Massive Excitations Research Articles

THE MOSDEF SURVEY: OPTICAL ACTIVE GALACTIC NUCLEUS DIAGNOSTICS ATz∼ 2.3

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on rest-frame optical AGN identification and completeness at z~2.3. With our sample of 50 galaxies and 10 X-ray and IR-selected AGN with measured H-beta, [OIII], H-alpha, and [NII] emission lines, we investigate the location of AGN in the BPT, MEx (mass-excitation), and CEx (color-excitation) diagrams. We find that the BPT diagram works well to identify AGN at z~2.3 and that the z~0 AGN/star-forming galaxy classifications do not need to shift substantially at z~2.3 to robustly separate these populations. However, the MEx diagram fails to identify all of the AGN identified in the BPT diagram, and the CEx diagram is substantially contaminated at high redshift. We further show that AGN samples selected using the BPT diagram have selection biases in terms of both host stellar mass and stellar population, in that AGN in low mass and/or high specific star formation rate galaxies are difficult to identify using the BPT diagram. These selection biases become increasingly severe at high redshift, such that optically-selected AGN samples at high redshift will necessarily be incomplete. We also find that the gas in the narrow-line region appears to be more enriched than gas in the host galaxy for at least some MOSDEF AGN. However, AGN at z~2 are generally less enriched than local AGN with the same host stellar mass.

Vigorous thermal excitations in a double-tetrahedral chain of localized Ising spins and mobile electrons mimic a temperature-driven first-order phase transition.

A hybrid spin-electron system defined on a one-dimensional double-tetrahedral chain, in which the localized Ising spin regularly alternates with two mobile electrons delocalized over a triangular plaquette, is exactly solved with the help of generalized decoration-iteration transformation. It is shown that a macroscopic degeneracy of ferromagnetic and ferrimagnetic ground states arising from chiral degrees of freedom of the mobile electrons cannot be lifted by a magnetic field in contrast to a macroscopic degeneracy of the frustrated ground state, which appears due to a kinetically driven frustration of the localized Ising spins. An anomalous behavior of all basic thermodynamic quantities can be observed on account of massive thermal excitations, which mimic a temperature-driven first-order phase transition from the nondegenerate frustrated state to the highly degenerate ferrimagnetic state at nonzero magnetic fields. A substantial difference in the respective degeneracies is responsible for an immense low-temperature peak of the specific heat and very abrupt (almost discontinuous) thermal variations of the entropy and sublattice magnetizations.

Violation of the spin-statistics theorem and the bose-einstein condensation of particles with half-integer spin.

We consider the Bose condensation of bosonic particles with spin 1/2. The condensation is driven by an external magnetic field. Our work is motivated by ideas of quantum critical deconfinement and bosonic spinons in spin liquid states. We show that both the nature of the novel Bose condensate and the excitation spectrum are fundamentally different from that in the usual integer spin case. We predict two massive ("Higgs") excitations and two massless Goldstone excitations. One of the Goldstone excitations has a linear excitation spectrum and another has a quadratic spectrum. This implies that the Bose condensate does not support superfluidity, the Landau criterion is essentially violated. We formulate a "smoking gun" criterion for searches of the novel Bose condensation.

The neuroprotective effects of (S)-3,5-dihydroxyphenylglycine preconditioning in middle cerebral artery occluded rats: a perspective as a contrivance for stroke.

The neuroprotective effects of (S)-3,5-dihydroxyphenylglycine preconditioning in middle cerebral artery occluded rats: a perspective as a contrivance for stroke.

Quantum mass acquisition in spinor Bose-Einstein condensates.

Quantum mass acquisition, in which a massless (quasi)particle becomes massive due to quantum corrections, is predicted to occur in several subfields of physics. However, its experimental observation remains elusive since the emergent energy gap is too small. We show that a spinor Bose-Einstein condensate is an excellent candidate for the observation of such a peculiar phenomenon as the energy gap turns out to be 2 orders of magnitude larger than the zero-point energy. This extraordinarily large energy gap is a consequence of the dynamical instability. The propagation velocity of the resultant massive excitation mode is found to be decreased by the quantum corrections as opposed to phonons.

