We evaluate the second and fourth order quark number susceptibilities in hot QCD using two variations of resummed perturbation theory. On one hand, we carry out a one-loop calculation within hard-thermal-loop perturbation theory, and on the other hand perform a resummation of the four-loop finite density equation of state derived using a dimensionally reduced effective theory. Our results are subsequently compared with recent high precision lattice data, and their agreement thoroughly analyzed.

A search for resonances decaying to top quark-antiquark pairs is performed using a $\mathrm{\text{dilepton}}+\mathrm{\text{jets}}$ data sample recorded by the CMS experiment at the LHC in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ corresponding to an integrated luminosity of $5.0{\mathrm{fb}}^{-1}$. No significant deviations from the standard model background are observed. Upper limits are presented for the production cross section times branching fraction of top quark-antiquark resonances for masses from 750 to 3000 GeV. In particular, the existence of a leptophobic topcolor particle $Z^{\prime }$ is excluded at the 95% confidence level for resonance masses $M_{Z^{\prime }}<1.3\mathrm{TeV}$ for ${\Gamma }_{Z^{\prime }}=0.012M_{Z^{\prime }}$, and $M<1.9\mathrm{TeV}$ for ${\Gamma }_{Z^{\prime }}=0.10M_{Z^{\prime }}$.

In the Einstein gravity, it is well known that strictly stationary and vacuum regular spacetime should be the Minkowski spacetime. In the Einstein-Gauss-Bonnet theory, we shall show that strictly static (no event horizon), vacuum, and asymptotically flat spacetimes with conformally static slices are the Minkowski spacetime when the curvature corrections are small.

We prove explicitly that the general $D=3$, $\mathcal{N}=4$ Chern-Simons-matter theory has a complete $OSp(4|4)$ superconformal symmetry and construct the corresponding conserved currents. We rederive the $OSp(5|4)$ superconformal currents in the general $\mathcal{N}=5$ theory as special cases of the $OSp(4|4)$ currents by enhancing the supersymmetry from $\mathcal{N}=4$ to $\mathcal{N}=5$. The closure of the full $OSp(4|4)$ superconformal algebra is verified explicitly.

Low-energy effective field theory describing a nonrelativistic three-body system is analyzed in the Wilsonian renormalization group method. No effective auxiliary field (dimeron) that corresponds to two-body propagation is introduced. The Efimov effect is expected in the case of an infinite two-body scattering length and is believed to be related to the limit cycle behavior in the three-body renormalization group equations (RGEs). If the one-loop property of the RGEs for the nonrelativistic system without the dimeron field, which is essential in deriving RGEs in the two-body sector, persists in the three-body sector, it appears to prevent the emergence of limit cycle behavior. We explain how the multiloop diagrams contribute in the three-body sector without contradicting the one-loop property of the RGEs and derive the correct RGEs, which lead to the limit cycle behavior. The Efimov parameter, $s_0$, is obtained within a few percent error in the leading orders. We also remark on the correct use of the dimeron formulation. We find rich renormalization group flow structure in the three-body sector. In particular, a novel nontrivial fixed point of the three-body couplings is found when the two-body interactions are absent. We also find, on the two-body nontrivial fixed point, the limit cycle is realized as a loop of finite size in the space of three-body coupling constants when terms with derivatives are included.

Supersymmetric field theories possess a rich structure in their supercurrent supermultiplets. Some symmetries are manifest in one supercurrent supermultiplet but not in the others; for instance, $R$ symmetry is manifest in the $R$ multiplet but not in the Ferrara-Zumino multiplet. Similarly, we argue that dilatation symmetry is manifest in the virial multiplet (also known as a variant minimal supercurrent supermultiplet in the literature). It reveals that $R$ symmetry and dilatation symmetry are conceptually independent without further assumptions even though the superconformal symmetry connects the two. We show the structure of the virial multiplet for general renormalizable supersymmetric field theories in ($1+3$) dimensions to all orders in perturbation theory, and discuss the condition for the dilatation invariance (but not necessarily $R$ symmetric nor superconformal). We present novel scale invariant trajectories with a nilpotent structure in coupling constants for nonunitary Wess-Zumino models with nonvanishing beta functions, which are, therefore, not superconformal.

The duality angles deformation developed by de Roo and Wagemans within the context of $N=4$ gauged supergravity is used in order to study certain classes of gaugings of $N=8$ supergravity, namely, those that are consistent when halving the maximal $D=4$ theory. After reviewing the truncation process from $N=8$ to $N=4$ supergravity in terms of the embedding tensor formalism, the de Roo-Wagemans phases method is implemented for solving the resulting constraints on the gauging parameters by means of the Schön-Weidner ansatz. In contrast with the twenty semisimple $N=4$ gaugings admitting more than a single $SL(2)$ angle deforming their decompositions reported in the literature, it is proven that only three of them can be embedded back into the $N=8$ theory. The scalar potential derived for only two of these gauge groups exhibits an extremum in the origin of the scalar manifold. These extrema are not stable under fluctuations of all the scalar fields.

