We use the recent measurements of top quark decay asymmetries in ATLAS and the $t$-channel single top cross section in CMS to set the first combined LHC limits on the $Wtb$ vertex. This combination allows us to obtain much better limits than the separate measurements. The resulting constraints are comparable, although still weaker, than the ones obtained using Tevatron data with much more statistics.

We use the early Large Hadron Collider data to set the lower limit on the scale of left-right symmetry, by searching for the right-handed charged gauge boson $W_R$ via the final state with two leptons and two jets, for $33{\mathrm{pb}}^{-1}$ integrated luminosity and 7 TeV center-of-mass energy. This signal is kinematically observable for right-handed neutrino lighter than $W_R$. In the absence of a signal beyond the standard model background, we set the bound $M_{W_R}\gtrsim 1.4\mathrm{TeV}$ at 95% C.L.. This result is obtained for a range of right-handed neutrino masses of the order of few 100 GeV, assuming no accidental cancellation in right-handed lepton mixings.

The QCD phase diagram is studied in the lattice QCD simulation with the imaginary chemical potential approach. We employ a clover-improved Wilson fermion action of two flavors and a renormalization-group improved gauge action and perform the simulation at an intermediate quark mass on a $8^3\times 4$ lattice. The QCD phase diagram in the imaginary chemical potential ${\mu }_I$ region is investigated by performing the simulation for more than 150 points on the $(\beta ,{\mu }_I)$ plane. We find that the Roberge-Weiss phase transition at ${\mu }_I/T=\pi /3$ is first order and its endpoint is second order, which are identified by the phase of the Polyakov loop. We determine the pseudocritical line from the susceptibility of the Polyakov loop modulus. We find a clear deviation from a linear dependence of the pseudocritical line on ${\mu }_I^2$.

The strange quark content of the nucleon $⟨N|\overline{s}s|N⟩$ is calculated in dynamical lattice QCD employing the overlap fermion formulation. For this quantity, exact chiral symmetry guaranteed by the Ginsparg-Wilson relation is crucial to avoid large contamination due to a possible operator mixing with $\overline{u}u+\overline{d}d$. Gauge configurations are generated with two dynamical flavors on a ${16}^3\times 32$ lattice at a lattice spacing $a\simeq 0.12\mathrm{fm}$. We directly calculate the relevant three-point function on the lattice including a disconnected strange quark loop utilizing the techniques of the all-to-all quark propagator and low-mode averaging. Our result $f_{T_s}=m_s⟨N|\overline{s}s|N⟩/M_N=0.032(8{)}_{\mathrm{stat}}(22{)}_{\mathrm{sys}}$, where $m_s$ and $M_N$ are strange quark and nucleon masses, is in good agreement with our previous indirect estimate using the Feynman-Hellmann theorem.

The Collider Detector at Fermilab (CDF) has observed a top forward-backward asymmetry discrepant with the standard model prediction at $3.4\sigma$. We analyze models that could generate the asymmetry, including flavor-violating $W^{\prime }$s, horizontal $Z_H^{\prime }$s, triplet and sextet diquarks, and axigluons. We consider the detailed predictions of these models for the invariant mass and rapidity distributions of the asymmetry at the parton level, comparing against the unfolded parton-level CDF results. While all models can reproduce the asymmetry with the appropriate choice of mass and couplings, it appears at first examination that the extracted parton-level invariant mass distributions for all models are in conflict with Tevatron observations. We show, however, that, on closer examination, $t\overline{t}$ events in $Z_H^{\prime }$ and $W^{\prime }$ models have considerably lower selection efficiencies in high invariant mass bins as compared to the standard model, so that $W^{\prime }$, $Z_H^{\prime }$, and axigluon models can generate the observed asymmetry while being consistent with the total cross-section and invariant mass spectrum. Triplet and sextet models have greater difficulty producing the observed asymmetry while remaining consistent with the total cross-section and invariant mass distribution. To more directly match the models and the CDF results, we proceed to decay and reconstruct the tops, comparing our results against the raw CDF asymmetry and invariant mass distributions. We find that the models that successfully generate the corrected CDF asymmetry at the parton level reproduce the more finely binned uncorrected asymmetry very well. Finally, we discuss the early LHC reach for discovery of these models, based on our previous analysis [M. I. Gresham, I.-W. Kim, and K. M. Zurek, arXiv:1102.0018.].

