293 research outputs found
Prospects for Observing an Invisibly Decaying Higgs Boson in the t anti-t H Production at the LHC
The prospects for observing an invisibly decaying Higgs boson in the t anti-t
H production at LHC are discussed. An isolated lepton, reconstructed hadronic
top-quark decay, two identified b-jets and large missing transverse energy are
proposed as the final state signature for event selection. Only the Standard
Model backgrounds are taken into account. It is shown that the t anti-t Z, t
anti-t W, b anti-b Z and b anti-b W backgrounds can individually be suppressed
below the signal expectation. The dominant source of background remains the t
anti-t production. The key for observability will be an experimental selection
which allows further suppression of the contributions from the t anti-t events
with one of the top-quarks decaying into a tau lepton. Depending on the details
of the final analysis, an excess of the signal events above the Standard Model
background of about 10% to 100% can be achieved in the mass range m_H= 100-200
GeV.Comment: Final version as accepted by EPJ
Sustainability perspectives: a new methodological approach for quantitative assessment
This paper proposes a new tool to assess sustainability and make the concept
of sustainable development operational. It considers its multi-dimensional
structure combining the information deriving from a selection of relevant
sustainability indicators belonging to economic, social and environmental
pillars. The main novelties of this approach are the modelling framework, a
recursive-dynamic computable general equilibrium used to calculate the trend
of all indicators over time throughout the world, and the aggregation
methodology to reconcile them in one aggregate index to measure overall
sustainability. The former allows capturing the sector and regional
interactions and higher-order effects driven by background assumptions on
relevant variables to depict future scenarios. The latter makes it possible to
compare sustainability performances, under alternative scenarios, across
countries and over time. Main results show that the current sustainability at
world level differs from what the traditional measure of well-being, the GDP,
depicts, highlighting the trade-offs among different components of
sustainability. Moreover, in the next decade a slight decrease in world
sustainability may occur, in spite of an expected increase in world domestic
product. Finally, dedicated policies increase overall sustainability, showing
that social and environmental benefits may be greater than the correlated
economic costs
Densely Entangled Financial Systems
In [1] Zawadoski introduces a banking network model in which the asset and
counter-party risks are treated separately and the banks hedge their assets
risks by appropriate OTC contracts. In his model, each bank has only two
counter-party neighbors, a bank fails due to the counter-party risk only if at
least one of its two neighbors default, and such a counter-party risk is a low
probability event. Informally, the author shows that the banks will hedge their
asset risks by appropriate OTC contracts, and, though it may be socially
optimal to insure against counter-party risk, in equilibrium banks will {\em
not} choose to insure this low probability event.
In this paper, we consider the above model for more general network
topologies, namely when each node has exactly 2r counter-party neighbors for
some integer r>0. We extend the analysis of [1] to show that as the number of
counter-party neighbors increase the probability of counter-party risk also
increases, and in particular the socially optimal solution becomes privately
sustainable when each bank hedges its risk to at least n/2 banks, where n is
the number of banks in the network, i.e., when 2r is at least n/2, banks not
only hedge their asset risk but also hedge its counter-party risk.Comment: to appear in Network Models in Economics and Finance, V. Kalyagin, P.
M. Pardalos and T. M. Rassias (editors), Springer Optimization and Its
Applications series, Springer, 201
Vacuum structure for expanding geometry
We consider gravitational wave modes in the FRW metrics in a de Sitter phase
and show that the state space splits into many unitarily inequivalent
representations of the canonical commutation relations. Non-unitary time
evolution is described as a trajectory in the space of the representations. The
generator of time evolution is related to the entropy operator. The
thermodynamic arrow of time is shown to point in the same direction of the
cosmological arrow of time. The vacuum is a two-mode SU(1,1) squeezed state of
thermo field dynamics. The link between expanding geometry, squeezing and
thermal properties is exhibited.Comment: Latex file, epsfig, 1 figure, 21 page
Quantum fields in disequilibrium: neutral scalar bosons with long-range, inhomogeneous perturbations
Using Schwinger's quantum action principle, dispersion relations are obtained
for neutral scalar mesons interacting with bi-local sources. These relations
are used as the basis of a method for representing the effect of interactions
in the Gaussian approximation to field theory, and it is argued that a marked
inhomogeneity, in space-time dependence of the sources, forces a discrete
spectrum on the field. The development of such a system is characterized by
features commonly associated with chaos and self-organization (localization by
domain or cell formation). The Green functions play the role of an iterative
