The approximation of the renormalized stress-energy tensor of the quantized massive scalar field in Reissner-Nordström spacetime is constructed. It is achieved by functional differentiation of the first two nonvanishing terms of the Schwinger-DeWitt expansion involving the coincidence limit of the Hadamard-Minakshisundaram-DeWitt-Seely coefficients [$a_3$] and [$a_4$] with respect to the metric tensor. It is shown, by comparison with the existing numerical results, that inclusion of the second-order term leads to substantial improvement of the approximation of the exact stress-energy tensor. The approximation to the field fluctuation, $⟨{\varphi }^2⟩$, is constructed and briefly discussed.

Gravitational wave sources are a promising cosmological standard candle because their intrinsic luminosities are determined by fundamental physics (and are insensitive to dust extinction). They are, however, affected by weak lensing magnification due to the gravitational lensing from structures along the line of sight. This lensing is a source of uncertainty in the distance determination, even in the limit of perfect standard candle measurements. It is commonly believed that the uncertainty in the distance to an ensemble of gravitational wave sources is limited by the standard deviation of the lensing magnification distribution divided by the square root of the number of sources. Here we show that by exploiting the non-Gaussian nature of the lensing magnification distribution, we can improve this distance determination, typically by a factor of 2–3; we provide a fitting formula for the effective distance accuracy as a function of redshift for sources where the lensing noise dominates.

We examine the question as to whether the Palatini $f(R)$ gravity theories permit space-times in which the causality is violated. We show that every perfect-fluid Gödel-type solution of Palatini $f(R)$ gravity with density $\rho$ and pressure $p$ that satisfy the weak energy condition $\rho +p\ge 0$ is necessarily isometric to the Gödel geometry, demonstrating therefore that these theories present causal anomalies in the form of closed timelike curves. This result extends a theorem on Gödel-type models to the framework of Palatini $f(R)$ gravity theory. We concretely examine the Gödel-type perfect-fluid solutions in specific $f(R)=R-\alpha /R^n$ Palatini gravity theory, where the free parameters $\alpha$ and $n$ have been recently constrained by observational data. We show that for positive matter density and for $\alpha$ and $n$ within the interval permitted by the observations, this theory does not admit the Gödel geometry as a perfect-fluid solution of its field equations. In this sense, this theory remedies the causal pathology in the form of closed timelike curves which is allowed in general relativity. We derive an expression for a critical radius $r_c$ (beyond which the causality is violated) for an arbitrary Palatini $f(R)$ theory. The expression makes apparent that the violation of causality depends on the form of $f(R)$ and on the matter content components. We also examine the violation of causality of Gödel-type by considering a single scalar field as the matter content. For this source we show that Palatini $f(R)$ gravity gives rise to a unique Gödel-type solution with no violation of causality.

New particles at the TeV scale can decay hadronically with strongly collimated jets, thus the standard reconstruction methods based on invariant masses of well-separated jets can fail. We discuss how to identify such particles in $pp$ collisions at the LHC using simple jet shapes which help to reduce the contribution of QCD-induced events. We focus on a rather generic example $X\to t\overline{t}\to \mathrm{\text{hadrons}}$, with $X$ being a heavy particle, but the approach is well suited for the reconstruction of other decay channels characterized by a cascade decay of known states.

We calculate the next-to-leading order (NLO) QCD corrections to the $W{H}^0$ production in association with a jet at hadron colliders. We study the impacts of the complete NLO QCD radiative corrections to the integrated cross sections, the scale dependence of the cross sections, and the differential cross sections ($\frac{d\sigma }{d\cos \theta }$, $\frac{d\sigma }{d{p}_T}$) of the final $W$-, Higgs boson and jet. We find that the corrections significantly modify the physical observables, and reduce the scale uncertainty of the leading-order cross section. Our results show that by applying the inclusive scheme with $p_{T,j}^{\mathrm{cut}}=20\mathrm{GeV}$ and taking $m_H=120\mathrm{GeV}$, $\mu ={\mu }_0\equiv \frac{1}{2}(m_W+m_H)$, the $K$-factor is 1.15 for the process $p\overline{p}\to W^{\pm }{H}^{0}j+X$ at the Tevatron, while the $K$-factors for the processes $pp\to W^{-}{H}^{0}j+X$ and $pp\to W^{+}{H}^{0}j+X$ at the LHC are 1.12 and 1.08, respectively. We conclude that to understand the hadronic associated $W{H}^0$ production, it is necessary to study the NLO QCD corrections to the $W{H}^{0}j$ production process which is part of the inclusive $W{H}^0$ production.

