In December 2015, the ATLAS and CMS collaborations presented a possible signal in the diphoton channel. Although more data have shown that the signal was likely to be only a statistical fluctuation, it is interesting to ask what can be learned if any diphoton excess would show up in future data. Here we challenge the interpretation of any possible diphoton excess in a two-Higgs-doublet framework and find results that are valid whenever a large number of colored and charged vectorlike fermions are needed to boost the production cross section. In a broad region of parameter space, the one-loop effects of these fermions abruptly drive the scalar potential to instability even before the hypercharge gauge coupling becomes nonperturbative.

More than $3\sigma$ deviations from the standard model are observed in the angular observable $P_5^{\prime }$ of $B\to K^{*}{\mu }^{+}{\mu }^{-}$ and muon $g-2$. To resolve these anomalies, we extend the standard model by adding two leptoquarks. It is found that the signal strength of the diphoton Higgs decay can exhibit a significant deviation from unity and is within the data errors. Although ${\ell }_i\to {\ell }_j\gamma$ puts severe bounds on some couplings, it is found that the excesses of $P_5^{\prime }$ and the muon $g-2$ can still be explained and accommodated to the measurement of $B_s\to {\mu }^{+}{\mu }^{-}$ in this model. In addition, the leptoquark effects can also explain the LHCb measurement of $R_K=\mathrm{BR}(B^{+}\to K^{+}{\mu }^{+}{\mu }^{-})/\mathrm{BR}(B^{+}\to K^{+}{e}^{+}{e}^{-})=0.745_{-0.074}^{+0.090}\pm 0.036$, which shows a $2.6\sigma$ deviation from the standard model prediction.

We present a chiral solution of the Ginsparg-Wilson equation. This work is motivated by our recent proposal for nonperturbatively regulating chiral gauge theories, where five-dimensional domain wall fermions couple to a four-dimensional gauge field that is extended into the extra dimension as the solution to a gradient flow equation. Mirror fermions at the far surface decouple from the gauge field as if they have form factors that become infinitely soft as the distance between the two surfaces is increased. In the limit of an infinite extra dimension we derive an effective four-dimensional chiral overlap operator which is shown to obey the Ginsparg-Wilson equation, and which correctly reproduces a number of properties expected of chiral gauge theories in the continuum.

We discuss the thermodynamics of the O(3) nonlinear sigma model in $1+1$ dimensions at nonzero chemical potential (equivalent to a magnetic field). In its conventional field theory representation the model suffers from a sign problem. By dualizing the model, we are able to fully access the nonzero density regime of an asymptotically free theory with dynamical mass gap at arbitrary chemical potential values. We find a quantum phase transition at zero temperature where as a function of the chemical potential the density assumes a nonzero value. Measuring the spin stiffness we present evidence for a corresponding dynamical critical exponent $z$ close to 2. The low energy O(3) model is conjectured to be described by a massive boson triplet with repulsive interactions. We confirm the universal square-root behavior expected for such a system at low density (and temperature) and compare our data to the results of Bethe Ansatz solutions of the relativistic and nonrelativistic one-dimensional Bose gas. We also comment on a potential Berezinskii-Kosterlitz-Thouless transition at nonzero density.

We demonstrate the applicability of a recently proposed multiscale thermalization algorithm to two-color quantum chromodynamics (QCD) with two mass-degenerate fermion flavors. The algorithm involves refining an ensemble of gauge configurations that had been generated using a renormalization group (RG) matched coarse action, thereby producing a fine ensemble that is close to the thermalized distribution of a target fine action; the refined ensemble is subsequently rethermalized using conventional algorithms. Although the generalization of this algorithm from pure Yang-Mills theory to QCD with dynamical fermions is straightforward, we find that in the latter case, the method is susceptible to numerical instabilities during the initial stages of rethermalization when using the hybrid Monte Carlo algorithm. We find that these instabilities arise from large fermion forces in the evolution, which are attributed to an accumulation of spurious near-zero modes of the Dirac operator. We propose a simple strategy for curing this problem, and demonstrate that rapid thermalization—as probed by a variety of gluonic and fermionic operators—is possible with the use of this solution. In addition, we study the sensitivity of rethermalization rates to the RG matching of the coarse and fine actions, and identify effective matching conditions based on a variety of measured scales.

We consider the $2+1$-dimensional massive Thirring model with one flavor at finite density. Two numerical methods, the fermion bag approach and complex Langevin dynamics, are used to calculate the chiral condensate and fermion density of this model. The numerical results obtained by the fermion bag approach are compared with those obtained by complex Langevin dynamics. They are also compared with those obtained under a phase-quenched approximation. We show that in some range of fermion coupling strength and chemical potential, the sign problem in the fermion bag approach is mild, while it becomes severe for the complex Langevin dynamics.

