880 research outputs found
Evaporation of Schwarzschild Black Holes in Matrix Theory
Recently, in collaboration with Susskind, we proposed a model of
Schwarzschild black holes in Matrix theory. A large Schwarzschild black hole is
described by a metastable bound state of a large number of D0-branes which are
held together by a background, whose structure has so far been understood only
in 8 and 11 dimensions. The Hawking radiation proceeds by emission of small
clusters of D0-branes. We estimate the Hawking rate in the Matrix theory model
of Schwarzschild black holes and find agreement with the semiclassical rate up
to an undetermined numerical coefficient of order 1.Comment: 9 pages, harvma
D-brane recoil
It is shown that there are logarithmic operators in D-brane backgrounds that
lead to infrared divergences in open string loop amplitudes. These divergences
can be cancelled by changing the closed string background by operators that
correspond to the D-brane moving with constant velocity after some instant in
time, since it is precisely such operators that give rise to the appropriate
ultraviolet divergences in the closed string channel.Comment: Plain TeX, 5 page
Inverse Seesaw Neutrino Mass from Lepton Triplets in the U(1)_Sigma Model
The inverse seesaw mechanism of neutrino mass, i.e. m_nu =
(m_D^2/m_N^2)epsilon_L where epsilon_L is small, is discussed in the context of
the U(1)_Sigma model. This is a gauge extension of the Standard Model of
particle interactions with lepton triplets (Sigma^+,Sigma^),Sigma^-) as (Type
III) seesaw anchors for obtaining small Majorana neutrino masses.Comment: 7 pages, no figur
Renormalisation of the Fayet-Iliopoulos D-term
We consider the renormalisation of the Fayet-Iliopoulos D-term in a
softly-broken Abelian supersymmetric theory. We show that there exists (at
least through three loops) a renormalisation group invariant trajectory for the
coefficient of the D-term, corresponding to the conformal anomaly solution for
the soft masses and couplings.Comment: 11 pages, TeX, Uses Harvmac (big). References added, minor
corrections (including a sign error for the zeta(3) terms), and discussion of
scheme dependence corrected and amplifie
Schwarzchild Black Holes in Matrix Theory II
We present a crude Matrix Theory model for Schwarzchild black holes in
uncompactified dimension greater than . The model accounts for the size,
entropy, and long range state interactions of black holes. The key feature of
the model is a Boltzmann gas of D0 branes, a concept which depends on certain
qualitative features of Matrix Theory which have not previously been utilized
in studies of black holes.Comment: 20 pages,harvmac,big, Some Typos corrected, 1 reference adde
Beyond Conformal Field Theory
This is an account of some recent work done with H. S. La [1] [2], based ultimately on the work of Fischler and Susskind [3] and Polchinski [4]
Electromagnetic Contributions to the Schiff Moment
The Schiff moment, \smij, is a parity and time reversal violating
fermion-fermion coupling. The nucleus-electron Schiff moment generically gives
the most important contribution to the electric dipole moments of atoms and
molecules with zero net intrinsic electronic spin and nuclear spin . Here, the electromagnetic contribution to the Schiff moment, \emij, is
considered. For a nucleon, the leading chirally violating contribution to this
interaction is calculable in the chiral limit in terms of the parity and time
reversal violating pion-nucleon coupling. For the Schiff moment of heavy
nuclei, this chiral contribution is somewhat smaller than the finite size
effect discussed previously in the literature.Comment: 7 pages, 1 figure (not included), Tex file, requires phyzzx, preprint
SCIPP 93/4
Renormalization of the Fayet-Iliopoulos Term in Softly Broken SUSY Gauge Theories
It is shown that renormalization of the Fayet-Iliopoulos term in a softly
broken SUSY gauge theory, in full analogy with all the other soft terms
renormalizations, is completely defined in a rigid or an unbroken theory.
However, contrary to the other soft renormalizations, there is no simple
differential operator that acts on the renormalization functions of a rigid
theory and allows one to get the renormalization of the F-I term. One needs an
analysis of the superfield diagrams and some additional diagram calculations in
components. The method is illustrated by the four loop calculation of some part
of renormalization proportional to the soft scalar masses and the soft triple
couplings.Comment: Latex2e, 14 pages, uses axodraw.sty. References adde
The issue of Dark Energy in String Theory
Recent astrophysical observations, pertaining to either high-redshift
supernovae or cosmic microwave background temperature fluctuations, as those
measured recently by the WMAP satellite, provide us with data of unprecedented
accuracy, pointing towards two (related) facts: (i) our Universe is accelerated
at present, and (ii) more than 70 % of its energy content consists of an
unknown substance, termed dark energy, which is believed responsible for its
current acceleration. Both of these facts are a challenge to String theory. In
this review I outline briefly the challenges, the problems and possible avenues
for research towards a resolution of the Dark Energy issue in string theory.Comment: Based on Invited lecture at the ``Third Aegean Summer School on: The
Invisible Universe: Dark matter and Dark energy'', Karfas, Chios Island
(Greece) September 26-October 1 200
Effective Action and Phase Structure of Multi-Layer Sine-Gordon Type Models
We analyze the effective action and the phase structure of N-layer
sine-Gordon type models, generalizing the results obtained for the two-layer
sine-Gordon model found in [I. Nandori, S. Nagy, K. Sailer and U. D.
Jentschura, Nucl. Phys. B725, 467-492 (2005)]. Besides the obvious field
theoretical interest, the layered sine-Gordon model has been used to describe
the vortex properties of high transition temperature superconductors, and the
extension of the previous analysis to a general N-layer model is necessary for
a description of the critical behaviour of vortices in realistic multi-layer
systems. The distinction of the Lagrangians in terms of mass eigenvalues is
found to be the decisive parameter with respect to the phase structure of the
N-layer models, with neighbouring layers being coupled by quadratic terms in
the field variables. By a suitable rotation of the field variables, we identify
the periodic modes (without explicit mass terms) in the N-layer structure,
calculate the effective action and determine their Kosterlitz-Thouless type
phase transitions to occur at a coupling parameter \beta^2_{c} = 8 N \pi, where
N is the number of layers (or flavours in terms of the multi-flavour Schwinger
model).Comment: 15 page
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