Using the AdS/CFT correspondence for strongly coupled gauge theories, we calculate thermalization of mesons caused by a time-dependent change of a baryon-number chemical potential. On the gravity side, the thermalization corresponds to a horizon formation on the probe flavor brane in the AdS throat. Since heavy-ion collisions are locally approximated by a sudden change of the baryon-number chemical potential, we discuss the implication of our results to RHIC and LHC experiments, to find a rough estimate of the rather rapid thermalization time-scale $t_{\mathrm{th}}<1[\mathrm{fm}/\mathrm{c}]$. We also discuss the universality of our analysis against varying gauge theories.

Prior work using gauge/gravity duality has established the existence of a quantum critical point in the phase diagram of $3+1$-dimensional gauge theories at finite charge density and background magnetic field. The critical theory, obtained by tuning the dimensionless charge density to magnetic field ratio, exhibits nontrivial scaling in its thermodynamic properties, and an associated nontrivial dynamical critical exponent. In the present work, we analytically compute low-energy correlation functions in the background of the charged magnetic brane solution to $4+1$-dimensional Einstein-Maxwell-Chern-Simons theory, which represents the bulk description of the critical point. Results are obtained for neutral scalar operators, the stress tensor, and the $U(1)$-current. The theory is found to exhibit a twisted Virasoro algebra, constructed from a linear combination of the original stress tensor and chiral $U(1)$-current. The effective speed of light in the IR is renormalized downward for one chirality, but not the other, by finite density, a behavior that is consistent with a Luttinger liquid description of fermions in the lowest Landau level. The results obtained here do not directly shed light on the mechanism driving the phase transition, and we comment on why this is so.

We enlarge the usual $D=3$ $\mathcal{N}=1$ supergraph techniques to include the case of (explicitly or spontaneously) broken supersymmetric gauge theories. To illustrate the utility of these techniques, we calculate the two-loop effective potential of the ${\mathrm{SQED}}_3$ by using the tadpole and the vacuum bubble methods. In these methods, to investigate the possibility of supersymmetry breaking, the superfields must be shifted by ${\theta }_{\alpha }$ dependent classical superfields (vacuum expectation values), what implies in the explicit breakdown of supersymmetry in the intermediate steps of the calculation. Nevertheless, after studying the minimum of the resulting effective potential, we find that supersymmetry is conserved, while gauge symmetry is dynamically broken, with a mass generated for the gauge superfield.

A new $q$ deformation of the Euclidean EPRL/FK (Engle-Pereira-Rovelli-Livine/Freidel-Krasnov) vertex amplitude is proposed by using the evaluation of the Vassiliev invariant associated with a 4-simplex graph [related to two copies of quantum SU(2) group at different roots of unity] embedded in a 3-sphere. We show that the large-$j$ asymptotics of the $q$-deformed vertex amplitude gives the Regge action with a cosmological constant. In the end we also discuss its relation with a Chern-Simons theory on the boundary of 4-simplex.

A method is presented which allows for the renormalization of the self-potential for a scalar point charge at rest in static curved space-time. The method is suitable for the scalar field with arbitrary mass $m$ and coupling to the scalar curvature. The asymptotic behavior of self-potential is obtained in the limit in which the Compton wavelength $1/m$ of the massive scalar field is much smaller than the characteristic scale of curvature of the background gravitational field. The self-force is calculated in this limit.

The presence of weak intergalactic magnetic fields can be studied by their effect on electromagnetic cascades induced by multi-TeV $\gamma$ rays in the cosmic radiation background. Small deflections of secondary electrons and positrons as the cascade develops extend the apparent size of the emission region of distant TeV $\gamma$-ray sources. These $\gamma$-ray halos can be resolvable in imaging atmospheric Cherenkov telescopes and serve as a measure of the intergalactic magnetic field strength and coherence length. We present a method of calculating the $\gamma$-ray halo for isotropically emitting sources by treating magnetic deflections in the cascade as a diffusion process. With this ansatz the moments of the halo follow from a set of simple diffusion-cascade equations. The reconstruction of the angular distribution is then equivalent to a classical moment problem. We present a simple solution using Padé approximations of the moment’s generating function.