We study flavor-conserving radiative decays of double-heavy baryons using a manifestly Lorentz covariant constituent three-quark model. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit. We discuss in some detail hyperfine mixing effects.

The forward-backward asymmetry measurement in top-pair production at the Tevatron is about $2\sigma$ from the standard model prediction. We propose an asymmetric left-right model, which includes a $W^{\prime }$ boson with a right-handed coupling of down to top quark, and a $Z^{\prime }$ boson with diagonal couplings to the up, top, and down quarks with $M_{W^{\prime }}\approx 175\mathrm{GeV}$ and $M_{Z^{\prime }}\approx 900\mathrm{GeV}$. The model accounts for the asymmetry while remaining consistent with the top-pair total cross section and invariant mass distribution.

We study vortex solutions in a holographic model of Herzog, Hartnoll, and Horowitz, with a vanishing external magnetic field on the boundary, as is appropriate for vortices in a superfluid. We study the relevant length scales related to the vortices and how the charge density inside the vortex core behaves as a function of temperature or chemical potential. We extract a critical superfluid velocity from the vortex solutions, study how it behaves as a function of the temperature, and compare it to earlier studies and to the Landau criterion. We also comment on the possibility of a Berezinskii-Kosterlitz-Thouless vortex confinement-deconfinement transition.

We begin an investigation of inhomogeneous structures in holographic superfluids. As a first example, we study domain wall-like defects in the $3+1$ dimensional Einstein-Maxwell-Higgs theory, which was developed as a dual model for a holographic superconductor. In [V. Keränen, E. Keski-Vakkuri, S. Nowling, and K. P. Yogendran, Phys. Rev. D 80, 121901 (2009).], we reported on such “dark solitons” in holographic superfluids. In this work, we present an extensive numerical study of their properties, working in the probe limit. We construct dark solitons for two possible condensing operators and find that both of them share common features with their standard superfluid counterparts. However, both are characterized by two distinct coherence length scales (one for order parameter, one for charge condensate). We study the relative charge depletion factor and find that solitons in the two different condensates have very distinct depletion characteristics.

Quantum field theory is the application of quantum physics to fields. It provides a theoretical framework widely used in particle physics and condensed matter physics. One of the most distinct features of quantum physics with respect to classical physics is entanglement or the existence of strong correlations between subsystems that can even be spacelike separated. In quantum fields, observables restricted to a region of space define a subsystem. While there are proofs on the existence of local observables that would allow a violation of Bell’s inequalities in the vacuum states of quantum fields as well as some explicit but technically demanding schemes requiring an extreme fine-tuning of the interaction between the fields and detectors, an experimentally accessible entanglement witness for quantum fields is still missing. Here we introduce smeared field operators which allow reducing the vacuum to a system of two effective bosonic modes. The introduction of such collective observables is motivated by the fact that no physical probe has access to fields in single spatial (mathematical) points but rather smeared over finite volumes. We first give explicit collective observables whose correlations reveal vacuum entanglement in the Klein-Gordon field. We then show that the critical distance between the two regions of space above which two effective bosonic modes become separable is of the order of the Compton wavelength of the particle corresponding to the massive Klein-Gordon field.