String resonances at hadron colliders

We consider extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. Assuming that the fundamental string mass scale ${M}_{s}$ is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (integrated $\mathrm{luminosity}=3000\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$) with a center-of-mass energy of $\sqrt{s}=14\text{ }\text{ }\mathrm{TeV}$ and at potential future $pp$ colliders, HE-LHC and VLHC, operating at $\sqrt{s}=33$ and 100 TeV, respectively (with the same integrated luminosity). In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and $\ensuremath{\gamma}+\mathrm{jet}$ are completely independent of the details of compactification and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first $(n=1)$ and second $(n=2)$ resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV) lowest massive Regge excitations are open to discovery at the $\ensuremath{\ge}5\ensuremath{\sigma}$ in dijet ($\ensuremath{\gamma}+\mathrm{jet}$) HL-LHC data. We also show that for $n=1$ the dijet discovery potential at HE-LHC and VLHC exceedingly improves: up to 15 TeV and 41 TeV, respectively. To compute the signal-to-noise ratio for $n=2$ resonances, we first carry out a complete calculation of all relevant decay widths of the second massive level string states (including decays into massless particles and a massive $n=1$ and a massless particle), where we rely on factorization and conformal field theory techniques. Helicity wave functions of arbitrary higher spin massive bosons are also constructed. We demonstrate that for string scales ${M}_{s}\ensuremath{\lesssim}10.5\text{ }\text{ }\mathrm{TeV}$ (${M}_{s}\ensuremath{\lesssim}28\text{ }\text{ }\mathrm{TeV}$) detection of $n=2$ Regge recurrences at HE-LHC (VLHC) would become the smoking gun for D-brane string compactifications. Our calculations have been performed using a semianalytic parton model approach which is cross checked against an original software package. The string event generator interfaces with HERWIG and Pythia through BlackMax. The source code is publicly available in the hepforge repository.

(2+1)-dimensional Yang-Mills theory and form factor perturbation theory

We study Yang Mills theory in $2+1$ dimensions, as an array of coupled ($1+1$)-dimensional principal chiral sigma models. This can be understood as an anisotropic limit where one of the space-time dimensions is discrete and the others are continuous. The $SU(N)\ifmmode\times\else\texttimes\fi{}SU(N)$ principal chiral sigma model in $1+1$ dimensions is integrable, asymptotically free and has massive excitations. New exact form factors and correlation functions of the sigma model have recently been found by the author and P. Orland. In this paper, we use these new results to calculate physical quantities in ($2+1$)-dimensional Yang-Mills theory, generalizing previous $SU(2)$ results by Orland, which include the string tensions and the low-lying glueball spectrum. We also present a new approach to calculate two-point correlation functions of operators using the light glueball states. The anisotropy of the theory yields different correlation functions for operators separated in the ${x}^{1}$ and ${x}^{2}$ directions.

Fundamental composite Higgs dynamics on the lattice: SU(2) with two flavors

In reference [1] a unified description, both at the effective and fundamental Lagrangian level, of models of composite Higgs dynamics was proposed. In the unified framework the Higgs itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation of the condensate. The most minimal fundamental description consists of an SU(2) gauge theory with two Dirac fermions transforming according to the defining representation of the gauge group. We therefore provide first principle lattice results for the massive spectrum of this theory. We confirm the chiral symmetry breaking phenomenon and determine the lightest spin-one axial and vector masses. The knowledge of the energy scale at which new states will appear at the Large Hadron Collider is of the utmost relevance to guide experimental searches of new physics.

Magnetic exchange interaction in topological insulators

The effective Hamiltonian that describes magnetic exchange interaction in a topological insulator is calculated, projecting bulk contact $s$-$d$ interaction onto surface electron states. This model consistently describes the indirect exchange between magnetic atoms mediated either by massless Dirac fermions in thick films or by massive excitations in a thin slab with tunneling between opposite surfaces. It is shown that an effective $s$-$d$ exchange is sensitive to the symmetry of surface wave functions and depends on the position of an impurity spin relative to slab surfaces. Under a vertical bias the indirect exchange between localized spins is switchable between opposite surfaces, and the oscillating range function reveals zero magnetic field beating as a signature of Rashba spin splitting.

Bound states in disclinated graphene with Coulomb impurities in the presence of a uniform magnetic field

Abstract In this contribution, we study the effects caused by an impurity on the quantum dynamics of massive excitations in a disclinated graphene in the presence of an external magnetic field. Within a continuum approach, the problem is mathematically modeled by the definition of a special vector potential containing all the information about the topology and the interacting fields. The presence of disclination is introduced by a term in the Dirac equation that translates the appearance of a phase associated with the transport of the spinor around the apex of the cone. We solve exactly the Dirac equation for this problem and the eigenvalues are obtained. We observe the influence of the disclination on the spectrum of energy and the allowed values of magnetic field.