We present a formalism for performance forecasting and optimization of future cosmic microwave background (CMB) experiments. We implement it in the context of nearly full sky, multifrequency, $B$-mode polarization observations, incorporating statistical uncertainties due to the CMB sky statistics, instrumental noise, as well as the presence of the foreground signals. We model the effects of a subtraction of these using a parametric maximum likelihood technique and optimize the instrumental configuration with predefined or arbitrary observational frequency channels, constraining either a total number of detectors or a focal plane area. We showcase the proposed formalism by applying it to two cases of experimental setups based on the CMBpol and COrE mission concepts looked at as dedicated $B$-mode experiments. We find that, if the models of the foregrounds available at the time of the optimization are sufficiently precise, the procedure can help to either improve the potential scientific outcome of the experiment by a factor of a few, while allowing one to avoid excessive hardware complexity, or simplify the instrument design without compromising its science goals. However, our analysis also shows that even if the available foreground models are not considered to be sufficiently reliable, the proposed procedure can guide a design of more robust experimental setups. While better suited to cope with a plausible, greater complexity of the foregrounds than that foreseen by the models, these setups could ensure science results close to the best achievable, should the models be found to be correct.

A method of resummation of truncated perturbation series, related to diagonal Padé approximants but giving results independent of the renormalization scale, was developed more than ten years ago by us with a view of applying it in perturbative QCD. We now apply this method in analytic QCD models, i.e., models where the running coupling has no unphysical singularities, and we show that the method has attractive features, such as a rapid convergence. The method can be regarded as a generalization of the scale-setting methods of Stevenson, Grunberg, and Brodsky-Lepage-Mackenzie. The method involves the fixing of various scales and weight coefficients via an auxiliary construction of diagonal Padé approximant. In low-energy QCD observables, some of these scales become sometimes low at high order, which prevents the method from being effective in perturbative QCD, where the coupling has unphysical singularities at low spacelike momenta. There are no such problems in analytic QCD.

We study the $Z^{\prime }$ phenomenology for two extensions of the electroweak standard model (SM) which have an extra $U(1{)}_{B-L}$ gauge factor. We show the capabilities of the LHC in distinguishing the signals coming from these two extensions and both of them from the SM background. In order to compare the behavior of these $B-L$ models we consider the reaction $p+p\to {\mu }^{+}+{\mu }^{-}+X$ and compute some observables as the total cross sections, number of events, forward-backward asymmetry, final particle distributions like rapidity, transverse momentum, and dimuon invariant mass, for two LHC regimes: $\sqrt{s}(\mathcal{L})=7\mathrm{TeV}$ ($1{\mathrm{fb}}^{-1}$) and 14 TeV ($100{\mathrm{fb}}^{-1}$) for $M_{Z^{\prime }}=1000\mathrm{GeV}$ and 1500 GeV. We show that by using appropriate kinematic cuts some of the observables considered here, we are able to extract different properties of the $Z^{\prime }$ boson, and hence to provide information about to which $B-L$ model it belongs to.

The recent Tevatron measurement of the forward-backward asymmetry of the top quark shows an intriguing discrepancy with Standard Model expectations, particularly at large $t\overline{t}$ invariant masses. Measurements of this quantity are subtle at the LHC, due to its $pp$ initial state, however, one can define a forward-central-charge asymmetry which captures the physics. We study the capability of the LHC to measure this asymmetry and find that within the SM a measurement at the $5\sigma$ level is possible with roughly $60{\mathrm{fb}}^{-1}$ at $\sqrt{s}=14\mathrm{TeV}$. If nature realizes a model which enhances the asymmetry (as is necessary to explain the Tevatron measurements), a significant difference from zero can be observed much earlier, perhaps even during early LHC running at $\sqrt{s}=7\mathrm{TeV}$. We further explore the capabilities of the 7 TeV LHC to discover resonances or contact interactions which modify the $t\overline{t}$ invariant mass distribution using recent boosted top-tagging techniques. We find that TeV-scale color-octet resonances can be discovered, even with small coupling strengths and that contact interactions can be probed at scales exceeding 6 TeV. Overall, the LHC has good potential to clarify the situation with regards to the Tevatron forward-backward measurement.