Gravitational waves at suitable frequencies can resonantly interact with a binary system, inducing changes to its orbit. A stochastic gravitational wave background causes the orbital elements of the binary to execute a classic random walk, with the variance of orbital elements growing with time. The lack of such a random walk in binaries that have been monitored with high precision over long time scales can thus be used to place an upper bound on the gravitational wave background. Using periastron time data from the Hulse-Taylor binary pulsar spanning $\sim 30$ years, we obtain a bound of $h_{\mathrm{c}}<7.9\times {10}^{-14}$ at $\sim {10}^{-4}\mathrm{Hz}$, where $h_{\mathrm{c}}$ is the strain amplitude per logarithmic frequency interval. Our constraint complements those from pulsar timing arrays, which probe much lower frequencies, and ground-based gravitational wave observations, which probe much higher frequencies. Interesting sources in our frequency band, which overlaps the lower sensitive frequencies of proposed space-based observatories, include white dwarf/supermassive black hole binaries in the early/late stages of inspiral, and TeV-scale preheating or phase transitions. The bound improves as $(\mathrm{\text{time span}}{)}^{-2}$ and $(\mathrm{\text{sampling rate}}{)}^{-1/2}$. The Hulse-Taylor constraint can be improved to $\sim 3.8\times {10}^{-15}$ with a suitable observational campaign over the next decade. Our approach can also be applied to other binaries, including (with suitable care) the Earth-Moon system, to obtain constraints at different frequencies. The observation of additional binary pulsars with the Square Kilometer Array could reach a sensitivity of $h_{\mathrm{c}}\sim 3\times {10}^{-17}$.

The inspiral and merger of black hole binary systems are a promising source of gravitational waves for the array of advanced interferometric ground-based gravitational-wave detectors currently being commissioned. The most effective method to look for a signal with a well understood waveform, such as the binary black hole signal, is matched filtering against a library of model waveforms. While current model waveforms are comprised solely of the dominant radiation mode, the quadrupole mode, it is known that there can be significant power in the higher-order modes for a broad range of physically relevant source parameters during the merger of the black holes. The binary black hole waveforms produced by numerical relativity are accurate through late inspiral, merger, and ringdown and include the higher-order modes. The available numerical-relativity waveforms span an increasing portion of the physical parameter space of unequal mass, spin and precession. In this paper, we investigate the degree to which gravitational-wave searches could be improved by the inclusion of higher modes in the model waveforms, for signals with a variety of initial mass ratios and generic spins. Our investigation studies how well the quadrupole-only waveform model matches the signal as a function of the inclination and orientation of the source and how the modes contribute to the distance reach into the Universe of Advanced LIGO for a fixed set of internal source parameters. The mismatch between signals and quadrupole-only waveforms can be large, dropping below 0.97 for up to 65% of the source sky for the nonprecessing cases we studied, and over a larger area in one precessing case. There is a corresponding 30% increase in detection volume that could be achieved by adding higher modes to the search; however, this is mitigated by the fact that the mismatch is largest for signals which radiate the least energy and to which the search is therefore least sensitive. Likewise, the mismatch is largest in the directions from the source along which the least energy is radiated.

It has recently been suggested that black holes may be described as condensates of weakly interacting gravitons at a critical point, exhibiting strong quantum effects. In this paper, we study a model system of attractive bosons in one spatial dimension which is known to undergo a quantum phase transition. We demonstrate explicitly that indeed quantum effects are important at the critical point, even if the number of particles is macroscopic. Most prominently, we evaluate the entropy of entanglement between different momentum modes and observe it to become maximal at the critical point. Furthermore, we explicitly see that the leading entanglement is between long-wavelength modes and is hence a feature independent of ultraviolet physics. If applicable to black holes, our findings substantiate the conjectured breakdown of semiclassical physics even for large black holes. This can resolve long-standing mysteries, such as the information paradox and the no-hair theorem.