ACTIVE GALACTIC NUCLEI EMISSION LINE DIAGNOSTICS AND THE MASS-METALLICITY RELATION UP TO REDSHIFTz∼ 2: THE IMPACT OF SELECTION EFFECTS AND EVOLUTION

Emission line diagnostic diagrams probing the ionization sources in galaxies, such as the Baldwin-Phillips-Terlevich (BPT) diagram, have been used extensively to distinguish AGN from purely star-forming galaxies. Yet, they remain poorly understood at higher redshifts. We shed light on this issue with an empirical approach based on a z~0 reference sample built from ~300,000 SDSS galaxies, from which we mimic selection effects due to typical emission line detection limits at higher redshift. We combine this low-redshift reference sample with a simple prescription for luminosity evolution of the global galaxy population to predict the loci of high-redshift galaxies on the BPT and Mass-Excitation (MEx) diagnostic diagrams. The predicted bivariate distributions agree remarkably well with direct observations of galaxies out to z~1.5, including the observed stellar mass-metallicity (MZ) relation evolution. As a result, we infer that high-redshift star-forming galaxies are consistent with having "normal" ISM properties out to z~1.5, after accounting for selection effects and line luminosity evolution. Namely, their optical line ratios and gas-phase metallicities are comparable to that of low-redshift galaxies with equivalent emission-line luminosities. In contrast, AGN narrow-line regions may show a shift toward lower metallicities at higher redshift. While a physical evolution of the ISM conditions is not ruled out for purely star-forming galaxies, and may be more important starting at z>2, we find that reliably quantifying this evolution is hindered by selections effects. The recipes provided here may serve as a basis for future studies toward this goal. Code to predict the loci of galaxies on the BPT and MEx diagnostic diagrams, and the MZ relation as a function of emission line luminosity limits, is made publicly available.

Fundamental composite (Goldstone) Higgs dynamics

We provide a unified description, both at the effective and fundamental Lagrangian level, of models of composite Higgs dynamics where the Higgs itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation of the condensate. We show that, in general, these states mix with repercussions on the electroweak physics and phenomenology. Our results will help clarify the main differences, similarities, benefits and shortcomings of the different ways one can naturally realize a composite nature of the electroweak sector of the Standard Model. We will analyze the minimal underlying realization in terms of fundamental strongly coupled gauge theories supporting the flavor symmetry breaking pattern SU(4)/Sp(4) $\sim$ SO(6)/SO(5). The most minimal fundamental description consists of an SU(2) gauge theory with two Dirac fermions transforming according to the fundamental representation of the gauge group. This minimal choice enables us to use recent first principle lattice results to make the first predictions for the massive spectrum for models of composite (Goldstone) Higgs dynamics. These results are of the upmost relevance to guide searches of new physics at the Large Hadron Collider.

NEBULAR EXCITATION INz∼ 2 STAR-FORMING GALAXIES FROM THE SINS AND LUCI SURVEYS: THE INFLUENCE OF SHOCKS AND ACTIVE GALACTIC NUCLEI

Based on high-resolution, spatially resolved data of 10 z~2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGN), shocks and photoionization. We explore how these spatially-resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the `composite' region of the z~0 [NII]/Ha versus [OIII]/Hb diagnostic (BPT) diagram, between star-forming galaxies and those with AGN. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from enhanced ionization parameter as compared with HII regions in normal local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [OIII]/Hb versus stellar mass plane, does not properly separate z~2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z~2 mass-metallicity relation (i.e. to the mass they would have at z~0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [NII]/Ha are more biased by shocks and AGN at high-z than the [OIII]/Hb/[NII]/Ha calibration.

Randall-Sundrum scenario with a small curvature and Drell-Yan process at the LHC

The Randall-Sundrum-like scenario with the small curvature $\ensuremath{\kappa}$ (RSSC model) is studied in detail in comparison with the original RS1 model. In the framework of the RSSC model, the ${p}_{\ensuremath{\perp}}$ distributions for dilepton production at the LHC are calculated. Both dielectron and dimuon events are taken into account. The important feature of calculations is the account of the widths of massive graviton excitations. For the summary statistics taken at 7 TeV ($L=5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$) and 8 TeV ($L=20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$), the exclusion limit on the five-dimensional gravity scale ${M}_{5}$ is set to be 6.84 TeV at 95% C.L. For $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ and integrated luminosity $30\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, the LHC search limit is found to be 10.16 TeV. These bounds on ${M}_{5}$ are independent of $\ensuremath{\kappa}$ (up to powerlike corrections), provided $\ensuremath{\kappa}\ensuremath{\ll}{M}_{5}$.