We perform the first iterative Monte Carlo (IMC) analysis of fragmentation functions constrained by all available data from single-inclusive $e^{+}{e}^{-}$ annihilation into pions and kaons. The IMC method eliminates potential bias in traditional analyses based on single fits introduced by fixing parameters not well constrained by the data and provides a statistically rigorous determination of uncertainties. Our analysis reveals specific features of fragmentation functions using the new IMC methodology and those obtained from previous analyses, especially for light quarks and for strange quark fragmentation to kaons.

We provide analytical results for the $O({\alpha }_s)$ corrections to the double-spin density matrix elements in the reaction $e^{+}{e}^{-}\to t\overline{t}$. These concern the elements $ll$, $lt$, $ln$, $tt$, $tn$, and $nn$ of the double-spin density matrix elements where $l$, $t$, $n$ stand for longitudinal, transverse and normal orientations with respect to the beam frame spanned by the electron and the top quark momentum.

The decuplet baryons, $\mathrm{\Delta }$, ${\mathrm{\Sigma }}^{*}$, ${\mathrm{\Xi }}^{*}$, and ${\mathrm{\Omega }}^{-}$, are studied in nuclear matter by using the in-medium QCD sum rules. By fixing the three-momentum of the particles under consideration at the rest frame of the medium, the negative energy contributions are removed. It is obtained that the parameters of the $\mathrm{\Delta }$ baryon are more affected by the medium against the ${\mathrm{\Omega }}^{-}$ state, containing three strange quarks, whose mass and residue are not considerably affected by the medium. We also find the vector and scalar self-energies of these baryons in nuclear matter. By the recent progresses at the $\overline{P}\mathrm{ANDA}$ experiment at the FAIR and NICA facility, it may be possible to study the in-medium properties of such states, even the multistrange ${\mathrm{\Xi }}^{*}$ and ${\mathrm{\Omega }}^{-}$ systems, in the near future.

The presence of a zero texture in the neutrino mass matrix can indicate the presence of an underlying symmetry which can generate neutrino mass and mixing. In this paper, for the first time, we study the four-zero textures of the low energy neutrino mass matrix in the presence of an extra light-sterile neutrino, i.e., the $3+1$ neutrino scheme. In our analysis, we find that out of the 210 possible four-zero textures only 15 textures are allowed. We divide the allowed four-zero textures into two classes—$A$ in which the value of mass matrix element $M_{ee}$ is zero and class $B$ in which $M_{ee}$ is nonzero. In this way, we obtain ten possible four-zero textures in class $A$ and five possible four-zero textures in class $B$. In our analysis, we find that for normal hierarchy the allowed number of textures in class $A$ ($B$) is nine (three). For the case of inverted hierarchy, we find that two textures in class $A$ are disallowed, and these textures are different from the disallowed textures for normal hierarchy in class $A$. However, we find that all the five textures in class $B$ are allowed for the inverted hierarchy. Based on analytic expressions for the elements $M_{\alpha \beta }$, we discuss the reasons for certain textures being disallowed. We also discuss the correlations between the different parameters of the allowed textures. Finally, we present the implications of our study on experimental searches for neutrinoless double beta decay.

Classification of jets as originating from light-flavor or heavy-flavor quarks is an important task for inferring the nature of particles produced in high-energy collisions. The large and variable dimensionality of the data provided by the tracking detectors makes this task difficult. The current state-of-the-art tools require expert data reduction to convert the data into a fixed low-dimensional form that can be effectively managed by shallow classifiers. We study the application of deep networks to this task, attempting classification at several levels of data, starting from a raw list of tracks. We find that the highest-level lowest-dimensionality expert information sacrifices information needed for classification, that the performance of current state-of-the-art taggers can be matched or slightly exceeded by deep-network-based taggers using only track and vertex information, that classification using only lowest-level highest-dimensionality tracking information remains a difficult task for deep networks, and that adding lower-level track and vertex information to the classifiers provides a significant boost in performance compared to the state of the art.

We use gauge or string duality to estimate the Debye screening mass at nonzero temperature and baryon chemical potential. We interpret this mass as the smallest one in the open string channel. Comparisons are made with the results from holography and lattice QCD.