Black-hole–neutron-star mergers resulting in the disruption of the neutron star and the formation of an accretion disk and/or the ejection of unbound material are prime candidates for the joint detection of gravitational-wave and electromagnetic signals when the next generation of gravitational-wave detectors comes online. However, the disruption of the neutron star and the properties of the postmerger remnant are very sensitive to the parameters of the binary (mass ratio, black-hole spin, neutron star radius). In this paper, we study the impact of the radius of the neutron star and the alignment of the black-hole spin on black-hole–neutron-star mergers within the range of mass ratio currently deemed most likely for field binaries ($M_{\mathrm{BH}}\sim 7M_{\mathrm{NS}}$) and for black-hole spins large enough for the neutron star to disrupt ($J_{\mathrm{BH}}/M_{\mathrm{BH}}^2=0.9$). We find that (i) In this regime, the merger is particularly sensitive to the radius of the neutron star, with remnant masses varying from $0.3M_{\mathrm{NS}}$ to $0.1M_{\mathrm{NS}}$ for changes of only 2 km in the NS radius; (ii) $0.01M_{\odot }–0.05M_{\odot }$ of unbound material can be ejected with kinetic energy $\gtrsim {10}^{51}\mathrm{ergs}$, a significant increase compared to low mass ratio, low spin binaries. This ejecta could power detectable postmerger optical and radio afterglows. (iii) Only a small fraction of the Advanced LIGO events in this parameter range have gravitational-wave signals which could offer constraints on the equation of state of the neutron star (at best $\sim 3\%$ of the events for a single detector at design sensitivity). (iv) A misaligned black-hole spin works against disk formation, with less neutron-star material remaining outside of the black hole after merger, and a larger fraction of that material remaining in the tidal tail instead of the forming accretion disk. (v) Large kicks $v_{\mathrm{kick}}\gtrsim 300\mathrm{km}/\mathrm{s}$ can be given to the final black hole as a result of a precessing black-hole–neutron-star merger, when the disruption of the neutron star occurs just outside or within the innermost stable spherical orbit.

The discovery of the accelerated expansion of the Universe has had a vast resonance on a number of physical disciplines. In recent years several viable modified gravity models have been proposed, which naturally lead to a late-time de Sitter stage while basically reducing to General Relativity in the early Universe. We consider a contracting cloud of pressureless dust, having arbitrary mass and initial density, and study some aspects of these modified gravity models. We show how the increasing energy/mass density may lead to a curvature singularity and discuss the typical time scales for its development.

Optimal extraction of information from gravitational-wave observations of binary black-hole coalescences requires detailed knowledge of the waveforms. Current approaches for representing waveform information are based on spin-weighted spherical harmonic decomposition. Higher-order harmonic modes carrying a few percent of the total power output near merger can supply information critical to determining intrinsic and extrinsic parameters of the binary. One obstacle to constructing a full multimode template of merger waveforms is the apparently complicated behavior of some of these modes; instead of settling down to a simple quasinormal frequency with decaying amplitude, some $|m|\ne \ell$ modes show periodic bumps characteristic of mode mixing. We analyze the strongest of these modes—the anomalous (3, 2) harmonic mode—measured in a set of binary black-hole merger waveform simulations, and show that to leading order, they are due to a mismatch between the spherical harmonic basis used for extraction in 3D numerical relativity simulations, and the spheroidal harmonics adapted to the perturbation theory of Kerr black holes. Other causes of mode mixing arising from gauge ambiguities and physical properties of the quasinormal ringdown modes are also considered and found to be small for the waveforms studied here.

The fermionic condensate and vacuum expectation value of the energy-momentum tensor, for a massive fermionic field on the background of anti–de Sitter (AdS) spacetime, in the geometry of two parallel boundaries with bag boundary conditions, are investigated. Vacuum expectation values, expressed as a series involving the eigenvalues of the radial quantum number, are neatly decomposed into boundary-free, single-boundary-induced, and second-boundary-induced parts, with the help of the generalized Abel-Plana summation formula. In this way, the renormalization procedure is very conveniently reduced to the one corresponding to boundary-free AdS spacetime. The boundary-induced contributions to the fermionic condensate and to the vacuum expectation value of the energy density are proven to be everywhere negative. The vacuum expectation values are exponentially suppressed at distances from the boundaries much larger than the curvature radius of the AdS space. Near the boundaries, effects related to the curvature of the background spacetime are shown to be subdominant and, to leading order, all known results for boundaries in the Minkowski bulk are recovered. Zeta function techniques are successfully used for the evaluation of the total vacuum energy in the region between the boundaries. It is proven that the resulting interaction forces between them are attractive and that, for large separations, they also decay exponentially. Finally, our results are extended and explicitly translated to fermionic Casimir densities in braneworld scenarios of Randall-Sundrum type.

