global symmetry. This symmetry partially protects the electroweak $S$ parameter from large contributions of the vector resonances. The resulting custodial vector model spectrum and interactions with the standard model fields lead to distinct signatures at the LHC in the diboson, dilepton, and associated Higgs channels.

At the LHC, tagging boosted heavy particle resonances which decay hadronically, such as top quarks and Higgs bosons, can play an essential role in new physics searches. In events with high multiplicity, however, the standard approach to tag boosted resonances by a large-radius fat jet becomes difficult because the resonances are not well separated from other hard radiation. In this paper, we propose a different approach to tag and reconstruct boosted resonances by using the recently proposed mass-jump jet algorithm. A key feature of the algorithm is the flexible radius of the jets, which results from a terminating veto that prevents the recombination of two hard prongs if their combined jet mass is substantially larger than the masses of the separate prongs. The idea of collecting jets in “buckets” is also used. As an example, we consider the fully hadronic final state of pair-produced vectorlike top partners at the LHC, $pp\to T\overline{T}\to t\overline{t}HH$, and show that the new approach works well. We also show that tagging and kinematic reconstruction of boosted top quarks and Higgs bosons are possible with good quality even in these very busy final states. The vectorlike top partners are kinematically reconstructed, which allows their direct mass measurement.

The supersymmetric custodial triplet model adds to the particle content of the minimal supersymmetric standard model three $SU(2{)}_L$ triplet chiral superfields with hypercharge $Y=(0,\pm 1)$. At the superpotential level, the model respects a global $SU(2{)}_L\otimes SU(2{)}_R$ symmetry only broken by the Yukawa interactions. The pattern of vacuum expectation values of the neutral doublet and triplet scalar fields depends on the symmetry pattern of the Higgs soft breaking masses. We study the cases in which this symmetry is maintained in the Higgs sector and in which it is broken only by the two doublets attaining different vacuum expectation values. In the former case, the symmetry is spontaneously broken down to the vectorial subgroup $SU(2{)}_V$, and the $\rho$ parameter is protected by the custodial symmetry. However, in both situations, the $\rho$ parameter is protected at tree level, allowing for light triplet scalars with large vacuum expectation values. We find that over a large range of parameter space a light neutralino can supply the correct relic abundance of dark matter either through resonant s-channel triplet scalar funnels or well tempering of the Bino with the triplet fermions. Direct detection experiments have trouble probing these model points because the custodial symmetry suppresses the coupling of the neutralino and the $Z$, and a small Higgsino component of the neutralino suppresses the coupling with the Higgs. Likewise, the annihilation cross sections for indirect detection lie below the Fermi-LAT upper bounds for the different channels.

A generalized screened potential model (GSPM), recently developed to study the bottomonium spectrum, is applied to the calculation of charmonium masses and electromagnetic widths. The presence in the GSPM of more quark-antiquark bound states than in conventional nonscreened potential models, allows for the assignment of GSPM states to cataloged nonconventional $J^{++}$ charmonium resonances as well as for the prediction of new (noncataloged) $J^{++}$ states. The results obtained seem to indicate that a reasonable overall description of $J^{++}$ charmonium resonances is feasible.

One of the largest sources of systematic uncertainties in ongoing neutrino-oscillation measurements is the description of nuclear effects. Its considerable reduction is expected thanks to the dedicated studies of (anti)neutrino-nucleus interactions in the MINERvA experiment. In this article, the calculations within the spectral function approach are compared to the charged-current quasielastic cross sections reported from MINERvA. The obtained results show that the effect of final-state interactions on the (anti)muon kinematics plays a pivotal role in reproducing the experimental data.

It is well known that compactifying a space can break symmetries that are present in the covering space. In this paper we study the effects of such topological symmetry breaking on point particle motion when the particle is coupled to a massless field on the space. For a torus topology where Lorentz invariance is broken but translation invariance is maintained, particles can move at a constant velocity through the space; however, nonlocal, velocity-dependent forces arise whenever the particle is accelerated. For a topology where translation invariance is broken, such as the Klein bottle, interactions with the massless field generate an effective potential as a function of position. The potential creates special stable points in the space, and prevents constant velocity motion. The latter would appear to be the generic case. This class of effects may be applicable whenever a localized object moves through a compactified bulk, such as in brane-world cosmology, or some condensed matter systems.

We study the collective excitations of holographic quantum liquids formed in the low energy theory living at the intersection of two sets of D-branes. The corresponding field theory dual is a supersymmetric Yang-Mills theory with massless matter hypermultiplets in the fundamental representation of the gauge group which generically live on a defect of the unflavored theory. Working in the quenched (probe) approximation, we focus on determining the universal properties of these systems. We analyze their thermodynamics, the speed of first sound, the diffusion constant, and the speed of zero sound. We study the influence of temperature, chemical potential, and magnetic field on these quantities, as well as on the corresponding collisionless/hydrodynamic crossover. We also generalize the alternative quantization for all conformally ${\mathrm{AdS}}_4$ cases and study the anyonic correlators.

