9,271 research outputs found
An existence result for a nonlinear transmission problems
Let and be open bounded subsets of of
class such that the closure of is contained in
. Let be a function in and let
and be continuous functions from to
. By exploiting an argument based on potential theory and on the
Leray-Schauder principle we show that under suitable and completely explicit
conditions on and there exists at least one pair of continuous
functions such that where the last equality is attained in certain weak sense. In a simple
example we show that such a pair of functions is in general
neither unique nor local unique. If instead the fourth condition of the problem
is obtained by a small nonlinear perturbation of a homogeneous linear
condition, then we can prove the existence of at least one classical solution
which is in addition locally unique
Positively charged magneto-excitons in a semiconductor quantum well
A variational calculation of the lower singlet and triplet states of
positively charged excitons (trions) confined to a single quantum well and in
the presence of a perpendicular magnetic field is presented. We study the
dependence of the energy levels and of the binding energy on the well width and
on the magnetic field strength. Our results are compared with the available
experimental data and show a good qualitative and quantitative agreement. A
singlet-triplet crossing is found which for a 200 \AA wide GaAs is predicted to
occur for B = 15 T.Comment: 5 figs. Submitted to PR
Heteropolymers in a Solvent at an Interface
Exact bounds are obtained for the quenched free energy of a polymer with
random hydrophobicities in the presence of an interface separating a polar from
a non polar solvent. The polymer may be ideal or have steric self-interactions.
The bounds allow to prove that a ``neutral'' random polymer is localized near
the interface at any temperature, whereas a ``non-neutral'' chain is shown to
undergo a delocalization transition at a finite temperature. These results are
valid for a quite general a priori probability distribution for both
independent and correlated hydrophobic charges. As a particular case we
consider random AB-copolymers and confirm recent numerical studies.Comment: 4 pages, no figure
Toxines cianobacterials. Part II: Factors ambientals decisius en la producció i l'estabilitat de les microcistines
Higgs Couplings in Composite Models
We study Higgs couplings in the composite Higgs model based on the coset
SO(5)/SO(4). We show that the couplings to gluons and photons are insensitive
to the elementary-composite mixings and thus not affected by light fermionic
resonances. Moreover, at leading order in the mixings the Higgs couplings to
tops and gluons, when normalized to the Standard Model (SM), are equal. These
properties are shown to be direct consequences of the Goldstone symmetry and of
the assumption of partial compositeness. In particular, they are independent of
the details of the elementary-composite couplings and, under the further
assumption of CP invariance, they are also insensitive to derivative
interactions of the Higgs with the composite resonances. We support our
conclusions with an explicit construction where the SM fermions are embedded in
the 14 dimensional representation of SO(5).Comment: 13 pages, 3 figures, 2 tables; v2: small improvements in the
discussion, results unchanged; typos corrected; one reference added. Matches
version submitted to PR
THE IMPACT OF THE NEW ITALIAN EARLY WARNING SYSTEM PROVIDED BY THE IC-CODE ON FAMILY SMES GOVERNANCE
The Early Warning System is intended as an instrument aimed at driving the companies in the identification of the very first signs of crisis. Monitoring the occurring of the crisis is no longer a responsibility of the sole entrepreneur or of the board of directors but other legitimized subjects are identified. The IC-Code sets up new corporate governance rules for a huge number of Italian Family SMEs pretending the introduction of independent control bodies, Board of Statutory Auditors, and/or External Auditor. Some of the suggestions coming from the family business framework seems then to be enforced by law in the Italian context
The Social Appearance Anxiety Scale in Italian adolescent populations: Construct validation and group discrimination in community and clinical eating disorders samples
Anxiety in situations where one’s overall appearance (including body shape) may be negatively evaluated is hypothesized to play a central role in Eating Disorders (EDs) and in their co-occurrence with Social Anxiety Disorder (SAD). Three studies were conducted among community (N = 1995) and clinical (N = 703) ED samples of 11- to 18-year-old Italian girls and boys to (a) evaluate the psychometric qualities and measurement equivalence/invariance (ME/I) of the Social Appearance Anxiety (SAA) Scale (SAAS) and (b) determine to what extent SAA or other situational domains of social anxiety related to EDs distinguish adolescents with an ED only from those with SAD. Results upheld the one-factor structure and ME/I of the SAAS across samples, gender, age categories, and diagnostic status (i.e., ED participants with and without comorbid SAD). The SAAS demonstrated high internal consistency and 3-week test–retest reliability. The strength of the inter-relationships between SAAS and measures of body image, teasing about appearance, ED symptoms, depression, social anxiety, avoidance, and distress, as well as the ability of SAAS to discriminate community adolescents with high and low levels of ED symptoms and community participants from ED participants provided construct validity evidence. Only SAA strongly differentiated adolescents with any ED from those with comorbid SAD (23.2 %). Latent mean comparisons across all study groups were performed and discussed
Excitons and charged excitons in semiconductor quantum wells
A variational calculation of the ground-state energy of neutral excitons and
of positively and negatively charged excitons (trions) confined in a
single-quantum well is presented. We study the dependence of the correlation
energy and of the binding energy on the well width and on the hole mass. The
conditional probability distribution for positively and negatively charged
excitons is obtained, providing information on the correlation and the charge
distribution in the system. A comparison is made with available experimental
data on trion binding energies in GaAs-, ZnSe-, and CdTe-based quantum well
structures, which indicates that trions become localized with decreasing
quantum well width.Comment: 9 pages, 11 figure
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