map in phase space. Stable systems reside at the fixed points of the map. The
present work can be applied to self-interacting theories by choosing suitable
properties for the sources. Rapid transport leads to a second order phase
transition and anomalous dispersion. Finally, it is shown that there is a
compact representation of the non-equilibrium dynamics in terms of generalized
chemical potentials, or equivalently as a pseudo-gauge theory, with an
imaginary charge. This analogy shows, more clearly, how dissipation and entropy
production are related to the source picture and transform a flip-flop like
behaviour between two reservoirs into the Landau problem in a constant
`magnetic field'. A summary of conventions and formalism is provided as a basis
for future work.Comment: 23 pages revte
Renormalization of Poincare Transformations in Hamiltonian Semiclassical Field Theory
Semiclassical Hamiltonian field theory is investigated from the axiomatic
point of view. A notion of a semiclassical state is introduced. An "elementary"
semiclassical state is specified by a set of classical field configuration and
quantum state in this external field. "Composed" semiclassical states viewed as
formal superpositions of "elementary" states are nontrivial only if the Maslov
isotropic condition is satisfied; the inner product of "composed" semiclassical
states is degenerate. The mathematical proof of Poincare invariance of
semiclassical field theory is obtained for "elementary" and "composed"
semiclassical states. The notion of semiclassical field is introduced; its
Poincare invariance is also mathematically proved.Comment: LaTeX, 40 pages; short version of hep-th/010307
The noncommutative degenerate electron gas
The quantum dynamics of nonrelativistic single particle systems involving
noncommutative coordinates, usually referred to as noncommutative quantum
mechanics, has lately been the object of several investigations. In this note
we pursue these studies for the case of multi-particle systems. We use as a
prototype the degenerate electron gas whose dynamics is well known in the
commutative limit. Our central aim here is to understand qualitatively, rather
than quantitatively, the main modifications induced by the presence of
noncommutative coordinates. We shall first see that the noncommutativity
modifies the exchange correlation energy while preserving the electric
neutrality of the model. By employing time-independent perturbation theory
together with the Seiberg-Witten map we show, afterwards, that the ionization
potential is modified by the noncommutativity. It also turns out that the
noncommutative parameter acts as a reference temperature. Hence, the
noncommutativity lifts the degeneracy of the zero temperature electron gas.Comment: 11 pages, to appear in J. Phys. A: Math. Ge
Production of the neutral toppion at the e gamma colliders
In the framework of topcolor-assisted technicolor(TC2) model, we study a
neutral toppion production process in this
paper. Our results show that the production cross section of can reach the level of several tens fb, and over
neutral toppion events can be produced in the planned linear colliders
each year. Therefore, such a toppion production process provides us a unique
chance to detect toppion events and test the TC2 model. On the other hand, the
cross section of is about one order of
magnitude larger than those of some similar processes in SM and MSSM(i.e.,
in SM and in
MSSM). So, we can easily distinguish the neutral toppion from other neutral
Higgs bosons in SM and MSSM.Comment: 12 pages, 4 figures, The paper has been accepted by Phys.Rev.
Much Ado About Leptoquarks: A Comprehensive Analysis
We examine the phenomenological implications of a 200 GeV leptoquark in light
of the recent excess of events at HERA. Given the relative predictions of
events rates in e^+p versus e^-p, we demonstrate that classes of leptoquarks
may be excluded, including those contained in E_6 GUT models. It is shown that
future studies with polarized beams at HERA could reveal the chirality of the
leptoquark fermionic coupling and that given sufficient luminosity in each
e^\pm_{L,R} channel the leptoquark quantum numbers could be determined. The
implications of 200-220 GeV leptoquarks at the Tevatron are examined. While
present Tevatron data most likely excludes vector leptoquarks and leptogluons
in this mass region, it does allow for scalar leptoquarks. We find that while
leptoquarks have little influence on Drell-Yan production, further studies at
the Main Injector are possible in the single production channel. We investigate
precision electroweak measurements as well as the process e^+e^-\to q\bar q at
LEP II and find they provide no further restrictions on these leptoquark
models. We then ascertain that cross section and polarization asymmetry
measurements at the NLC provide the only direct mechanism to determine the
leptoquark's electroweak quantum numbers. The single production of leptoquarks
in \gamma e collisions by both the backscattered laser and Weisacker-Williams
techniques at the NLC is also discussed. Finally, we demonstrate that we can
obtain successful coupling constant unification in models with leptoquarks,
both with or without supersymmetry. The supersymmetric case requires the GUT
group to be larger than SU(5) such as flipped SU(5)\times U(1)_X.Comment: Corrected single production cross section at Tevatron, updated atomic
parity violation constraints, 55 page
- …