Searching for the dual of the Maxwell-Chern-Simons model minimally coupled to dynamical U(1) charged matter

The possibility of dual equivalence between the self-dual and the Maxwell-Chern-Simons (MCS) models when the latter is coupled to dynamical, U(1) fermionic charged matter is examined. The proper coupling in the self-dual model is then disclosed using the iterative gauge embedding approach. We found that the self-dual potential needs to couple directly to the Chern-Kernel of the source in order to establish this equivalence besides the need for a self-interaction term to render the matter sector unchanged.Comment: 4 pages, RevTeX, new references, accepted for publication on Phys. Lett.

A Resolution of the Cosmological Singularity with Orientifolds

We propose a new cosmological scenario which resolves the conventional initial singularity problem. The space-time geometry has an unconventional time-like singularity on a lower dimensional hypersurface, with localized energy density. The natural interpretation of this singularity in string theory is that of negative tension branes, for example the orientifolds of type II string theory. Space-time ends at the orientifolds, and it is divided in three regions: a contracting region with a future cosmological horizon; an intermediate region which ends at the orientifols; and an expanding region separated from the intermediate region by a past cosmological horizon. We study the geometry near the singularity of the proposed cosmological scenario in a specific string model. Using D-brane probes we confirm the interpretation of the brane singularity as an orientifold. The boundary conditions on the orientifolds and the past/future transition amplitudes are well defined. Assuming the trivial vacuum in the past, we derive a thermal spectrum in the future.Comment: 1+20 pages, 3 figures; Analogy between orientifolds and de Sitter space in Introduction corrected, refs adde

Low-Energy Brane-World Effective Actions and Partial Supersymmetry Breaking

As part of a programme for the general study of the low-energy implications of supersymmetry breaking in brane-world scenarios, we study the nonlinear realization of supersymmetry which occurs when breaking N=2 to N=1 supergravity. We consider three explicit realizations of this supersymmetry breaking pattern, which correspond to breaking by one brane, by one antibrane or by two (or more) parallel branes. We derive the minimal field content, the effective action and supersymmetry transformation rules for the resulting N=1 theory perturbatively in powers of kappa = 1/M_{Planck}. We show that the way the massive gravitino and spin-1 fields assemble into N=1 multiplets implies the existence of direct brane-brane contact interactions at order O(kappa). This result is contrary to the O(kappa^2) predicted by the sequestering scenario but in agreement with recent work of Anisimov et al. Our low-energy approach is model independent and is a first step towards determining the low-energy implications of more realistic brane models which completely break all supersymmetries.Comment: Latex, 29 Page

Measuring effective electroweak couplings in single top production at the LHC

We study the mechanism of single top production at the LHC in the framework of an effective electroweak Lagrangian, analyzing the sensitivity of different observables to the magnitude of the effective couplings that parametrize new physics beyond the Standard Model. The observables relevant to the distinction between left and right effective couplings involve in practice the measurement of the spin of the top and this can be achieved only indirectly by measuring the angular distribution of its decay products. We show that the presence of effective right-handed couplings implies that the top is not in a pure spin state. A unique spin basis is singled out which allows one to connect top decay products angular distribution with the polarized top differential cross section. We present a complete analytical expression of the differential polarized cross section of the relevant perturbative subprocess including general effective couplings. The mass of the bottom quark, which actually turns out to be more relevant than naively expected, is retained. Finally we analyze different aspects the total cross section relevant to the measurement of new physics through the effective couplings. The above analysis also applies to anti-top production in a straightforward way.Comment: 38 pages, 17 figure

The Equivalence Theorem and Effective Lagrangians

We point out that the equivalence theorem, which relates the amplitude for a process with external longitudinally polarized vector bosons to the amplitude in which the longitudinal vector bosons are replaced by the corresponding pseudo-Goldstone bosons, is not valid for effective Lagrangians. However, a more general formulation of this theorem also holds for effective interactions. The generalized theorem can be utilized to determine the high-energy behaviour of scattering processes just by power counting and to simplify the calculation of the corresponding amplitudes. We apply this method to the phenomenologically most interesting terms describing effective interactions of the electroweak vector and Higgs bosons in order to examine their effects on vector-boson scattering and on vector-boson-pair production in $f\bar{f}$ annihilation. The use of the equivalence theorem in the literature is examined.Comment: 20 pages LaTeX, BI-TP 94/1

Top-quark spin correlation at Linear Colliders with anomalous couplings

We investigate the feasibility of probing anomalous top-quark couplings of $Wtb$, $Z t \bar{t}$, and $\gamma t \bar{t}$ in terms of an effective Lagrangian with dimension-six operators at future $e^+e^-$ linear colliders with a c. m. energy $\sqrt s \sim 500-800$ GeV. We first examine the constraints on these anomalous couplings from the $Z\to b \bar{b}$ data at LEP I and from unitarity considerations. We then consider in detail the effects of anomalous couplings on $t \bar{t}$ spin correlations in the top-pair production and decay with three spin bases: the helicity, beamline and off-diagonal bases. Our results show that the polarized beams are more suitable for exploring the effects of different new operators. For polarized beams, the helicity basis yields the best sensitivity.Comment: 23 pages, 10 figures, references adde

