47 research outputs found
Non-relativistic CFT and Semi-classical Strings
We study different features of 3D non-relativistic CFT using gravity
description. As the corresponding gravity solution can be embedded into the
type IIB string theory, we study semi-classical closed/open strings in this
background. In particular we consider folded rotating and circular pulsating
closed strings where we find the anomalous dimension of the dual operators as a
function of their quantum numbers. We also consider moving open strings in this
background which can be used to compute the drag force. In particular we find
that for slowly moving particles, the energy is lost exponentially and the
characteristic time is given in terms of the temperature, while for fast moving
particles the energy loss goes as inverse of the time and the characteristic
time is independent of the temperature.Comment: 20 pages, Latex file; V2: typos corrected, ref. adde
Black holes in asymptotically Lifshitz spacetime
A model of 3+1 dimensional gravity with negative cosmological constant
coupled to abelian gauge fields has been proposed as a gravity dual for
Lifshitz like critical phenomena in 2+1 dimensions. The finite temperature
behavior is described by black holes that are asymptotic to the Lifshitz fixed
point geometry. There is a one-parameter family of charged black holes, where
the magnitude of the charge is uniquely determined by the black hole area.
These black holes are thermodynamically stable and become extremal in the limit
of vanishing size. The theory also has a discrete spectrum of localized objects
described by non-singular spacetime geometries. The finite temperature behavior
of Wilson loops is reminiscent of strongly coupled gauge theories in 3+1
dimensions, including screening at large distances.Comment: 19 pages, 15 figures in jpeg format, v2: added referenc
NR duals in M-theory
We extend the search for supergravity solution duals of non-relativistic
CFTs to supergravity. We consider the internal space to be an
bundle over a product base: and . For
purely M-theoretic , we find only magnetic fluxes preserving
two supersymmetries. is far richer admitting in addition to
magnetic fluxes, various non-trivial electric fluxes which break all
supersymmetry.Comment: 18 pages, Minor corrections and added reference
Families of IIB duals for nonrelativistic CFTs
We show that the recent string theory embedding of a spacetime with
nonrelativistic Schrodinger symmetry can be generalised to a twenty one
dimensional family of solutions with that symmetry. Our solutions include IIB
backgrounds with no three form flux turned on, and arise as near horizon limits
of branewave spacetimes. We show that there is a hypersurface in the space of
these theories where an instability appears in the gravitational description,
indicating a phase transition in the nonrelativistic field theory dual. We also
present simple embeddings of duals for nonrelativistic critical points where
the dynamical critical exponent can take many values z \neq 2.Comment: 1+25 pages. References adde
Coset Construction for Duals of Non-relativistic CFTs
We systematically analyze backgrounds that are holographic duals to
non-relativistic CFTs, by constructing them as cosets of the Schrodinger group
and variants thereof. These cosets G/H are generically non-reductive and we
discuss in generality how a metric on such spaces can be determined from a
non-degenerate H-invariant symmetric two-form. Applying this to the d=2
Schrodinger algebra, we reproduce the five-dimensional backgrounds proposed as
duals of fermions at unitarity, and under reasonable physical assumptions, we
demonstrate uniqueness of this background. The proposed gravity dual of the
Lifshitz fixed-point, for which Galileian symmetry is absent, also fits into
this organizational scheme and uniqueness of this background can also be shown.Comment: 12 pages; v2: typos corrected, references adde
Ultrafast carrier relaxation in GaN, In_(0.05)Ga_(0.95)N and an In_(0.05)Ga_(0.95)/In_(0.15)Ga_(0.85)N Multiple Quantum Well
Room temperature, wavelength non-degenerate ultrafast pump/probe measurements
were performed on GaN and InGaN epilayers and an InGaN multiple quantum well
structure. Carrier relaxation dynamics were investigated as a function of
excitation wavelength and intensity. Spectrally-resolved sub-picosecond
relaxation due to carrier redistribution and QW capture was found to depend
sensitively on the wavelength of pump excitation. Moreover, for pump
intensities above a threshold of 100 microJ/cm2, all samples demonstrated an
additional emission feature arising from stimulated emission (SE). SE is
evidenced as accelerated relaxation (< 10 ps) in the pump-probe data,
fundamentally altering the re-distribution of carriers. Once SE and carrier
redistribution is completed, a slower relaxation of up to 1 ns for GaN and
InGaN epilayers, and 660 ps for the MQW sample, indicates carrier recombination
through spontaneous emission.Comment: submitted to Phys. Rev.
Branes at Quantum Criticality
In this paper we propose new non-relativistic p+1 dimensional theory. This
theory is defined in such a way that the potential term obeys the principle of
detailed balance where the generating action corresponds to p-brane action.
This condition ensures that the norm of the vacuum wave functional of p+1
dimensional theory is equal to the partition function of p-brane theory.Comment: 17 pages, references added, typos fixed,v2. minor change
Geometry of Schroedinger Space-Times, Global Coordinates, and Harmonic Trapping
We study various geometrical aspects of Schroedinger space-times with
dynamical exponent z>1 and compare them with the properties of AdS (z=1). The
Schroedinger metrics are singular for 1<z<2 while the usual Poincare
coordinates are incomplete for z \geq 2. For z=2 we obtain a global coordinate
system and we explain the relations among its geodesic completeness, the choice
of global time, and the harmonic trapping of non-relativistic CFTs. For z>2, we
show that the Schroedinger space-times admit no global timelike Killing
vectors.Comment: 15 pages, v2: some comments and references adde
Non-relativistic Branes
We construct gravitational non-relativistic brane solutions of type IIA/IIB
string theories and M-theory and their near-horizon geometries. The
non-relativistic M2 and M5-brane metrics have Schroedinger symmetries with
dynamical exponent z=3/2 and z=3, respectively, whereas the known D3-brane
solution has z=2. The non-relativistic D-brane, NS5-brane, F-string and KK
monopole metrics have asymptotically space and time translations, space
rotations, Galilean symmetries and a particle number symmetry. We construct two
different gravitational backgrounds of a non-relativistic D1-D5 system, both
having asymptotically Schroedinger symmetry with exponent z=2. We study the
properties of the solutions and their phase diagram.Comment: 24 pages, harvmac; minor corrections, references adde
How to Argue about Health Care
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68919/2/10.1177_107755878704400102.pd