New heavy gauge bosons exist in many models of new physics beyond the standard model of particle physics. Discovery of these $W^{\prime }$ and $Z^{\prime }$ resonances and the establishment of their spins, couplings, and other quantum numbers would shed light on the gauge structure of the new physics. The measurement of the polarization of the SM fermions from the gauge boson decays would decipher the handedness of the coupling of the new states, an important relic of the primordial new physics symmetry. Since the top quark decays promptly, its decay preserves spin information. We show how decays of new gauge bosons into third generation fermions ($W^{\prime }\to tb$, $Z^{\prime }\to t\overline{t}$) can be used to determine the handedness of the couplings of the new states and to discriminate among various new physics models.

In the electromagnetism of loop quantum gravity, two helicities of a photon have different phase velocities and group velocities, termed as “vacuum birefringence”. Two novel phenomenons, “peak doubling” and “depolarization”, are expected to appear for a linearly polarized light from astrophysical sources. We show that the criteria to observe these two phenomenons are the same. Further, from recently observed $\gamma$-ray polarization from Cygnus X-1, we obtain an upper limit $\sim 8.7\times {10}^{-12}$ for the Lorentz-violating parameter $\chi$, which is the most firm constraint from well-known systems. We also suggest analyzing the possible existence of “peak doubling” through Fermi-LAT gamma-ray bursts.

We investigate the analytical properties of the s-wave and p-wave holographic insulator/superconductor phase transitions at zero temperature. In the probe limit, we analytically calculate the critical chemical potentials at which the insulator/superconductor phase transition occurs. Those resulting analytical values perfectly match the previous numerical values. We also study the relations between the condensation values and the chemical potentials near the critical point. We find that the critical exponent for condensation operator is $1/2$ for both models. The linear relations between the charge density and the chemical potential near the critical point are also deduced in this paper, which are qualitatively consistent with the previous numerical results.

Gravitational backgrounds in $d+2$ dimensions have been proposed as holographic duals to Lifshitz-like theories describing critical phenomena in $d+1$ dimensions with critical exponent $z\ge 1$. We numerically explore a dilaton Einstein-Maxwell model, admitting such backgrounds as solutions. Such backgrounds are characterized by a temperature $T$ and chemical potential $\mu$, and we find how to embed these solutions into anti-de Sitter (AdS) for a range of values of $z$ and $d$. We find no thermal instability going from the $T\ll \mu$ to the $T\gg \mu$ regimes, regardless of the dimension, and find that the solutions smoothly interpolate between Lifshitz-like behavior and relativistic AdS-like behavior. We show, using some conserved, that the energy density $\mathcal{E}$, entropy density $s$, and number density $n$ are related via $\mathcal{E}=\frac{d}{d+1}(Ts+\mu n)$, as is required by the isometries of ${\mathrm{AdS}}_{d+2}$. Finally, in the $T\ll \mu$ regime, the entropy density is found to satisfy a power law $s\propto c{T}^{d/z}{\mu }^{(z-1)d/z}$, and we numerically explore the dependence of the constant $c$, a measure of the number of degrees of freedom, on $d$ and $z$.

We consider non-Abelian semilocal strings (vortices or vortex strings) arising in $\mathcal{N}=2$ supersymmetric $U(N)$ gauge theory with $N_f=N+\tilde{N}$ matter hypermultiplets in the fundamental representation (quarks) and a Fayet-Iliopoulos term $\xi$. We present, for the first time ever, a systematic field-theoretic derivation of the world-sheet theory for such strings, describing dynamics of both orientational and size-zero modes. Our derivation is complete in the limit $(\ln L)\to \infty$, where $L$ is an infrared regulator in the transverse plane. In this limit, the world-sheet theory is obtained exactly. It is presented by a so-far unknown $\mathcal{N}=2$ two-dimensional sigma model, to which we refer as the $zn$ model, with or without twisted masses. Alternative formulations of the $zn$ model are worked out: conventional and extended gauged formulations and a geometric formulation. We compare the exact metric of the $zn$ model with that of the weighted $CP(N_f-1)$ model conjectured by Hanany and Tong, through $D$ branes, as the world-sheet theory for the non-Abelian semilocal strings. The Hanany-Tong setup has no parallel for the field-theoretic infrared parameter, and metrics of the weighted $CP(N_f-1)$ model and $zn$ model are different. Still, their quasiclassical excitation spectra coincide.