We study the universal conditions for quantum nonperturbative stability against bubble nucleation for pertubatively stable AdS vacua based on positive energy theorems. We also compare our analysis with the preexisting ones in the literature carried out within the thin-wall approximation. The aforementioned criterion is then tested in two explicit examples describing massive type IIA string theory compactified on $S^3$ and $S^3\times S^3$, respectively. The AdS landscape of both classes of compactifications is known to consist of a set of isolated points. The main result is that all critical points respecting the Breitenlohner-Freedman (BF) bound also turn out be stable at a nonperturbative level. Finally, we speculate on the possible universal features that may be extracted from the above specific examples.

We use the intertwining properties of integral transformations to provide a compact proof of the holographic equivalence between the first law of entanglement entropy and the linearized gravitational equations in the context of the $\mathrm{AdS}/\mathrm{CFT}$ correspondence. We build upon the framework developed by Faulkner et al. using the Wald formalism and exploit the symmetries of the vacuum modular Hamiltonian of ball-shaped boundary regions.

We study a generalization of the loosely bound Skyrme model which consists of the Skyrme model with a sixth-order derivative term—motivated by its fluidlike properties—and the second-order loosely bound potential—motivated by lowering the classical binding energies of higher-charged Skyrmions. We use the rational map approximation for the Skyrmion of topological charge $B=4$, calculate the binding energy of the latter, and estimate the systematic error in using this approximation. In the parameter space that we can explore within the rational map approximation, we find classical binding energies as low as 1.8%, and once taking into account the contribution from spin-isospin quantization, we obtain binding energies as low as 5.3%. We also calculate the contribution from the sixth-order derivative term to the electric charge density and axial coupling.

In Molnár et al. Phys. Rev. D 93, 114025 (2016) the equations of anisotropic dissipative fluid dynamics were obtained from the moments of the Boltzmann equation based on an expansion around an arbitrary anisotropic single-particle distribution function. In this paper we make a particular choice for this distribution function and consider the boost-invariant expansion of a fluid in one dimension. In order to close the conservation equations, we need to choose an additional moment of the Boltzmann equation. We discuss the influence of the choice of this moment on the time evolution of fluid-dynamical variables and identify the moment that provides the best match of anisotropic fluid dynamics to the solution of the Boltzmann equation in the relaxation-time approximation.

We study an interesting relevant deformation of the simplest interacting $\mathcal{N}=2$ superconformal field theory (SCFT)—the original Argyres-Douglas (AD) theory. We argue that, although this deformation is not strictly speaking Banks-Zaks–like (certain operator dimensions change macroscopically), there are senses in which it constitutes a mild deformation of the parent AD theory: the exact change in the $a$ anomaly is small and is essentially saturated at one loop. Moreover, contributions from IR operators that have a simple description in the UV theory reproduce a particular limit of the IR index to a remarkably high order. These results lead us to conclude that the IR theory is an interacting $\mathcal{N}=1$ SCFT with particularly small $a$ and $c$ central charges and that this theory sheds some interesting light on the spectrum of its AD parent. Our results also lead us to the conclusion that the theory spaces emanating from some of the simplest $\mathcal{N}=1$ gauge theories may be richer than anticipated.

We calculate the quark self-energy in a quark-gluon plasma that possesses an ellipsoidal momentum-space anisotropy in the local rest frame. By introducing additional transverse-momentum anisotropy parameters into the parton distribution functions, we generalize previous results which were obtained for the case of a spheroidal anisotropy. Our results demonstrate that the presence of anisotropies in the transverse directions affects the real and imaginary parts of quark self-energy and, consequently, the self-energy depends on both the polar and azimuthal angles in the local rest frame of the matter. Our results for the quark self-energy set the stage for the calculation of the effects of ellipsoidal momentum-space anisotropy on quark-gluon plasma photon spectra and collective flow.

We derive the complete set of geodesic equations for massive and massless test particles of a five-dimensional, charged, rotating black hole solution of the Einstein-Maxwell-Chern-Simons field equations in five-dimensional minimal gauged supergravity and present their analytical solutions in terms of Weierstrass elliptic functions. We study the polar and radial motion, depending on the black hole and test particle parameters, and characterize the test particle motion qualitatively by means of effective potentials. We use the analytical solutions in order to visualize the test particle motion by two- and three-dimensional plots.

Observations of gravitational lenses in strong gravitational fields give us a clue to understanding dark compact objects. In this paper, we extend a method to obtain a deflection angle in a strong deflection limit provided by Bozza [Phys. Rev. D 66, 103001 (2002)] to apply to ultrastatic spacetimes. We also discuss on the order of an error term in the deflection angle. Using the improved method, we consider gravitational lensing by an Ellis wormhole, which is an ultrastatic wormhole of the Morris-Thorne class.