While the properties of the 125 GeV Higgs bosonlike particle observed by the ATLAS and CMS collaborations are largely compatible with those predicted for the Standard Model state, significant deviations are present in some cases. We, therefore, test the viability of a beyond the Standard Model scenario based on supersymmetry, the $CP$-violating next-to-minimal supersymmetric Standard Model, against the corresponding experimental observations. Namely, we identify possible model configurations in which one of its Higgs bosons is consistent with the LHC observation and evaluate the role of the explicit complex phases on both the mass and diphoton decay of such a Higgs boson. Through a detailed analysis of some benchmark points corresponding to each of these configurations, we highlight the impact of the $CP$-violating phases on the model predictions compared to the $CP$-conserving case.

We show that mass measurements for new particles appearing in decay chains can be improved by determining the boundary of the available phase space in its full dimensionality rather than by using one-dimensional kinematic features for each stage of the cascade decay. This is demonstrated for the case of one particle decaying to three visible and one invisible particles in a two-stage cascade, but our methods also apply to a more general set of decay topologies. We show that not only mass differences but also the overall scale of masses can be determined with high precision without having to rely on cross section information. The improvement arises from the properties of the higher-dimensional phase space itself, independent of the matrix element for the decay, and it is not weakened by the presence of intermediate on-shell particles in the cascade. Our results are particularly significant for the case of low signal statistics, a distinct possibility for new physics searches in the near future.

We analyze the Euclidean version of supersymmetric quantum mechanics on the lattice by means of a numerical path integral. We consider two different lattice derivatives and improve the actions containing them with respect to supersymmetry by systematically adding interaction terms with nonzero extent. To quantize this improvement, we measure boson and fermion masses and Ward identities for the naive as well as the improved models. The masses are degenerate in all models, but the magnitude of the Ward identities decreases significantly for both derivative operators using the improved actions. This is a clear sign that the breaking of supersymmetry due to lattice artifacts is reduced.

We present the calculation of the $\mathcal{O}({\alpha }_s^2{C}_F{T}_F)$ massive quark corrections to the soft function for the double hemisphere jet mass distribution in $e^{+}{e}^{-}$ collisions, a necessary ingredient for the calculation of several event shape distributions at ${\mathrm{N}}^3\mathrm{LL}$ order. The use of the mass as an infrared regulator allows us to derive the momentum space results for the massless quark structures at $\mathcal{O}({\alpha }_s^2{C}_F{T}_F{n}_f)$ and the gluonic structures at $\mathcal{O}({\alpha }_s^2{C}_A{C}_F)$, which have not been given so far in the literature. Furthermore, we compute the corresponding corrections in the soft function for thrust, the most prominent projection of the double hemisphere mass distribution. Finally we give expressions for the corresponding renormalon subtractions in the gap scheme.

The amplitude of double Higgs boson production by the gluon fusion, $gg\to hh$, is known to be small due to cancellation between the graphs with the boson trilinear coupling and those with the coupling to the top quark. For this reason a study of this process was suggested as a sensitive probe of the Higgs sector nonlinearity. We calculate in a closed analytical form this amplitude at the threshold of the two bosons, where the cancellation is the strongest, and discuss the origin of the small value of the amplitude. We also note that the cancellation in the double boson production is in fact a part of a more general phenomenon of suppression of similar threshold amplitudes for multiple scalar boson production, which, although not directly relevant to the actual top quark and the Higgs boson, can be useful in other studies.

In this work we determine the power spectrum of the gravitational potential of the primordial fluctuations for an inflationary model whose inflaton is a noncanonical scalar field of the tachyon-type. The respective background field equations for an inverse-square potential produce a power-law inflation, and it is explicitly shown that for such a potential the power spectrum tends to be scale independent for highly accelerated regimes in the inflationary expansion.