We present results from a study of $X(3872)\to \pi \pi J/\psi$ decays produced via exclusive $B\to KX(3872)$ decays. We determine the mass to be $M_{X(3872)}=(3871.85\pm 0.27(\mathrm{stat})\pm 0.19(\mathrm{syst}))\mathrm{MeV}$, a 90% confidence level upper limit on the natural width of ${\Gamma }_{X(3872)}<1.2\mathrm{MeV}$, the product branching fraction $\mathcal{B}(B^{+}\to K^{+}X(3872))\times \mathcal{B}(X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi )=(8.63\pm 0.82(\mathrm{stat})\pm 0.52(\mathrm{syst}))\times {10}^{-6}$, and a ratio of branching fractions $\mathcal{B}(B^0\to K^{0}X(3872))/\mathcal{B}(B^{+}\to K^{+}X(3872))=0.50\pm 0.14(\mathrm{stat})\pm 0.04(\mathrm{syst})$. The difference in mass between the $X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi$ signals in $B^{+}$ and $B^0$ decays is $\Delta M_{X(3872)}=(-0.71\pm 0.96(\mathrm{stat})\pm 0.19(\mathrm{syst}))\mathrm{MeV}$. A search for a charged partner of the $X(3872)$ in the decays ${\overline{B}}^0\to K^{-}{X}^{+}$ or $B^{+}\to K^0{X}^{+}$, $X^{+}\to {\pi }^{+}{\pi }^{0}J/\psi$ resulted in upper limits on the product branching fractions for these processes that are well below expectations for the case that the $X(3872)$ is the neutral member of an isospin triplet. In addition, we examine possible $J^{PC}$ quantum number assignments for the $X(3872)$ based on comparisons of angular correlations between final state particles in $X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi$ decays with simulated data for $J^{PC}$ values of $1^{++}$ and $2^{-+}$. We examine the influence of $\rho$-$\omega$ interference in the $M({\pi }^{+}{\pi }^{-})$ spectrum. The analysis is based on a $711{\mathrm{fb}}^{-1}$ data sample that contains $772\times {10}^6$ $B\overline{B}$ meson pairs collected at the ${\rm Y}(4S)$ resonance in the Belle detector at the KEKB $e^{+}{e}^{-}$ collider.

Many experiments that aim at the direct detection of dark matter are able to distinguish a dominant background from the expected feeble signals, based on some measured discrimination parameter. We develop a statistical model for such experiments using the profile likelihood ratio as a test statistic in a frequentist approach. We take data from calibrations as control measurements for signal and background, and the method allows the inclusion of data from Monte Carlo simulations. Systematic detector uncertainties, such as uncertainties in the energy scale, as well as astrophysical uncertainties, are included in the model. The statistical model can be used to either set an exclusion limit or to quantify a discovery claim, and the results are derived with the proper treatment of statistical and systematic uncertainties. We apply the model to the first data release of the XENON100 experiment, which allows one to extract additional information from the data, and place stronger limits on the spin-independent elastic weakly interacting massive particles nucleon scattering cross section. In particular, we derive a single limit, including all relevant systematic uncertainties, with a minimum of $2.4\times {10}^{-44}{\mathrm{cm}}^2$ for weakly interacting massive particles with a mass of $50\mathrm{GeV}/c^2$.

It is shown that the helicity amplitudes $A_{1/2}$ and $S_{1/2}$ in the $\gamma N\to N(1535)$ reaction, can be well related by $S_{1/2}=-\frac{\sqrt{1+\tau }}{\sqrt{2}}\frac{M_S^2-M^2}{2M_{S}Q}{A}_{1/2}$ in the region $Q^2>2{\mathrm{GeV}}^2$, where $M$ and $M_S$ are the nucleon and $N(1535)$ masses, $q^2=-Q^2$ the four-momentum transfer squared, and $\tau =\frac{Q^2}{(M_S+M{)}^2}$. This follows from the fact that the Pauli-type transition form factor $F_2^{*}$ extracted from the experimental data, turns up to show $F_2^{*}\simeq 0$ for $Q^2>1.5{\mathrm{GeV}}^2$. The observed relation is tested by the experimentally extracted helicity amplitudes and the MAID parametrization (Mainz group). A direct consequence of the relation is that the assumption $|A_{1/2}|\gg |S_{1/2}|$ is not valid for high $Q^2$. Instead, both amplitudes $A_{1/2}$ and $S_{1/2}$ have the same $Q^2$ dependence in the high $Q^2$ region; aside from that $S_{1/2}$ has an extra factor, $-\frac{1}{\sqrt{2}}\frac{M_S-M}{2M_S}$. The origin of this relation is interpreted in a perspective of a quark model.