Scattering in AdS2/CFT1 and the BES phase

We study worldsheet scattering for the type IIA superstring in AdS(2) x S(2) x T(6). Using the Green--Schwarz action to quartic order in fermions we take the near-BMN limit, where as in the AdS(3)/CFT(2) case there are both massive and massless excitations. For the massive excitations we compute all possible tree-level processes, and show that these agree with a truncated version of the exact AdS(5) x S(5) S-matrix. We also compute several S-matrix elements involving massless excitations. At one loop we find that the dressing phase is the same Hernandes-Lopez phase appearing in AdS(5)/CFT(4). We see the same phase when calculating this by semiclassical means using the PSU(1,1|2)/U(1)^2 coset sigma model, for which we can also study the scattering of fermions. This supports the conjecture that the all-loop dressing phase is again the BES phase, rather than a new phase like that seen in AdS(3)/CFT(2).

AGN Absorption Linked to Host Galaxies

AbstractMultiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3<z<1, and using AGN tracers in the X-ray, optical spectra, mid-infrared, and radio regimes, we found a twice higher AGN fraction than previous studies, thanks to the combined AGN identification methods and in particular the recent Mass-Excitation (MEx) diagnostic diagram. We furthermore find an intriguing relation between AGN X-ray absorption and the specific star formation rate (sSFR) of the host galaxies, indicating a physical link between X-ray absorption and either the gas fraction or the gas geometry in the hosts. These findings have implications for our current understanding of both the AGN unification model and the nature of the black hole-galaxy connection.

Three- and four-point correlators of excited bosonic twist fields

Abstract We compute three- and four-point correlation functions containing excited bosonic twist fields. Our results can be used to determine properties, such as lifetimes and production rates, of massive string excitations localised at D-brane intersections, which could be signatures of a low string scale even if the usual string resonances are inaccessible to the LHC.

Critical higher order gravities in higher dimensions

We show that the higher order gravity model proposed by Meissner and Olechowski has a graviton mode, a massive spin-two excitation and no scalar mode in a maximally symmetric spacetime; therefore, by choosing the coefficients, we can construct a Lagrangian for `critical gravity' from higher order terms of curvatures in higher dimensions. We also give a comment on construction of the theory with multi-criticality in higher order gravities.

PHYSICAL PROPERTIES, STAR FORMATION, AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN BALMER BREAK GALAXIES AT 0 <z< 1

We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-AGN diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to MIR Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx) and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, 2 (5%) composite galaxies and 3 (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, 3 AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. Furthermore, the relationship between SFR surface density (\Sigma_{SFR}) and stellar mass surface density per time unit (\Sigma_{M_{\ast}/\tau}) as a function of redshift was investigated using the [OII] \lambda3727, 3729, H\alpha \lambda6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and SSFR versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder galaxies and for a given color the SSFR is larger for higher redshift galaxies.

On string theory on [formula omitted] with mixed 3-form flux: Tree-level S-matrix

We consider superstring theory on AdS3×S3×T4 supported by a combination of RR and NSNS 3-form fluxes (with parameter of the NSNS 3-form q). This theory interpolates between the pure RR flux model (q=0) whose spectrum is expected to be described by a (thermodynamic) Bethe ansatz and the pure NSNS flux model (q=1) which is described by the supersymmetric extension of the SL(2,R)×SU(2) WZW model. As a first step towards the solution of this integrable theory for generic value of q we compute the corresponding tree-level S-matrix for massive BMN-type excitations. We find that this S-matrix has a surprisingly simple dependence on q: the diagonal amplitudes have exactly the same structure as in the q=0 case but with the BMN dispersion relation e2=p2+1 replaced by the one with shifted momentum and mass, e2=(p±q)2+1−q2. The off-diagonal amplitudes are then determined from the classical Yang–Baxter equation. We also construct the Pohlmeyer-reduced model corresponding to this superstring theory and find that it depends on q only through the rescaled mass parameter, μ→1−q2μ, implying that its relativistic S-matrix is q-independent.