1,902 research outputs found
Gauge Instantons from Open Strings
In this contribution we describe how to obtain instanton effects in four
dimensional gauge theories by computing string scattering amplitudes in
D3/D(-1) brane systems. In particular we show that the disks with mixed
boundary conditions, which are typical of the D3/D(-1) system, are the sources
for the classical instanton solution.Comment: 7 pages, 2 figures, Contribution to the proceedings of the 36th
International Symposium Ahrenshoop, Berlin, Germany, 26-30 August 200
Direct and long-lasting effects elicited by repeated drug administration on 50-kHz ultrasonic vocalizations are regulated differently: Implications for the study of the affective properties of drugs of abuse
Several studies suggest that 50-kHz ultrasonic vocalizations (USVs) may indicate a positive affective state in rats, and these vocalizations are increasingly being used to investigate the properties of psychoactive drugs. Previous studies, however, have focused on dopaminergic psychostimulants and morphine, whereas little is known about how other drugs modulate 50-kHz USVs. To further elucidate the neuropharmacology of 50-kHz USVs, the present study characterized the direct and long-lasting effects of different drugs of abuse, by measuring the number of 50-kHz USVs and their 'trill' subtype emitted by adult male rats. Rats received repeated administrations of amphetamine (2 mg/kg, i.p.), 3,4-methylenedioxymethamphetamine (MDMA, 7.5 mg/kg, i.p.), morphine (7.5 mg/kg, s.c.), or nicotine (0.4 mg/kg, s.c.), on either consecutive or alternate days (five administrations in total) in a novel environment. Seven days later, rats were re-exposed to the drug-paired environment, subjected to USVs recording, and then challenged with the same drug. Finally, 7 d after the challenge, rats were repeatedly exposed to the drug-paired environment and vocalizations were measured. Amphetamine was the only drug to stimulate 50-kHz USVs and 'trill' subtype emission during administration and challenge. Conversely, all rats emitted 50-kHz USVs when re-exposed to the test cage, and this effect was most marked in morphine-treated rats, and less evident in nicotine-treated rats. This study demonstrates that the direct and long-lasting effects of drugs on 50-kHz USVs are regulated differently, providing a better understanding of the usefulness of these vocalizations in the study of psychoactive drugs
Stable non-BPS D-branes of type I
We review the boundary state description of the non-BPS D-branes in the type
I string theory and show that the only stable configurations are the D-particle
and the D-instanton. We also compute the gauge and gravitational interactions
of the non-BPS D-particles and compare them with the interactions of the dual
non-BPS particles of the heterotic string finding complete agreement. In this
way we provide further dynamical evidence of the heterotic/type I duality.Comment: 8 pages, 1 figure.eps, JHEP.cls, talk given by A. Lerda at the TMR
Conference "Quantum aspects of gauge theories, supersymmetry and
unification", Paris, September 199
Il Syria vote e la palingenesi del parlamentarismo britannico
Nel primo scorcio del nuovo millennio è andata sviluppandosi, nel Regno Unito, una nuova convenzione costituzionale che ha inciso profondamente sullo storico potere di prerogativa dell'esecutivo relativo al dispiegamento delle forze armate in scenari di conflitto (power to deploy troops overseas). In base alla nuova convenzione costituzionale, registrata anche nel Cabinet Manual del 2011, ogni "azione militare significativa" decisa dal Governo britannico deve essere sottoposta a un dibattito parlamentare preventivo, salvo che ricorra una situazione di urgenza. Si è così affermata una regola che prescrive un "full debate" e un voto di approvazione preventiva della Camera dei comuni avente ad oggetto un'apposita "emendable motion" del Governo relativa all'uso della forza militare. Il c.d. Syria vote del 2013 e le sue conseguenze rappresentano un’importante occasione per il consolidamento della nuova convenzione costituzionale, che ha riequilibrando i rapporti tra Governo e Parlamento in questo delicato ambito materiale. Trattandosi della progressiva maturazione di una Convention of the Constitution di portata potenzialmente rivoluzionaria, la vicenda merita un’approfondita analisi anche sul piano cronachistico. Il tema è di estrema rilevanza anzitutto con riferimento all'evoluzione del sistema di governo del Regno Unito, intrecciandosi con l'esperienza del governo di coalizione nato nel 2010 e con la valorizzazione del ruolo del Parlamento avvenuta in quel frangente. Esso rileva inoltre nell'ambito dell'analisi comparativa dei c.d. poteri costituzionali di guerra, in relazione ad altre esperienze di democrazia maggioritaria