We use the Schwinger-Dyson equations in the presence of a thermal bath, in order to study chiral-symmetry breaking in a system of massless Dirac fermions interacting through pseudo quantum electrodynamics, in ($2+1$) dimensions. We show that there is a critical temperature $T_c$, below which chiral symmetry is broken, and a corresponding mass gap is dynamically generated, provided the coupling is above a certain, temperature dependent, critical value ${\alpha }_c$. The ratio between the energy gap and the critical temperature for this model is estimated to be $2\pi$. These results are confirmed by analytical and numerical investigations of the Schwinger-Dyson equation for the electron. In addition, we calculate the first finite-temperature corrections to the static Coulomb interaction. The relevance of this result in the realm of condensed matter systems, like graphene, is briefly discussed.

We construct the Dirac-Born-Infeld action in the context of $\mathcal{N}=1$ conformal supergravity and its possible extensions including matter couplings. We especially focus on the Volkov-Akulov constraint, which is important to avoid ghost modes from the higher derivative terms. In the case with matter couplings, we find the modified D-term potential.

We construct asymptotically free renormalization group trajectories for the generic non-Abelian Higgs model in four-dimensional spacetime. These ultraviolet-complete trajectories become visible by generalizing the renormalization/boundary conditions in the definition of the correlation functions of the theory. Though they are accessible in a controlled weak-coupling analysis, these trajectories originate from threshold phenomena which are missed in a conventional perturbative analysis relying on the deep Euclidean region. We identify a candidate three-parameter family of renormalization group trajectories interconnecting the asymptotically free ultraviolet regime with a Higgs phase in the low-energy limit. We provide estimates of their low-energy properties in the light of a possible application to the standard model Higgs sector. Finally, we find a two-parameter subclass of asymptotically free Coleman-Weinberg-type trajectories that do not suffer from a naturalness problem.

We revisit the modeling of the properties of the remnant black hole resulting from the merger of a black-hole binary as a function of the parameters of the binary. We provide a set of empirical formulas for the final mass, spin, and recoil velocity of the final black hole as a function of the mass ratio and individual spins of the progenitor. In order to determine the fitting coefficients for these formulas, we perform a set of 128 new numerical evolutions of precessing, unequal-mass black-hole binaries, and fit to the resulting remnant mass, spin, and recoil. In order to reduce the complexity of the analysis, we chose configurations that have one of the black holes spinning, with dimensionless spin $\alpha =0.8$, at different angles with respect to the orbital angular momentum, and the other nonspinning. In addition to evolving families of binaries with different spin-inclination angles, we also evolved binaries with mass ratios as small as $q=M_1/M_2=1/6$. We use the resulting empirical formulas to predict the probabilities of black hole mergers leading to a given recoil velocity, total radiated gravitational energy, and final black hole spin.

We investigate the flux compactification mechanism in simple toy models of Einstein–Born–Infeld theories. These are the direct generalizations of the Einstein–Maxwell flux compactifications that recently gained fame as a toy model for tunneling in the landscape. Our investigation reveals that the Born–Infeld form does not significantly modify the qualitative result of the Einstein–Maxwell theory. For the case of Einstein–Higgs theory, however, we found that the effect of Born–Infeld nonlinearity is to render all $q>1$ extradimensional compactification unstable against semiclassical tunneling to nothing.

No-hair-like relations between the multipole moments of the exterior gravitational field of neutron stars have recently been found to be approximately independent of the star’s internal structure. This approximate equation-of-state universality arises after one adimensionalizes the multipole moments appropriately, which then begs the question of whether there are better ways to adimensionalize the moments to obtain stronger universality. We here investigate this question in detail by considering slowly rotating neutron stars to quartic order in spin, an approximation that is valid for spin frequencies roughly below 500 Hz, both in the nonrelativistic limit and in full general relativity. We find that there exist normalizations that lead to stronger equation-of-state universality in the relations among the moment of inertia and the quadrupole, octopole and hexadecapole moments of neutron stars. We determine the optimal normalization that minimizes the equation-of-state dependence in these relations. The results found here may have applications in the modeling of x-ray pulses and atomic line profiles from millisecond pulsars with NICER and LOFT.