Groundwater resources in the Indo-Gangetic Basin : resilience to climate change and abstraction

Groundwater within the Indo‐Gangetic Basin (IGB) alluvial aquifer system forms one of the world’s most important and heavily exploited reservoirs of freshwater. In this study we have examined the groundwater system through the lens of its resilience to change – both from the impact of climate change and increases in abstraction. This has led to the development of a series of new maps for the IGB aquifer, building on existing datasets held in Pakistan, India, Nepal and Bangladesh, a review of approximately 500 reports and papers, and three targeted field studies on under‐researched topics within the region. The major findings of the study are described below. The IGB groundwater system 1. The IGB alluvial aquifer system comprises a large volume of heterogeneous unconsolidated sediment in a complex environmental setting. Annual rainfall varies from 2000mm in the Bengal basin, and the system is dissected by the major river systems of the Indus, Ganges and Brahmaputra. The groundwater system has been modified by the introduction of large scale canal irrigation schemes using water from the Indus and Ganges since the 19th and early 20th centuries. 2. High yielding tubewells can be sustained in most parts of the alluvial aquifer system; permeability is often in the range of 10 – 60 m/d and specific yield (the drainable porosity) varies from 5 – 20%, making it highly productive. 3. High salinity and elevated arsenic concentrations exist in parts of the basin limiting the usefulness of the groundwater resource. Saline water predominates in the Lower Indus, and near to the coast in the Bengal Delta, and is also a major concern in the Middle Ganges and Upper Ganges (covering much of the Punjab Region in Pakistan, southern Punjab, Haryana and parts of Uttar Pradesh in India). Arsenic severely impacts the development of shallow groundwater in the fluvial influenced deltaic area of the Bengal Basin. 4. Recharge to the IGB aquifer system is substantial and dynamic, controlled by monsoonal rainfall, leakage from canals, river infiltration and irrigation returns. Recharge from rainfall can occur even with low annual rainfall (350 mm) and appears to dominate where rainfall is higher (> 750 mm). Canal leakage is also highly significant and constitutes the largest proportion of groundwater recharge in the drier parts of the aquifer, partially mitigating the effects of abstraction on groundwater storage. 5. Deep groundwater (>150 m) in the Bengal basin has strategic value for water supply, health and economic development. Excessive abstraction poses a greater threat to the quality of this deep groundwater than climate change. Heavy pumping may induce the downward migration of arsenic in parts of Bangladesh, and of saline water in coastal regions, but field evidence and modelling both suggest that deep groundwater abstraction for public water supply in southern Bangladesh is in general secure against widespread ingress of arsenic and saline water for at least 100 years

Constraints on Masses of Charged PGBs in Technicolor Model from Decay b→sγ b \to s \gamma

In this paper we calculate the contributions to the branching ratio of $B\to X_s \gamma$ from the charged Pseudo-Goldstone bosons appeared in one generation Technicolor model. The current $CLEO$ experimental results can eliminate large part of the parameter space in the $m(P^\pm) - m(P_8^\pm)$ plane, and specifically, one can put a strong lower bound on the masses of color octet charged PGBs $P_8^\pm$: $m(P^{\pm}_8) > 400\;GeV$ at $90\%C.L$ for free $m(P^{\pm})$.Comment: 9 pages, 3 figures(uuencoded), Minor changes(Type error), to appear in Phys. Rev.

Invisible Axions and Large-Radius Compactifications

We study some of the novel effects that arise when the QCD axion is placed in the ``bulk'' of large extra spacetime dimensions. First, we find that the mass of the axion can become independent of the energy scale associated with the breaking of the Peccei-Quinn symmetry. This implies that the mass of the axion can be adjusted independently of its couplings to ordinary matter, thereby providing a new method of rendering the axion invisible. Second, we discuss the new phenomenon of laboratory axion oscillations (analogous to neutrino oscillations), and show that these oscillations cause laboratory axions to ``decohere'' extremely rapidly as a result of Kaluza-Klein mixing. This decoherence may also be a contributing factor to axion invisibility. Third, we discuss the role of Kaluza-Klein axions in axion-mediated processes and decays, and propose several experimental tests of the higher-dimensional nature of the axion. Finally, we show that under certain circumstances, the presence of an infinite tower of Kaluza-Klein axion modes can significantly accelerate the dissipation of the energy associated with cosmological relic axion oscillations, thereby enabling the Peccei-Quinn symmetry-breaking scale to exceed the usual four-dimensional relic oscillation bounds. Together, these ideas therefore provide new ways of obtaining an ``invisible'' axion within the context of higher-dimensional theories with large-radius compactifications.Comment: 43 pages, LaTeX, 6 figure