953 research outputs found
Modular Invariance, Finiteness, and Misaligned Supersymmetry: New Constraints on the Numbers of Physical String States
We investigate the generic distribution of bosonic and fermionic states at
all mass levels in non-supersymmetric string theories, and find that a hidden
``misaligned supersymmetry'' must always appear in the string spectrum. We show
that this misaligned supersymmetry is ultimately responsible for the finiteness
of string amplitudes in the absence of full spacetime supersymmetry, and
therefore the existence of misaligned supersymmetry provides a natural
constraint on the degree to which spacetime supersymmetry can be broken in
string theory without destroying the finiteness of string amplitudes.
Misaligned supersymmetry also explains how the requirements of modular
invariance and absence of physical tachyons generically affect the distribution
of states throughout the string spectrum, and implicitly furnishes a
two-variable generalization of some well-known results in the theory of modular
functions.Comment: standard LaTeX; 55 pages, 4 figures. (Note: This replaced version
matches the version which was published in Nuclear Physics B.
A Search for Instantons at HERA
A search for QCD instanton (I) induced events in deep-inelastic scattering
(DIS) at HERA is presented in the kinematic range of low x and low Q^2. After
cutting into three characteristic variables for I-induced events yielding a
maximum suppression of standard DIS background to the 0.1% level while still
preserving 10% of the I-induced events, 549 data events are found while
363^{+22}_{-26} (CDM) and 435^{+36}_{-22} (MEPS) standard DIS events are
expected. More events than expected by the standard DIS Monte Carlo models are
found in the data. However, the systematic uncertainty between the two
different models is of the order of the expected signal, so that a discovery of
instantons can not be claimed. An outlook is given on the prospect to search
for QCD instanton events using a discriminant based on range searching in the
kinematical region Q^2\gtrsim100\GeV^2 where the I-theory makes safer
predictions and the QCD Monte Carlos are expected to better describe the
inclusive data.Comment: Invited talk given at the Ringberg Workshop on HERA Physics on June
19th, 2001 on behalf of the H1 collaboratio
I2PA, U-prove, and Idemix: An Evaluation of Memory Usage and Computing Time Efficiency in an IoT Context
The Internet of Things (IoT), in spite of its innumerable advantages, brings
many challenges namely issues about users' privacy preservation and constraints
about lightweight cryptography. Lightweight cryptography is of capital
importance since IoT devices are qualified to be resource-constrained. To
address these challenges, several Attribute-Based Credentials (ABC) schemes
have been designed including I2PA, U-prove, and Idemix. Even though these
schemes have very strong cryptographic bases, their performance in
resource-constrained devices is a question that deserves special attention.
This paper aims to conduct a performance evaluation of these schemes on
issuance and verification protocols regarding memory usage and computing time.
Recorded results show that both I2PA and U-prove present very interesting
results regarding memory usage and computing time while Idemix presents very
low performance with regard to computing time
Exact Superpotentials from Matrix Models
Dijkgraaf and Vafa (DV) have conjectured that the exact superpotential for a
large class of N=1 SUSY gauge theories can be extracted from the planar limit
of a certain holomorphic matrix integral. We test their proposal against
existing knowledge for a family of deformations of N=4 SUSY Yang-Mills theory
involving an arbitrary polynomial superpotential for one of the three adjoint
chiral superfields. Specifically, we compare the DV prediction for these models
with earlier results based on the connection between SUSY gauge theories and
integrable systems. We find complete agreement between the two approaches. In
particular we show how the DV proposal allows the extraction of the exact
eigenvalues of the adjoint scalar in the confining vacuum and hence computes
all related condensates of the finite-N gauge theory. We extend these results
to include Leigh-Strassler deformations of the N=4 theory.Comment: 28 pages, 1 figure, latex with JHEP.cls, replaced with typos
corrected and one clarifying commen
Probing F-theory With Multiple Branes
We study multiple 3-branes on an F theory orientifold. The world-volume
theory of the 3-branes is d=4, N=2 Sp(2k) gauge theory with an antisymmetric
tensor and four flavors of matter in the fundamental. The solution of this
gauge theory is found for vanishing bare mass of the antisymmetric tensor
matter, and massive fundamental matter. The integrable system underlying this
theory is constructed.Comment: 9 pages, harvma
On rationality of the intersection points of a line with a plane quartic
We study the rationality of the intersection points of certain lines and
smooth plane quartics C defined over F_q. For q \geq 127, we prove the
existence of a line such that the intersection points with C are all rational.
Using another approach, we further prove the existence of a tangent line with
the same property as soon as the characteristic of F_q is different from 2 and
q \geq 66^2+1. Finally, we study the probability of the existence of a rational
flex on C and exhibit a curious behavior when the characteristic of F_q is
equal to 3.Comment: 17 pages. Theorem 2 now includes the characteristic 2 case;
Conjecture 1 from the previous version is proved wron
Efficient algorithms for pairing-based cryptosystems
We describe fast new algorithms to implement recent cryptosystems based on the Tate pairing. In particular, our techniques improve pairing evaluation speed by a factor of about 55 compared to previously known methods in characteristic 3, and attain performance comparable
to that of RSA in larger characteristics.We also propose faster algorithms for scalar multiplication in characteristic 3 and square root extraction
over Fpm, the latter technique being also useful in contexts other than that of pairing-based cryptography
Influência da concentração de NaCl e pH na extração de ricina em torta de mamona (Ricinus communis L.) e sua caracterização por eletroforese.
A mamoneira (Ricinus communis L.) é uma oleaginosa de alto valor econômico pelo fato de apresentar um mercado bem definido para o óleo extraído de suas sementes. A torta, que é um resíduo desta extração, se destaca pelo alto teor em proteínas. Dentre as proteínas encontradas na torta destaca-se a ricina, uma citotoxina, que inviabiliza sua utilização como fonte protéica alternativa para alimentação animal. O presente trabalho tem como objetivo identificar um melhor tratamento experimental para a extração de ricina da torta de mamona, visando futuros estudos de perda de integridade da ricina, o que garantiria a inocuidade do produto. Para tanto, buscou-se identificar a solução de maior capacidade de extração de proteínas, empregando a metodologia de superfície de resposta. Um delineamento composto central rotacional foi elaborado a fim de verificar o melhor pH e concentração de NaCl para a extração. Dos cinco diferentes valores de pH (4,0; 4,6; 6,0; 7,4; 8,0) e concentração de NaCl (0,0M; 0,3M; 1,0M; 1,7M; 2,0M) utilizados, o tratamento associando fosfato de potássio 0,2M/NaCl 1,7M pH 7,4 foi escolhido como o melhor. A concentração de proteína extraída neste tratamento chegou a valores quatro vezes maiores que o encontrado no de mínima extração de proteína. Pela evidenciação do gel de eletroforese não houve extração preferencial de ricina nos tratamentos testados, entretanto etapas de purificação usando diálise e precipitação com sulfato de amônio, permitiram uma evidenciação melhor das duas cadeias polipeptídicas de ricina
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