In the simplest inflationary model $V=\frac{1}{2}{m}^2{\varphi }^2$, we provide a prediction accurate up to 1% for the spectral index $n_s$ and the tensor-to-scalar ratio $r$ assuming instantaneous reheating and a standard thermal history: $n_s=0.9668\pm 0.0003$ and $r=0.131\pm 0.001$. This represents the simplest and most informative point in the $(n_s,r)$ plane. The result is independent of the details of reheating (or preheating) provided the conversion to radiation is sufficiently fast. A slower reheating or a modified postinflationary evolution (with an equation of state parameter $w\le 1/3$) pushes towards smaller $n_s$ (and larger $r$), so that our prediction corresponds to the maximum $n_s$ (and minimum $r$) for the quadratic potential. We also derive similar results for a general $V\propto {\varphi }^p$ potential.

Compact binary coalescences are a promising source of gravitational waves for second-generation interferometric gravitational-wave detectors. Although matched filtering is the optimal search method for well-modeled systems, alternative detection strategies can be used to guard against theoretical errors (e.g., involving new physics and/or assumptions about spin or eccentricity) while providing a measure of redundancy. In a previous paper, we showed how “seedless clustering” can be used to detect long-lived gravitational-wave transients in both targeted and all-sky searches. In this paper, we apply seedless clustering to the problem of low-mass ($M_{\text{total}}\le 10M_{\odot }$) compact binary coalescences for both spinning and eccentric systems. We show that seedless clustering provides a robust and computationally efficient method for detecting low-mass compact binaries.

If a primordial magnetic field in the Universe has nonzero helicity, the violation of parity symmetry results in nonzero correlations between cosmic microwave background temperature and B-mode polarization. In this paper we derive approximations to the relevant microwave background power spectra arising from a helical magnetic field. Using the cross-power spectrum between temperature and B-mode polarization from the WMAP nine-year data, we set a 95% confidence level upper limit on the helicity amplitude to be $10{\mathrm{nG}}^2\mathrm{Gpc}$ for helicity spectral index $n_H=-1.9$, for a cosmological magnetic field with effective field strength of 3 nG and a power-law index $n_B=-2.9$ near the scale-invariant value. Future microwave background polarization maps with greater sensitivity will be able to detect the helicity of an inflationary magnetic field well below the maximum value allowed by microwave background constraints on the magnetic field amplitude.

Although the cosmological paradigm based on cold dark matter and adiabatic, nearly scale-invariant primordial fluctuations is consistent with a wide variety of existing observations, it has yet to be sufficiently tested on scales smaller than those of massive galaxies, and various alternatives have been proposed that differ significantly in the consequent small-scale power spectrum (SSPS) of large-scale structure. Here we show that a powerful probe of the SSPS at $k\gtrsim 10{\mathrm{Mpc}}^{-1}$ can be provided by the 21 cm forest, that is, systems of narrow absorption lines due to intervening, cold neutral hydrogen in the spectra of high-redshift background radio sources in the cosmic reionization epoch. Such features are expected to be caused predominantly by collapsed gas in starless minihalos, whose mass function can be very sensitive to the SSPS. As specific examples, we consider the effects of neutrino mass, running spectral index (RSI) and warm dark matter (WDM) on the SSPS, and evaluate the expected distribution in optical depth of 21 cm absorbers out to different redshifts. Within the current constraints on quantities such as the sum of neutrino masses $\sum m_{\nu }$, running of the primordial spectral index $d{n}_s/d\ln k$ and WDM particle mass $m_{\mathrm{WDM}}$, the statistics of the 21 cm forest manifest observationally significant differences that become larger at higher redshifts. In particular, it may be possible to probe the range of $m_{\mathrm{WDM}}\gtrsim 10\mathrm{keV}$ that may otherwise be difficult to access. Future observations of the 21 cm forest by the Square Kilometer Array may offer a unique and valuable probe of the SSPS, as long as radio sources such as quasars or Population III gamma-ray bursts with sufficient brightness and number exist at redshifts of $z\gtrsim 10–20$, and the astrophysical effects of reionization and heating can be discriminated.

Coupling an antisymmetric tensor field to the electromagnetic field in a dyonic Reissner-Nordström-anti–de Sitter black hole background, we build a holographic model for the paramagnetism/ferromagnetism phase transition. In the case of zero magnetic field, the time reversal symmetry is broken spontaneously and spontaneous magnetization happens at low temperatures. The critical exponents are in agreement with the ones from mean field theory. In the case of nonzero magnetic field, the model realizes the hysteresis loop of a single magnetic domain and the magnetic susceptibility satisfies the Curie-Weiss law.