In this paper we establish a formalism for the computation of observables due to acceleration-induced particle physics processes. General expressions for the transition rate, multiplicity, power, spectra, and displacement law of particles undergoing time-dependent acceleration and transitioning into a final state of arbitrary particle number are obtained. The transition rate, power, and spectra are characterized by unique polynomials of multiplicity and thermal distributions of both bosonic and fermionic statistics. The acceleration-dependent multiplicities are computed in terms of the branching fractions of the associated inertial processes. The displacement law of the spectra predicts that the energy of the emitted particles is directly proportional to the accelerated temperature.

The existence of the Unruh effect is often understood from the property of the two-point function along the Rindler trajectory where it satisfies Kubo-Martin-Schwinger (KMS) condition. In particular, it exhibits the so-called KMS periodicity along the imaginary time direction. The corresponding period is then identified with the reciprocal of the Unruh temperature times the Boltzmann constant. We show here that the two-point function including leading-order perturbative corrections due to polymer quantization—the quantization method used in loop quantum gravity—violates the KMS condition in the low-energy regime. This violation is caused by correction terms which are not Lorentz invariants. Consequently, the polymer-corrected two-point function along the Rindler trajectory looses its thermal interpretation. We discuss its implications on the existence of the Unruh effect in the context of polymer quantization.

We present a nonlinear post-Friedmann framework for structure formation, generalizing to cosmology the weak-field (post-Minkowskian) approximation, unifying the treatment of small and large scales. We consider a universe filled with a pressureless fluid and a cosmological constant $\mathrm{\Lambda }$, the theory of gravity is Einstein’s general relativity and the background is the standard flat $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model. We expand the metric and the energy-momentum tensor in powers of $1/c$, keeping the matter density and peculiar velocity as exact fundamental variables. We assume the Poisson gauge, including scalar and tensor modes up to $1/c^4$ order and vector modes up to $1/c^5$ terms. Through a redefinition of the scalar potentials as a resummation of the metric contributions at different orders, we obtain a complete set of nonlinear equations, providing a unified framework to study structure formation from small to superhorizon scales, from the nonlinear Newtonian to the linear relativistic regime. We explicitly show the validity of our scheme in the two limits: at leading order we recover the fully nonlinear equations of Newtonian cosmology; when linearized, our equations become those for scalar and vector modes of first-order relativistic perturbation theory in the Poisson gauge. Tensor modes are nondynamical at the $1/c^4$ order we consider (gravitational waves only appear at higher order): they are purely nonlinear and describe a distortion of the spatial slices determined at this order by a constraint, quadratic in the scalar and vector variables. The main results of our analysis are as follows: (a) at leading order a purely Newtonian nonlinear energy current sources a frame-dragging gravitomagnetic vector potential, and (b) in the leading-order Newtonian regime and in the linear relativistic regime, the two scalar metric potentials are the same, while the nonlinearity of general relativity makes them different. Possible applications of our formalism include the calculations of the vector potential [1,2] and the difference between the two scalar potentials from Newtonian N-body simulations, and the extension of Newtonian approximations used in structure formation studies, to include relativistic effects.

The large-scale power deficit in the cosmic microwave background fluctuations might be relevant with the physics of preinflation, a bounce, or a superinflationary phase preceding slow-roll inflation, which can provide a singular-free realization of inflation. We investigate the primordial perturbations from such preinflationary evolutions, which generally may consist of multiple phases with different background dynamics, and give a universal formula for the power spectrum of primordial perturbations in terms of the recursive Bogoliubov coefficients. We also apply our formula to corresponding cases and show how the intensity of large-scale power suppression is affected by the preinflationary physics.

Axions in the Peccei-Quinn (PQ) mechanism provide a promising solution to the strong $CP$ problem in the standard model of particle physics. Coherently generated PQ scalar fields could dominate the energy density in the early Universe and decay into relativistic axions, which would conflict with the current dark radiation constraints. We study the possibility that a thermal inflation driven by a $U(1)$ gauged Higgs field dilutes such axions. A well-motivated extra gauged $U(1)$ would be the local $B-L$ symmetry. We also discuss the implication for the case of $U(1{)}_{B-L}$ and an available baryogenesis mechanism in such cosmology.

Possible existence of baryo-dense (BD) stars and antistars, which might be created in the very early Universe in the frameworks of a slightly modified Affleck–Dine scenario of baryogenesis is studied. We discuss phenomenology, observational manifestations, and bounds on such antistars and show that they are allowed to be abundant in the Galaxy. New constraints on the possible number of compact antimatter objects are derived. We point out that explosion of an antistar as a type Ia supernova produces a remnant with relatively low annihilation signal. Another important conclusion is the strong reduction of the annihilation flux from antistars in the gaseous disk of the Galaxy due to the high velocities of BD stars in general, and antistars in particular. The contemporary observational data do not exclude significant amount of antimatter in the Galaxy (and in other galaxies) in the form of the BD stars with relatively low mass.