We consider the flavor evolution of a dense neutrino gas by taking into account both vacuum oscillations and self-interactions of neutrinos. We examine the system from a many-body perspective as well as from the point of view of an effective one-body description formulated in terms of the neutrino polarization vectors. We show that, in the single angle approximation, both the many-body picture and the effective one-particle picture possess several constants of motion. We write down these constants of motion explicitly in terms of the neutrino isospin operators for the many-body case and in terms of the polarization vectors for the effective one-body case. The existence of these constants of motion is a direct consequence of the fact that the collective neutrino oscillation Hamiltonian belongs to the class of Gaudin Hamiltonians. This class of Hamiltonians also includes the (reduced) BCS pairing Hamiltonian describing superconductivity. We point out the similarity between the collective neutrino oscillation Hamiltonian and the BCS pairing Hamiltonian. The constants of motion manifest the exact solvability of the system. Borrowing the well established techniques of calculating the exact BCS spectrum, we present exact eigenstates and eigenvalues of both the many-body and the effective one-particle Hamiltonians describing the collective neutrino oscillations. For the effective one-body case, we show that spectral splits of neutrinos can be understood in terms of the adiabatic evolution of some quasiparticle degrees of freedom from a high-density region where they coincide with flavor eigenstates to the vacuum where they coincide with mass eigenstates. We write down the most general consistency equations which should be satisfied by the effective one-body eigenstates and show that they reduce to the spectral split consistency equations for the appropriate initial conditions.

We build quantum field theory on the thermodynamic master equation for dissipative quantum systems. The vacuum is represented by a thermodynamic equilibrium state in the low-temperature limit. All regularization is consistently provided by a friction mechanism; with decreasing friction parameter, only degrees of freedom on shorter and shorter length scales are damped out of a quantum field theory. No divergent integrals need to be manipulated. Renormalization occurs as a tool to refine perturbation expansions, not to remove divergences. Relativistic covariance is recovered in the final results. We illustrate the proposed thermodynamic approach to quantum fields for the ${\phi }^4$ theory by calculating the propagator and the $\beta$ function, and we offer some suggestions on its application to gauge theories.

We study the properties of the Green’s functions of the fermions in the extremal charged dilatonic black hole proposed by Gubser and Rocha [Phys. Rev. D 81, 046001 (2010)]. We find that many properties seem to be in agreement with that of Fermi liquid. Especially, the dispersion relation is linear. It is very different from that found in the extremal Reissner-Nordström (RN) black hole for massless fermion, which is obviously non-Fermi liquid due to a nonlinear dispersion relation. However, for another scaling behavior of the height of $\mathrm{Im}{G}_{11}$ at the maximum, the scaling exponent is not one, which is at odds with that found in the RN black hole.

We investigate the consistent inclusion of 4D Einstein gravity on a truncated slice of ${\mathrm{AdS}}_5$ whose bulk-gravity and UV scales are much less than the 4D Planck scale, $M_{*}\ll M_{\mathrm{Pl}}$. Such “Little Warped Spaces” have found phenomenological utility and can be motivated by string realizations of the Randall-Sundrum framework. Using the interval approach to brane-world gravity, we show that the inclusion of a large UV-localized Einstein-Hilbert term allows one to consistently incorporate 4D Einstein gravity into the low-energy theory. We detail the spectrum of Kaluza-Klein metric fluctuations and, in particular, examine the coupling of the little radion to matter. Furthermore, we show that Goldberger-Wise stabilization can be successfully implemented on such spaces. Our results demonstrate that realistic low-energy effective theories can be constructed on these spaces, and have relevance for existing models in the literature.