We calculate the one-loop effective potential at finite temperature for a system of massless scalar fields with quartic interaction $\lambda {\varphi }^4$ in the framework of the boundary effective theory formalism. The calculation relies on the solution of the classical equation of motion for the field and Gaussian fluctuations around it. Our result is nonperturbative and differs from the standard one-loop effective potential for field values larger than $T/\sqrt{\lambda }$.

One may write the Maxwell equations in terms of two gauge potentials, one electric and one magnetic, by demanding that their field strengths should be dual to each other. This requirement is the condition of twisted self-duality. It can be extended to $p$-forms in spacetime of $D$ dimensions, and it survives the introduction of a variety of couplings among forms of different rank, and also to spinor and scalar fields, which emerge naturally from supergravity. In this paper we provide a systematic derivation of the action principle, whose equations of motion are the condition of twisted self-duality. The derivation starts from the standard Maxwell action, extended to include the aforementioned couplings, and proceeds via the Hamiltonian formalism through the resolution of Gauss’s law. In the pure Maxwell case we recover in this way an action that had been postulated by other authors, through an ansatz based on an action given earlier by us for untwisted self-duality. When Chern-Simons couplings are included, our action is, however, new. The derivation from the standard extended Maxwell action implies of course that the theory is Lorentz invariant and can be locally coupled to gravity. Nevertheless we include a direct compact Hamiltonian proof of these properties, which is based on the surface-deformation algebra. The symmetry in the dependence of the action on the electric and magnetic variables is manifest, since they appear as canonical conjugates. Spacetime covariance, although present, is not manifest.

Gravity is the weakest force in nature, and the gravitational interactions with all standard model (SM) particles can be well described by perturbative expansions of the Einstein-Hilbert action as an effective theory, all the way up to energies below the fundamental Planck scale. We use the Vilkovisky-DeWitt method to derive the first gauge-invariant nonzero gravitational power-law corrections to the Callan-Symanzik beta functions which make both Abel and non-Abel gauge interactions asymptotically free. We further demonstrate that the graviton-induced universal power-law runnings always assist the three SM gauge forces to reach unification around the Planck scale, irrespective of the detail of logarithmic corrections. We further compute the power-law corrections to the SM Higgs sector and derive modified triviality bound on the Higgs boson mass.

The discontinuities of electromagnetic test fields generated by general layers of electric and magnetic monopoles and dipoles are investigated in general curved spacetimes. The equivalence of electric currents and magnetic dipoles is discussed. The results are used to describe exact “Schwarzschild disk” solutions endowed with such sources. The resulting distributions of charge and dipole densities on the disks are corroborated using the membrane paradigm.

It is well known that quasilocal black hole horizons depend on the choice of a time coordinate in a spacetime. This has implications for notions such as the surface of the black hole and also on quasilocal physical quantities such as horizon measures of mass and angular momentum. In this paper, we compare different horizons on nonspherically symmetric slicings of Vaidya spacetimes. The spacetimes we investigate include both accreting and evaporating black holes. For some simple choices of the Vaidya mass function corresponding to collapse of a hollow shell, we compare the area for the numerically found axisymmetric trapping horizons with the area of the spherically symmetric trapping horizon and event horizon. We find that, as expected, both the location and area are dependent on the choice of foliation. However, the area variation is not large, of order 0.017% for a slowly evolving horizon with $\dot{m}=0.02$. We also calculate analytically the difference in area between the spherically symmetric quasilocal horizon and event horizon for a slowly accreting black hole. We find that the difference can be many orders of magnitude larger than the Planck area for sufficiently large black holes.