Modular anomaly equation, heat kernel and S-duality in N=2 theories
We investigate epsilon-deformed N=2 superconformal gauge theories in four
dimensions, focusing on the N=2* and Nf=4 SU(2) cases. We show how the modular
anomaly equation obeyed by the deformed prepotential can be efficiently used to
derive its non-perturbative expression starting from the perturbative one. We
also show that the modular anomaly equation implies that S-duality is
implemented by means of an exact Fourier transform even for arbitrary values of
the deformation parameters, and then we argue that it is possible,
perturbatively in the deformation, to choose appropriate variables such that it
reduces to a Legendre transform.Comment: 30 pages, LeTeX2e. V2: references added, appendix B expanded, a few
typos correcte
The extended conformal theory of Luttinger systems
We describe the recently introduced method of algebraic bosonization of the
-dimensional Luttinger systems by discussing in detail the specific case
of the Calogero-Sutherland model, and mentioning the hard-core Bose gas. We
also compare our findings with the exact Bethe Ansatz results.Comment: 9 pages, plain Latex file, ,based on a talk given by S. Sciuto at the
II International Sakharov Conference on Physics, Moscow, Russia, 20-24 May 9
S-duality and the prepotential in N=2* theories (I): the ADE algebras
The prepotential of N=2* supersymmetric theories with unitary gauge groups in
an Omega-background satisfies a modular anomaly equation that can be
recursively solved order by order in an expansion for small mass. By requiring
that S-duality acts on the prepotential as a Fourier transform we generalise
this result to N=2* theories with gauge algebras of the D and E type and show
that their prepotentials can be written in terms of quasi-modular forms of
SL(2,Z). The results are checked against microscopic multi-instanton calculus
based on localization for the A and D series and reproduce the known
1-instanton prepotential of the pure N=2 theories for any gauge group of ADE
type. Our results can also be used to obtain the multi-instanton terms in the
exceptional theories for which the microscopic instanton calculus and the ADHM
construction are not available.Comment: 33 pages, LaTeX2e, added references, version to be published in JHE
Shaping a high-mass star-forming cluster through stellar feedback. The case of the NGC 7538 IRS 1-3 complex
Context: NGC 7538 IRS 1-3 is a high-mass star-forming cluster with several
detected dust cores, infrared sources, (ultra)compact H regions,
molecular outflows, and masers. In such a complex environment, important
interactions and feedback among the embedded objects are expected to play a
major role in the evolution of the region. Aims: We study the dust, kinematic,
and polarimetric properties of the NGC 7538 IRS 1-3 region to investigate the
role of the different forces interplaying in the formation and evolution of
high-mass star-forming clusters. Methods: We perform SMA high angular
resolution observations at 880 m with the compact configuration. We
develop the RATPACKS code to generate synthetic velocity cubes from models of
choice to be compared to the observational data. We develop the "mass balance"
analysis to quantify the stability against gravitational collapse accounting
for all the energetics at core scales. Results: We detect 14 dust cores from
3.5 to 37 arranged in two larger scale structures: a
central bar and a filamentary spiral arm. The spiral arm presents large scale
velocity gradients in HCO 4-3 and CO 3-2, and magnetic field
segments well aligned to the dust main axis. The velocity gradient is well
reproduced by a spiral arm expanding at 9 km s with respect to the
central core MM1, which is known to power a large precessing outflow. The
energy of the outflow is comparable with the spiral arm kinetic energy, which
is dominant over gravitational and magnetic energies. In addition, the
dynamical ages of the outflow and spiral arm are comparable. ... (Full abstract
in the pdf version)Comment: 15 pages, 9 figures, 4 tables. Accepted for publication in A&
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