We implement D7 flavor branes in anti-de Sitter-sliced coordinates on ${\mathrm{AdS}}_5\times S^5$ with the ansatz that the brane fluctuates only in the warped ($\mu$) direction in this slicing, which is particularly appropriate for studying the Janus solution. The natural field theory dual in this slicing is $\mathcal{N}=4$ super-Yang–Mills on two copies of ${\mathrm{AdS}}_4$. Branes extending from $\mu =\pm \pi /2$ can end at different locations, giving rise to quarks with a piecewise constant mass on each ${\mathrm{AdS}}_4$ half-space, jumping discontinuously between them. A second class of flavor brane solutions exists in this coordinate system, dubbed “continuous” flavor branes, which extend across the entire range of $\mu$. We propose that the correct dual interpretation of the “disconnected” flavor brane in this ansatz is a quark hypermultiplet with constant mass on one of the ${\mathrm{AdS}}_4$ half-spaces with totally reflecting boundary conditions at the boundary of ${\mathrm{AdS}}_4$; whereas the dual interpretation of a continuous flavor brane has totally transparent boundary conditions. Numerical studies indicate that AdS-sliced D7 flavor branes of both classes exhibit spontaneous chiral symmetry breaking, as a nonzero vacuum expectation value persists for solutions of the equation of motion down to zero mass. Continuous flavor branes in this ansatz exhibit many other surprising behaviors: their masses seem to be capped at a modest value near $m=0.551$ in units of the inverse AdS radius, and there may be a phase transition between continuous branes of different configurations. We also numerically study quark states in Janus. The behavior of the mass and vacuum expectation value is similar in Janus, including the existence of chiral symmetry breaking at zero mass, though qualitative features of the phase diagram change (sometimes significantly) as the Janus parameter $c_0$ increases.

We compute the elliptic flow $v_2$ of thermal photons in a strongly coupled plasma with constant magnetic field via gauge/gravity duality. The D3/D7 embedding is applied to generate the contributions from massive quarks. By considering the cases in $2+1$ flavor super Yang-Mills analogous to the photon production in quark gluon plasma, we obtain the thermal photon $v_2$, which is qualitatively consistent with the direct photon $v_2$ measured at the relativistic heavy ion collider at intermediate energy. However, due to the simplified setup, the thermal photon $v_2$ in our model should be regarded as the upper bound for the $v_2$ generated by solely a magnetic field in the strongly coupled scenario.

We discuss the description of the baryon as a dyonic instanton in holographic QCD. The solution generalizes the Skyrmion, taking into account the infinite tower of vector and axial mesons as well as the chiral condensate. We construct a solution with unit baryon charge and study the dependence of its mass on the chiral condensate. An elegant explanation of the Ioffe formula is found, and we speculate on the relation between the physical scales of the chiral and conformal symmetry breaking.

In three dimensions, the pure Maxwell theory with a compact $U(1)$ gauge group is dual to a free compact scalar, and it flows from the Maxwell theory with a noncompact gauge group in the ultraviolet to a noncompact free massless scalar theory in the infrared. We compute the vacuum disk entanglement entropy all along this flow and show that the renormalized entropy $F(r)$ decreases monotonically with the radius $r$ as predicted by the F-theorem, interpolating between a logarithmic growth for small $r$ (matching the behavior of the $S^3$ free energy) and a constant at large $r$ (equal to the free energy of the conformal scalar). The calculation is carried out by the replica trick, employing the scalar formulation of the theory. The Rényi entropies for $n>1$ are given by a sum over winding sectors, leading to a Riemann-Siegel theta function. The extrapolation to $n=1$, to obtain the von Neumann entropy, is done by analytic continuation in the large- and small-$r$ limits and by a numerical extrapolation method at intermediate values. We also compute the leading contribution to the renormalized entanglement entropy of the compact free scalar in higher dimensions. Finally, we point out some interesting features of the reduced density matrix for the compact scalar, and its relation to that for the noncompact theory.

We show that the canonical oscillation-based (nonresonant) production of sterile neutrino dark matter is inconsistent at $>99\%$ confidence with observations of galaxies in the Local Group. We set lower limits on the nonresonant sterile neutrino mass of 2.5 keV (equivalent to 0.7 keV thermal mass) using phase-space densities derived for dwarf satellite galaxies of the Milky Way as well as limits of 8.8 keV (equivalent to 1.8 keV thermal mass) based on subhalo counts of $N$-body simulations of M 31 analogs. Combined with improved upper mass limits derived from significantly deeper x-ray data of M 31 with full consideration for background variations, we show that there remains little room for nonresonant production if sterile neutrinos are to explain 100% of the dark matter abundance. Resonant and nonoscillation sterile neutrino production remain viable mechanisms for generating sufficient dark matter sterile neutrinos.