We consider a perturbative treatment, in the regime of weak gauge coupling, of supersymmetric Yang-Mills theory in a space-time of the form $T^3\times \mathbb{R}$ with $\mathrm{SU}(n)/{\mathbb{Z}}_n$ gauge group and a nontrivial gauge bundle. More specifically, we consider the theories obtained as power series expansions around a certain class of normalizable vacua of the classical theory, corresponding to isolated points in the moduli space of flat connections, and the perturbative corrections to the free energy eigenstates and eigenvalues in the weakly interacting theory. The perturbation theory construction of the interacting Hilbert space is complicated by the divergence of the norm of the interacting states. Consequently, the free and interacting Hilbert spaces furnish unitarily inequivalent representations of the algebra of creation and annihilation operators of the quantum theory. We discuss a consistent redefinition of the Hilbert space norm to obtain the interacting Hilbert space and the properties of the interacting representation. In particular, we consider the lowest nonvanishing corrections to the free energy spectrum and discuss the crucial importance of supersymmetry for these corrections to be finite.

Direct gauge mediation models using the Intriligator-Seiberg-Shih metastable vacua suffer from the Landau pole problem of the standard-model gauge couplings and the existence of $R$-symmetry forbidding gaugino masses. These problems may be solved by using the recently proposed supersymmetry (SUSY)-breaking models in a conformal window of the vectorlike $SU(N_C)$ gauge theory with gauge singlets. In this paper we propose a model of gauge mediation based on the SUSY-breaking model in the conformal window, and study the dynamics for SUSY breaking. In this model, there are massive vectorlike bifundamental fields charged under both $SU(N_C)$ and the standard-model gauge group, and our model can be regarded as a semidirect gauge mediation model. The color number $N_C$ can be small to avoid the Landau pole problem, and $R$ symmetry is also broken under a reasonable assumption on the strong dynamics of the model. The model possesses only one free parameter, and the gaugino and sfermion masses are naturally of the same order.

The Chern-Simons modification to general relativity in four dimensions consists of adding to the Einstein-Hilbert term a scalar field that couples to the first-class Pontryagin density. In this theory, which has attracted considerable attention recently, the Schwarzschild metric persists as an exact solution, and this is why this model resists several observational constraints. In contrast, the spinning black hole solution of the theory is not given by the Kerr metric but by a modification of it, so far only known for slow rotation and small coupling constant. In the present paper, we show that, in this approximation, the null geodesic equation can be integrated, and this allows us to investigate the shadow cast by a black hole. We discuss how, in addition to the angular momentum of the solution, the coupling to the Chern-Simons term deforms the shape of the shadow.

Chiral gravity and cosmological birefringence both provide physical mechanisms to produce parity-violating $TB$ and $EB$ correlations in the cosmic microwave background (CMB) temperature/polarization. Here, we study how well these two mechanisms can be distinguished if nonzero $TB/EB$ correlations are found. To do so, we evaluate the correlation matrix, including new $TB\mathrm{\text{−}}EB$ covariances. We find that the effects of these two mechanisms on the CMB are highly orthogonal, and can thus be distinguished fairly well in the case of a high-signal-to-noise detection of $TB/EB$ correlations. Appendix B evaluates the relative sensitivities of the $BB$, $TB$, and $EB$ signals for detecting a chiral gravitational-wave background.

We consider corrections to the underlying cosmology due to secondary contributions from weak gravitational lensing, the integrated Sachs-Wolfe effect, and the Sunyaev-Zel’dovich effect contained in the trispectrum. We incorporate these additional contributions to the covariance of a binned angular power spectrum of temperature anisotropies in the analysis of current and prospective data sets. Although recent experiments such as the Arcminute Cosmology Bolometer Array Receiver and the Cosmic Background Imager are not particularly sensitive to these additional non-Gaussian effects, the interpretation of Planck and CMBPol anisotropy spectra will require an accounting of non-Gaussian covariance leading to a degradation in cosmological parameter estimates by up to 20% and 30%, respectively.