Supersymmetric theories with a $U(1{)}_R$ symmetry have Dirac gauginos, solve the supersymmetric flavor and $CP$ problems, and have distinctive collider signatures. However, when supergravity is included, the $U(1{)}_R$ must be broken, adding small Majorana mass terms which split the mass of the two components of the Dirac gaugino and lead to oscillations between $U(1{)}_R$ charge eigenstates. We present a general study of fermion-antifermion oscillations in this system, including the effects of decays and $CP$ violation. We consider the effects of such oscillations in the case where the two $U(1{)}_R$ charge eigenstates can decay into the same final state and show that $O(1)$ $CP$ violation is allowed. In the case of decays into final states containing leptons, such $CP$ violation can be observed as a same-sign dilepton asymmetry.

Recently, it has been argued that various measures of supersymmetric naturalness—electroweak, Higgs mass and EENZ/BG—when applied consistently, concur with one another and make very specific predictions for natural supersymmetric spectra. Highly natural spectra are characterized by light Higgsinos with mass not too far from $m_h$ and well-mixed but TeV-scale third generation squarks. We apply the unified naturalness measure to the case of heavy Higgs bosons $A$, $H$ and $H^{\pm }$. We find that their masses are bounded from above by naturalness depending on $\tan \beta$: e.g. for 10% fine-tuning and $\tan \beta \sim 10$, we expect $m_A\lesssim 2.5\mathrm{TeV}$ whilst for 3% fine-tuning and $\tan \beta$ as high as 50, then $m_A\lesssim 8\mathrm{TeV}$. Furthermore, the presence of light Higgsinos seriously alters the heavy Higgs boson branching ratios, thus diminishing prospects for usual searches into standard model final states, while new discovery possibilities arise due to the supersymmetric decay modes. The heavy supersymmetric decay modes tend to be $H,A,H^{\pm }\to W,Z$, or $h+{\cancel{E}}_T+\text{soft tracks}$ so that single heavy Higgs production is characterized by the presence of high $p_T$ $W$, $Z$ or $h$ bosons plus missing $E_T$. These new heavy Higgs boson signatures seem to be challenging to extract from SM backgrounds.

Fermionic top partners are a feature of many models of physics beyond the standard model. We propose a search strategy for single production of top partners focusing specifically on the dominant decay to $Wb$. The enormous background can be reduced by exploiting jet substructure to suppress top-pair production and by requiring a forward jet. This simple strategy is shown to produce a sensitive search for single top-partner production, in the context of composite Higgs models, that has competitive mass reach with existing experimental searches for top-partner-pair production at the 8 TeV LHC.

Lattice QCD simulations tend to become stuck in a single topological sector at fine lattice spacing or when using chirally symmetric overlap quarks. In such cases physical observables differ from their full QCD counterparts by finite volume corrections. These systematic errors need to be understood on a quantitative level and possibly removed. In this paper we extend an existing relation from the literature between two-point correlation functions at fixed and the corresponding hadron masses at unfixed topology by calculating all terms proportional to $1/V^2$ and $1/V^3$, where $V$ is the spacetime volume. Since parity is not a symmetry at fixed topology, parity mixing is comprehensively discussed. In the second part of this work we apply our equations to a simple model, quantum mechanics on a circle both for a free particle and for a square-well potential, where we demonstrate in detail, how to extract physically meaningful masses from computations or simulations at fixed topology.

The spectrum of excitations of triply charmed baryons is computed using lattice QCD including dynamical light quark fields. Calculations are performed on anisotropic lattices with temporal and spatial spacings $a_t=0.0351(2)\mathrm{fm}$ and $a_s\sim 0.12\mathrm{fm}$, respectively, and with pion mass of about 390 MeV. The spectrum obtained has baryonic states with well-defined total spin up to $\frac{7}{2}$ and the low-lying states closely resemble the expectation from models with an $SU(6)\times O(3)$ symmetry. Energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit, are computed and compared against data at other quark masses.

The lattice regularized Schwinger model with a so-called $\theta$ term is studied by using the Grassmann tensor renormalization group. We perform the Lee-Yang and Fisher zero analyses in order to investigate the phase structure at $\theta =\pi$. We find a first-order phase transition at larger fermion mass. Both the Lee-Yang zero and Fisher zero analyses indicate that the critical endpoint at which the first-order phase transition terminates belongs to the Ising universality class.