We develop Coulomb gas pictures of strong and weak coupling regimes of supersymmetric Yang-Mills theory in five and four dimensions. By relating them to the matrix models that arise in Chern-Simons theory, we compute their free energies in the large $N$ limit and establish relationships between the respective gauge theories. We use these correspondences to rederive the $N^3$ behavior of the perturbative free energy of supersymmetric gauge theory on certain toric Sasaki-Einstein five-manifolds, and the one-loop thermal free energy of $\mathcal{N}=4$ supersymmetric Yang-Mills theory on a spatial three-sphere.

Schwinger-Dyson equations are used to study the chiral phase diagram of QED in three dimensions. This computation is made with full frequency dependence in the two-point function gap equations for the first time. We also demonstrate that reliable results are attainable in spite of an infrared divergence that is endemic to the theory. A theoretically sound method for dealing with cutoff ultraviolet regulators is presented. Finally, it is shown that the quenched and instantaneous approximations often used in the literature are inaccurate.

A clock synchronization thought experiment is modeled by a diffeomorphism invariant “time delay” observable. In a sense, this observable probes the causal structure of the ambient Lorentzian spacetime. Thus, upon quantization, it is sensitive to the long expected smearing of the light cone by vacuum fluctuations in quantum gravity. After perturbative linearization, its mean and variance are computed in the Minkowski Fock vacuum of linearized gravity. The naïve divergence of the variance is meaningfully regularized by a length scale $\mu$, the physical detector resolution. This is the first time vacuum fluctuations have been fully taken into account in a similar calculation. Despite some drawbacks this calculation provides a useful template for the study of a large class of similar observables in quantum gravity. Due to their large volume, intermediate calculations were performed using computer algebra software. The resulting variance scales like ${(s{\ell }_p/\mu )}^2$, where ${\ell }_p$ is the Planck length and $s$ is the distance scale separating the (“lab” and “probe”) clocks. Additionally, the variance depends on the relative velocity of the lab and the probe, diverging for low velocities. This puzzling behavior may be due to an oversimplified detector resolution model or a neglected second-order term in the time delay.

We investigate rotating Einstein-Maxwell-dilaton (EMd) black holes in odd dimensions. Focusing on black holes with equal-magnitude angular momenta, we determine the domain of existence of these black holes. Nonextremal black holes reside with the boundaries determined by the static and the extremal rotating black holes. The extremal EMd black holes show proportionality of their horizon area and their angular momenta. Thus the charge does not enter. We also address the Einstein-Maxwell case, where the extremal rotating black holes exhibit two branches. On the branch emerging from the Myers-Perry solutions, their angular momenta are proportional to their horizon area, whereas on the branch emerging from the static solutions their angular momenta are proportional to their horizon angular momenta. Only subsets of the near-horizon solutions are realized globally. Investigating the physical properties of these EMd black holes, we note that one can learn much about the extremal rotating solutions from the much simpler static solutions. The angular momenta of the extremal black holes are proportional to the area of the static ones for the Kaluza-Klein value of the dilaton coupling constant, and remain analogous for other values. The same is found for the horizon angular velocities of the extremal black holes, which possess an analogous behavior to the surface gravity of the static black holes. The gyromagnetic ratio is rather well approximated by the “static” value, obtained perturbatively for small angular momenta.

We discuss the cosmological constant problem, at the minisuperspace level, within the framework of the so-called normalized general relativity. We prove that the Universe cannot be closed, and reassure that the accompanying cosmological constant $\mathrm{\Lambda }$ generically vanishes, at least classically. The theory does allow, however, for a special class of $\mathrm{\Lambda }\ne 0$ solutions which are associated with static closed Einstein universe and with Eddington-Lemaître universe.

We “derive” the Bekenstein-Hawking entropy for black holes based on the near-horizon symmetries of black hole space-times. To find out these symmetries we make use of an $(R,T)$ plane close to a Killing horizon. We identify a set of vector fields that preserves this plane and forms a Witt algebra. The corresponding algebra of Hamiltonians is shown to have a nontrivial central extension. Using the Cardy formula and the central charge we obtain the Bekenstein-Hawking entropy.

Some theorems for a static prefect fluid sphere, i.e., a star, in the presence of a positive cosmological constant are proved. These theorems put bounds on the pressure profile and internal compactness of the star.