



01030nas a2200157   4500008004100000245006700041210006700108260001400175520054300189100001900732700002900751700001700780700001900797700001900816856003700835       2020                        eng d00aStudying viral populations with tools from quantum spin chains0 aStudying viral populations with tools from quantum spin chains  c3/24/20203 a<p>We study Eigen&#39;s model of quasi-species, characterized by sequences that replicate with a specified fitness and mutate independently at single sites. The evolution of the population vector in time is then closely related to that of quantum spins in imaginary time. We employ multiple perspectives and tools from interacting quantum systems to examine growth and collapse of realistic viral populations, specifically certain HIV proteins. All approaches used, including the simplest perturbation theory, give consistent results.</p>1 aShivam, Saumya1 aBaldwin, Christopher, L.1 aBarton, John1 aKardar, Mehran1 aSondhi, S., L.  uhttps://arxiv.org/abs/2003.1066801255nas a2200157   4500008004100000245006900041210006900110260001500179300001100194490000700205520078100212100002700993700002201020700001901042856003601061       2016                        eng d00aFlight of a heavy particle nonlinearly coupled to a quantum bath0 aFlight of a heavy particle nonlinearly coupled to a quantum bath  c2016/01/28  a0143090 v933 a  Fluctuation and dissipation are by-products of coupling to the `environment.'
The Caldeira-Leggett model, a successful paradigm of quantum Brownian motion,
views the environment as a collection of harmonic oscillators linearly coupled
to the system. However, symmetry considerations may forbid a linear coupling,
e.g. for a neutral particle in quantum electrodynamics. We argue that nonlinear
couplings can lead to a fundamentally different behavior. Specifically, we
consider a heavy particle quadratically coupled to quantum fluctuations of the
bath. In one dimension the particle undergoes anomalous diffusion, unfolding as
a power-law distribution in space, reminiscent of L\'{e}vy flights. We suggest
condensed matter analogs where similar effects may arise.
1 aMaghrebi, Mohammad, F.1 aKrüger, Matthias1 aKardar, Mehran  uhttp://arxiv.org/abs/1508.0058201828nas a2200145   4500008004100000245015000041210006900191260001400260490000700274520129600281100002701577700002201604700001901626856003701645       2014                        eng d00aNonequilibrium quantum fluctuations of a dispersive medium: Spontaneous  emission, photon statistics, entropy generation, and stochastic motion
0 aNonequilibrium quantum fluctuations of a dispersive medium Spont  c2014/7/160 v903 a  We study the implications of quantum fluctuations of a dispersive medium,
under steady rotation, either in or out of thermal equilibrium with its
environment. A rotating object exhibits a quantum instability by dissipating
its mechanical motion via spontaneous emission of photons, as well as internal
heat generation. Universal relations are derived for the radiated energy and
angular momentum as trace formulas involving the object's scattering matrix. We
also compute the quantum noise by deriving the full statistics of the radiated
photons out of thermal and/or dynamic equilibrium. The (entanglement) entropy
generation is quantified, and the total entropy is shown to be always
increasing. Furthermore, we derive a Fokker-Planck equation governing the
stochastic angular motion resulting from the fluctuating back-reaction
frictional torque. As a result, we find a quantum limit on the uncertainty of
the object's angular velocity in steady rotation. Finally, we show in some
detail that a rotating object drags nearby objects, making them spin parallel
to its axis of rotation. A scalar toy model is introduced in the first part to
simplify the technicalities and ease the conceptual complexities; a detailed
discussion of quantum electrodynamics is presented in the second part.
1 aMaghrebi, Mohammad, F.1 aJaffe, Robert, L.1 aKardar, Mehran  uhttp://arxiv.org/abs/1401.0701v101052nas a2200145   4500008004100000245005700041210005600098260001500154490000700169520062400176100002700800700002300827700001900850856003700869       2013                        eng d00aQuantum Cherenkov Radiation and Non-contact Friction0 aQuantum Cherenkov Radiation and Noncontact Friction  c2013/10/210 v883 a  We present a number of arguments to demonstrate that a quantum analog of
Cherenkov effect occurs when two dispersive objects are in relative motion.
Specifically we show that two semi-infinite plates experience friction beyond a
threshold velocity which, in their center-of-mass frame, is the phase speed of
light within their medium. The loss in mechanical energy is radiated away
through the plates before getting fully absorbed in the form of heat. By
deriving various correlation functions inside and outside the two plates, we
explicitly compute the radiation, and discuss its dependence on the reference
frame.
1 aMaghrebi, Mohammad, F.1 aGolestanian, Ramin1 aKardar, Mehran  uhttp://arxiv.org/abs/1304.4909v201136nas a2200145   4500008004100000245005800041210005600099260001300155490000700168520070900175100002700884700002300911700001900934856003700953       2013                        eng d00aA Scattering Approach to the Dynamical Casimir Effect0 aScattering Approach to the Dynamical Casimir Effect  c2013/1/70 v873 a  We develop a unified scattering approach to dynamical Casimir problems which
can be applied to both accelerating boundaries, as well as dispersive objects
in relative motion. A general (trace) formula is derived for the radiation from
accelerating boundaries. Applications are provided for objects with different
shapes in various dimensions, and undergoing rotational or linear motion.