Based on homodyne detection, we discuss how the presence of an event horizon affects quantum communication between an inertial partner, Alice, and a uniformly accelerated partner, Rob. We show that there exists a low frequency cutoff for Rob’s homodyne detector that maximizes the signal to noise ratio and it approximately corresponds to the Unruh frequency. In addition, the low frequency cutoff which minimizes the conditional variance between Alice’s input state and Rob’s output state is also approximately equal to the Unruh frequency. Thus the Unruh frequency provides a natural low frequency cutoff in order to optimize quantum communication of both classical and quantum information between Alice and Rob.

We present a solution for rotating black holes in massive gravity. We first give a solution of massive gravity with one dynamical metric. Both metrics of this solution are expressed in the advanced Eddington-Finkelstein–like coordinates: the physical metric has the original Kerr line element, while the fiducial metric is flat, but written in a rotating Eddington-Finkelstein form. For the bigravity theory we give an analogue of this solution: the two metrics have the original Kerr form, but, in general, different black hole masses. The generalization of the solution to include the electric charge is also given; it is an analogue of the Kerr-Newman solution in general relativity. We also discuss further possible ways to generalize the solutions.

We propose a model of quantum gravity in arbitrary dimensions defined in terms of the Batalin Vilkovisky (BV) quantization of a supersymmetric, infinite dimensional matrix model. This gives an Alexandrov-Kontsevich-Schwarz-Zaboronsky (AKSZ)-type Chern-Simons theory with gauge algebra the space of observables of a quantum mechanical Hilbert space $\mathcal{H}$. The model is motivated by previous attempts to formulate gravity in terms of noncommutative, phase space, field theories as well as the Fefferman-Graham (FG) curved analog of Dirac spaces for conformally invariant wave equations. The field equations are flat connection conditions amounting to zero curvature and parallel conditions on operators acting on $\mathcal{H}$. This matrix-type model may give a better defined setting for a quantum gravity path integral. We demonstrate that its underlying physics is a summation over Hamiltonians labeled by a conformal class of metrics and thus a sum over causal structures. This gives in turn a model summing over fluctuating metrics plus a tower of additional modes—we speculate that these could yield improved UV behavior.

We provide an explicit expression for the renormalized expectation value of the stress-energy tensor of a spin-$1/2$ field in a spatially flat Friedmann-Lemaitre-Robertson-Walker universe. Its computation is based on the extension of the adiabatic regularization method to fermion fields introduced recently in the literature. The tensor is given in terms of UV-finite integrals in momentum space, which involve the mode functions that define the quantum state. As illustrative examples of the method efficiency, we see how to compute the renormalized energy density and pressure in two interesting cosmological scenarios: a de Sitter spacetime and a radiation-dominated universe. In the second case, we explicitly show that the late-time renormalized stress-energy tensor behaves as that of classical cold matter. We also check that, if we obtain the adiabatic expansion of the scalar field mode functions with a similar procedure to the one used for fermions, we recover the well-known WKB-type expansion.

We show that the generalized McVittie spacetime, which represents a black hole with time-dependent mass in an expanding universe, is an exact solution of a subclass of the Horndeski family of actions. The heat-flow term responsible for the energy transfer between the black hole and the cosmological background is generated by the higher-order kinetic gravity braiding term, which generalizes the cuscuton action that yields McVittie with constant mass as a solution. Finally, we show that this generalization can be understood in terms of a duality realized by a disformal transformation, connecting the cuscuton field theory to an extension of the Horndeski action which does not propagate any scalar degrees of freedom. Our finding opens a novel window into studies of nontrivial interactions between dark energy/modified gravity theories and astrophysical black holes.

In this work, we study an inflationary scenario in the presence of generalized Chaplygin gas (GCG). We show that in Einstein gravity, GCG is not a suitable candidate for inflation; but in a five-dimensional brane-world scenario, it can work as a viable inflationary model. We calculate the relevant quantities such as $n_s$, $r$, and $A_s$ related to the primordial scalar and tensor fluctuations, and using their recent bounds from Planck and BICEP2, we constrain the model parameters as well as the five-dimensional Planck mass. But as a slow-roll inflationary model with a power-law type scalar primordial power spectrum, GCG as an inflationary model cannot resolve the tension between results from BICEP2 and Planck with a concordance $\mathrm{\Lambda }\mathrm{CDM}$ Universe. We show that by going beyond the concordance $\mathrm{\Lambda }\mathrm{CDM}$ model and incorporating more general dark energy behavior, we may ease this tension. We also obtain the constraints on the $n_s$ and $r$ and the GCG model parameters using $\text{Planck}+\mathrm{WP}+\mathrm{BICEP}2$ data considering the CPL dark energy behavior.