By the application of the generalized Israel junction conditions we derive cosmological equations for the fourth-order $f(R)$ brane gravity and study their cosmological solutions. We show that there exists a nonstatic solution which describes a four-dimensional de Sitter $({\mathrm{dS}}_4)$ brane embedded in a five-dimensional anti-de Sitter $({\mathrm{AdS}}_5)$ bulk for a vanishing Weyl tensor contribution. On the other hand, for the case of a nonvanishing Weyl tensor contribution, there exists a static brane solution only. We claim that in order to get some more general nonstatic $f(R)$ brane configurations, one needs to admit a dynamical matter energy-momentum tensor in the bulk rather than just a bulk cosmological constant.

Motivated by dark-matter considerations in supersymmetric theories, we investigate in a fairly model-independent way the detection at the LHC of nearly degenerate gauginos with mass differences between a few GeV and about 30 GeV. Because of the degeneracy of gaugino states, the conventional leptonic signals are likely lost. We first consider the leading signal from gluino production and decay. We find that it is quite conceivable to reach a large statistical significance for the multijet plus missing energy signal with an integrated luminosity about $50{\mathrm{pb}}^{-1}$ ($50{\mathrm{fb}}^{-1}$) for a gluino mass of 500 GeV (1 TeV). If gluinos are not too heavy, less than about 1.5 TeV, this channel can typically probe gaugino masses up to about 100 GeV below the gluino mass. We then study the Drell-Yan type of gaugino pair production in association with a hard QCD jet, for gaugino masses in the range of 100–150 GeV. The signal observation may be statistically feasible with about $10{\mathrm{fb}}^{-1}$, but systematically challenging due to the lack of distinctive features for the signal distributions. By exploiting gaugino pair production through weak boson fusion, signals of large missing energy plus two forward-backward jets may be observable at a $4–6\sigma$ level above the large SM backgrounds with an integrated luminosity of $100–300{\mathrm{fb}}^{-1}$. Finally, we point out that searching for additional isolated soft muons in the range $p_T\sim 3–10\mathrm{GeV}$ in the data samples discussed above may help to enrich the signal and to control the systematics. Significant efforts are made to explore the connection between the signal kinematics and the relevant masses for the gluino and gauginos, to probe the mass scales of the superpartners, in particular, the lightest supersymmetric particle dark matter.

We investigate the prospects for indirect detection of fermion WIMPless dark matter at the neutrino telescopes IceCube and DeepCore. The dark matter annihilating in the Sun is a hidden sector Majorana fermion that couples through Yukawa couplings to a connector particle and a visible sector particle, and it exhibits only spin-dependent scattering with nuclei via couplings to first generation quarks. We consider cases where the annihilation products are taus, staus, or sneutrinos of the three generations. To evaluate the muon fluxes incident at the detector, we propagate the neutrino spectra through the solar medium and to the Earth and account for the effects of neutrino oscillations, energy losses due to neutral- and charged-current interactions, and tau regeneration. We find that for the stau and sneutrino channels, a 5 yr $3\sigma$ detection of dark matter lighter than about 300 GeV is possible at IceCube for large Yukawa couplings or for dark matter and connector particles with similar masses. The tau channel offers far better detection prospects. However, due to its lower energy threshold and better muon background rejection capability, DeepCore is able to detect signals in all annihilation channels and for a wider range of dark matter masses.

We present results for one-loop perturbative matching factors using bilinear operators composed of improved staggered fermions, using unimproved (Wilson) and improved (Symanzik, Iwasaki, and DBW2) gluon actions. We consider two fermions actions—HYP/$\overline{\mathrm{Fat}7}$-smeared and asqtad. The former is being used in calculations of electroweak matrix elements, while the latter have been used extensively by the MILC collaboration. We observe that using the improved gluon action leads to small reductions in the perturbative corrections, but that these reductions are smaller than those obtained when moving from the tadpole-improved naive staggered action to either HYP-smeared or asqtad action.

The decay widths of top quark to S-wave $b\overline{c}$ and $b\overline{b}$ bound states are evaluated at the next-to-leading-order accuracy in strong interaction. Numerical calculation shows that the next-to-leading-order corrections to these processes are remarkable. The QCD renormalization scale dependence of the results is obviously depressed, and hence the uncertainties lying in the leading order calculation are reduced.