We consider Hořava–Lifshitz gravity in both $1+1$ and $2+1$ dimensions. These lower-dimensional versions of Hořava–Lifshitz gravity are simple enough to be explicitly tractable, but still complex enough to be interesting. We write the most general (nonprojectable) action for each case and discuss the resulting dynamics. In the $1+1$ case we utilize the equivalence with 2-dimensional Einstein-aether theory to argue that, even though nontrivial, the theory does not have any local degrees of freedom. In the $2+1$ case, we show that the only dynamical degree of freedom is a scalar, which qualitatively has the same dynamical behavior as the scalar mode in (nonprojectable) Hořava–Lifshitz gravity in $3+1$ dimensions. We discuss the suitability of these lower-dimensional theories as simpler playgrounds that could help us gain insight into the $3+1$ theory. As special cases, we also discuss the projectable limit of these theories. Finally, we present an algorithm that extends the equivalence with (higher-order) Einstein-aether theory to full Hořava–Lifshitz gravity (instead of just the low-energy limit), and we use this extension to comment on the apparent naturalness of the covariant formulation of the latter.

The geodesics of massless particles produced in collisions near a rotating black hole are solved numerically and a Monte Carlo integration of the momentum distribution of the massless particles is performed to calculate the fraction that escape the black hole to infinity. A distribution of in falling dark matter particles, which are assumed to annihilate to massless particles, is considered and an estimate of the emergent flux from the collisions is made. The energy spectrum of the emergent particles is found to contain two Lorentz shifted peaks centered on the mass of the dark matter. The separation of the peaks is found to depend on the density profile of the dark matter and could provide information about the size of the annihilation plateau around a black hole and the mass of the dark matter particle.

New gauge bosons with standard model-like couplings to leptons are constrained by collider searches to be heavier than approximately $\sim 1\mathrm{TeV}$. A $Z^{\prime }$ boson with suppressed couplings to leptons, however, could be much lighter and possess substantial couplings to standard model quarks. In this article, we consider a new leptophobic $Z^{\prime }$ gauge boson as a simple and well-motivated extension of the standard model, and discuss several of its possible signatures at the Tevatron. We find that three of the recent anomalies reported from the Tevatron—in particular, the top-quark forward-backward asymmetry and excesses in the $3b$ and $W+2$ jets final states—could be explained by a new $Z^{\prime }$ with a mass of approximately 150 GeV, relatively large couplings to quarks, and suppressed couplings to electrons and muons. Moreover, we find that such a particle could also mediate the interactions of dark matter, leading to potentially interesting implications for direct detection experiments.

We study the potential to observe $CP$-violating effects in supersymmetric ${\tilde{t}}_1$-cascade decay chains at the LHC. Asymmetries composed of triple products of momenta of the final-state particles are sensitive to $CP$-violating effects. Because of large boosts that dilute the asymmetries, these can be difficult to observe. If all particle masses in a cascade decay are known, it may be possible to reconstruct all momenta in the decay chains on an event-by-event basis even when we have missing momentum due to a stable lightest supersymmetric particle. After the reconstruction, the nondiluted $CP$-violating signal can be recovered and gets significantly enhanced so that an observation may become feasible. A fully hadronic study has been completed to define the areas of the minimal supergravity parameter space that may yield a $3\mathrm{\text{−}}\sigma$ observation with $500{\mathrm{fb}}^{-1}$ at the LHC.

We embed the next-to minimal supersymmetric standard model into gauge mediation of supersymmetry breaking and study the phenomenology of scenarios where the gauge-mediation contributions to soft parameters are deflected by superpotential interactions of the gauge singlet with the messenger fields and the Higgs doublets. This kind of models provides a satisfactory solution to the $\mu \mathrm{\text{−}}{b}_{\mu }$ problem of gauge mediation, compatible with the adequate pattern of electroweak symmetry breaking and a realistic spectrum with supersymmetric partners at the TeV scale without requiring a significant fine tuning.