Any unified dark matter cosmology can be decomposed into dark matter interacting with vacuum energy, without introducing any additional degrees of freedom. We present observational constraints on an interacting vacuum plus dark energy corresponding to a generalized Chaplygin gas cosmology. We consider two distinct models for the interaction leading to either a barotropic equation of state or dark matter that follows geodesics, corresponding to a rest-frame sound speed equal to the adiabatic sound speed or zero sound speed, respectively. For the barotropic model, the most stringent constraint on $\alpha$ comes from the combination of $\mathrm{CMB}+\mathrm{SNIa}+\mathrm{LSS}(\mathrm{m})$ gives $\alpha <5.66\times {10}^{-6}$ at the 95% confidence level, which indicates that the barotropic model must be extremely close to the $\Lambda \mathrm{CDM}$ cosmology. For the case where the dark matter follows geodesics, perturbations have zero sound speed, and $\mathrm{CMB}+\mathrm{SNIa}+\mathrm{gISW}$ then gives the much weaker constraint $-0.15<\alpha <0.26$ at the 95% confidence level.

Future space-based gravity wave (GW) experiments such as the Big Bang Observatory (BBO), with their excellent projected, one sigma angular resolution, will measure the luminosity distance to a large number of GW sources to high precision, and the redshift of the single galaxies in the narrow solid angles towards the sources will provide the redshifts of the gravity wave sources. One sigma BBO beams contain the actual source in only 68% of the cases; the beams that do not contain the source may contain a spurious single galaxy, leading to misidentification. To increase the probability of the source falling within the beam, larger beams have to be considered, decreasing the chances of finding single galaxies in the beams. Saini et al. [T. D. Saini, S. K. Sethi, and V. Sahni, Phys. Rev. D 81, 103009 (2010)] argued, largely analytically, that identifying even a small number of GW source galaxies furnishes a rough distance-redshift relation, which could be used to further resolve sources that have multiple objects in the angular beam. In this work we further develop this idea by introducing a self-calibrating iterative scheme which works in conjunction with Monte Carlo simulations to determine the luminosity distance to GW sources with progressively greater accuracy. This iterative scheme allows one to determine the equation of state of dark energy to within an accuracy of a few percent for a gravity wave experiment possessing a beam width an order of magnitude larger than BBO (and therefore having a far poorer angular resolution). This is achieved with no prior information about the nature of dark energy from other data sets such as type Ia supernovae, baryon acoustic oscillations, cosmic microwave background, etc.

We analyze the Brownian thermal noise of a multilayer dielectric coating used in high-precision optical measurements, including interferometric gravitational-wave detectors. We assume the coating material to be isotropic, and therefore study thermal noises arising from shear and bulk losses of the coating materials. We show that coating noise arises not only from layer thickness fluctuations, but also from fluctuations of the interface between the coating and substrate, driven by fluctuating shear stresses of the coating. Although thickness fluctuations of different layers are statistically independent, there exists a finite coherence between the layers and the substrate-coating interface. In addition, photoelastic coefficients of the thin layers (so far not accurately measured) further influence the thermal noise, although at a relatively low level. Taking into account uncertainties in material parameters, we show that significant uncertainties still exist in estimating coating Brownian noise.

The thermal relaxation time (${\tau }_{{\kappa }_{\mathrm{ee}}}$) for the degenerate electron plasma has been calculated by incorporating non-Fermi liquid corrections both for the thermal conductivity and specific heat capacity. Perturbative results are presented by making expansion in $T/m_D$ with next to leading order corrections. We see that the next to leading order non-Fermi liquid corrections further reduce the decrease in relaxation time due to the leading order corrections.

We enumerate the simplest models that have baryon number violation at the classical level but do not give rise to proton decay. These models have scalar fields in two representations of $SU(3)\times SU(2)\times U(1)$ and violate baryon number by two units. Some of the models give rise to $n\overline{n}$ (neutron-antineutron) oscillations, while some also violate lepton number by two units. We discuss the range of scalar masses for which $n\overline{n}$ oscillations are measurable in the next generation of experiments. We give a brief overview of the phenomenology of these models and then focus on one of them for a more quantitative discussion of $n\overline{n}$ oscillations, the generation of the cosmological baryon number, the electric dipole moment of the neutron, and $K^0\mathrm{\text{−}}{\overline{K}}^0$ mixing.

In the presence of even minuscule baryonic $R$-parity violation (RPV), the stop can be the lightest superpartner and evade LHC searches because it decays into two jets. In order to cover this interesting possibility, we here consider new searches for RPV stops produced in gluino cascades. While typical searches for gluinos decaying to stops rely on same-sign dileptons, the RPV cascades usually have fewer hard leptons, less excess missing energy, and more jets than $R$-parity conserving cascades. If the gluino is a Dirac fermion, same-sign dilepton signals are also often highly depleted. We therefore explore search strategies that use single-lepton channels, and combat backgrounds using $H_T$, jet counting, and more detailed multijet kinematics or jet substructure. We demonstrate that the stop mass peaks can be fully reconstructed over a broad range of spectra, even given the very high jet multiplicities. This would not only serve as a “double-discovery” opportunity, but would also be a spectacular confirmation that the elusive top partner has been hiding in multijets.