Within this framework, photon generation is discussed in the context of a
modulated optical mirror. For dispersive objects, we find general results
solely in terms of the scattering matrix. Specifically, we discuss the vacuum
friction on a rotating object, and the friction on an atom moving parallel to a
surface.
1 aMaghrebi, Mohammad, F.1 aGolestanian, Ramin1 aKardar, Mehran  uhttp://arxiv.org/abs/1210.1842v201667nas a2200145   4500008004100000245006400041210006200105260001400167490000700181520123200188100002701420700001801447700001901465856003701484       2012                        eng d00aPolymer-mediated entropic forces between scale-free objects0 aPolymermediated entropic forces between scalefree objects  c2012/12/30 v863 a  The number of configurations of a polymer is reduced in the presence of a
barrier or an obstacle. The resulting loss of entropy adds a repulsive
component to other forces generated by interaction potentials. When the
obstructions are scale invariant shapes (such as cones, wedges, lines or
planes) the only relevant length scales are the polymer size R_0 and
characteristic separations, severely constraining the functional form of
entropic forces. Specifically, we consider a polymer (single strand or star)
attached to the tip of a cone, at a separation h from a surface (or another
cone). At close proximity, such that h<<R_0, separation is the only remaining
relevant scale and the entropic force must take the form F=AkT/h. The amplitude
A is universal, and can be related to exponents \eta governing the anomalous
scaling of polymer correlations in the presence of obstacles. We use
analytical, numerical and epsilon-expansion techniques to compute the exponent
\eta for a polymer attached to the tip of the cone (with or without an
additional plate or cone) for ideal and self-avoiding polymers. The entropic
force is of the order of 0.1 pN at 0.1 micron for a single polymer, and can be
increased for a star polymer.
1 aMaghrebi, Mohammad, F.1 aKantor, Yacov1 aKardar, Mehran  uhttp://arxiv.org/abs/1208.5778v200969nas a2200145   4500008004100000245006800041210006700109260001300176490000800189520052100197100002700718700002200745700001900767856003700786       2012                        eng d00aSpontaneous emission by rotating objects: A scattering approach0 aSpontaneous emission by rotating objects A scattering approach  c2012/6/70 v1083 a  We study the quantum electrodynamics (QED) vacuum in the presence of a body
rotating along its axis of symmetry and show that the object spontaneously
emits energy if it is lossy. The radiated power is expressed as a general trace
formula solely in terms of the scattering matrix, making an explicit connection
to the conjecture of Zel'dovich [JETP Lett. 14, 180 (1971)] on rotating
objects. We further show that a rotating body drags along nearby objects while
making them spin parallel to its own rotation axis.
1 aMaghrebi, Mohammad, F.1 aJaffe, Robert, L.1 aKardar, Mehran  uhttp://arxiv.org/abs/1202.1485v201641nas a2200193   4500008004100000245005000041210004900091260001500140300001600155490000800171520110300179100002701282700002401309700001901333700001701352700002201369700001901391856003701410       2011                        eng d00aCasimir force between sharp-shaped conductors0 aCasimir force between sharpshaped conductors  c2011/04/11  a6867 - 68710 v1083 a  Casimir forces between conductors at the sub-micron scale cannot be ignored
in the design and operation of micro-electromechanical (MEM) devices. However,
these forces depend non-trivially on geometry, and existing formulae and
approximations cannot deal with realistic micro-machinery components with sharp
edges and tips. Here, we employ a novel approach to electromagnetic scattering,
appropriate to perfect conductors with sharp edges and tips, specifically to
wedges and cones. The interaction of these objects with a metal plate (and
among themselves) is then computed systematically by a multiple-scattering
series. For the wedge, we obtain analytical expressions for the interaction
with a plate, as functions of opening angle and tilt, which should provide a
particularly useful tool for the design of MEMs. Our result for the Casimir
interactions between conducting cones and plates applies directly to the force
on the tip of a scanning tunneling probe; the unexpectedly large temperature
dependence of the force in these configurations should attract immediate
experimental interest.
1 aMaghrebi, Mohammad, F.1 aRahi, Sahand, Jamal1 aEmig, Thorsten1 aGraham, Noah1 aJaffe, Robert, L.1 aKardar, Mehran  uhttp://arxiv.org/abs/1010.3223v101014nas a2200157   4500008004100000245004500041210004500086260001500131300001000146490000700156520059200163100002700755700001800782700001900800856003700819       2011                        eng d00aEntropic force of polymers on a cone tip0 aEntropic force of polymers on a cone tip  c2011/12/01  a660020 v963 a  We consider polymers attached to the tip of a cone, and the resulting force
due to entropy loss on approaching a plate (or another cone). At separations
shorter than the polymer radius of gyration R_g, the only relevant length scale
is the tip-plate (or tip-tip) separation h, and the entropic force is given by
F=A kT/h. The universal amplitude A can be related to (geometry dependent)
correlation exponents of long polymers. We compute A for phantom polymers, and
for self-avoiding (including star) polymers by epsilon-expansion, as well as by
numerical simulations in 3 dimensions.
1 aMaghrebi, Mohammad, F.1 aKantor, Yacov1 aKardar, Mehran  uhttp://arxiv.org/abs/1109.5658v2